History of Protistology

Antony van Leeuwenhoek (1623-1723) 1674-1716 first reported protists, recorded in letters to the Royal Society of London.

Huygens 1678 ciliates observed

Buonami 1691 Colpoda and euglenoids

Harris 1696 Euglena

Joblot, 1718 treatise on microscopic organisms, disproved abiogenesis using infusions

Trembly 1744 division in ciliates

Hill, 1752 Paramecium named

Baker, 1953 found Noctiluca

Rösel von Rosenhof, 1755 Various protists

Wrisberg, 1764 coined the term "Infusoria"

Ellis 1769 trichocysts of Paramecium with Geranium juice

Eichhorn, 1783 Heliozoan Actinospherium

O.F. Müller 1773, 1786 Monographs on protists, ciliate drawings still valid

Lamark 1816 named Folliculina

Gruithusen early 1800's cyclosis

Goldfuss 1817, coined term Protozoa

d'Orbigny 1826 study of Foraminiferida

Ehrenberg 1828-1838 major works on protists, many names still valid

Dujardin 1835-1841 monograph on protists, coined Rhizpoda

Purkinje 1840 coined the term Protoplasm

Siebold 1845 distinct definition of "protozoa"

Müller 1858 Radiolaria

Perty 1852 Ciliata

Cohn 1853 Flagellata

Claparède and Lachmann 1858 Suctoria

Haeckel 1862 Heliozoa; 1866 Protista

Diesing 1865 Mastigophora

Stein monographs 1854, 1859 on Ciliata and Mastigophora

Leidy 1879 first comprehensive work on protists of North America "Freshwater Rhizopods of North America"

Stokes 1888 "The Freshwater Infusoria of the United States"

Fossil remains from the begining of the Cambrian 570 mya

Calculated divergence of Kinetoplastids: 1BYA

rRna Sequences data shows polyphyletic origin of protists

phyla or kingdoms?

36+ phyla proposed with 100, extant described species

Historical Bias

Descriptive research centered in europe/freshwater: cosmopolitanism

Many habitats and geographic regions not explored

protists not included in ecosystem level trophic dynamics until recently

 

Corliss, J.O. 1975. Three centuries of protozoology: a brief tribute to its founding father, A. van Leewenhoek of Delft. J. Protozool. 22:3-7.

Corliss, J.O. 1978-79. A salute to fifty-four great microscopists of the past: a pictoral footnote to the history of protozoology. Parts I & II. Trans. Amer. Micros. Soc. 97:419-458; 98:26-58.

Corliss, J.O. 1979. The Ciliated Protozoa: Characterization, Classification, and Guide tot he Literature, 2nd ed. Pergamon Press, Oxford & New York.

Corliss, J.O. 1986. Progress in protistology during the first decade following reeemergence of the field as a respectable interdisciplanry area in modern biological research. Prog. Protistol. 1:11-63.

Corliss, J.O. 1986. The 200th aniversary of "O.F.M., 1786": a tribute to the first comprehensive taxonomic treatment of the protozoa. J. Protozool. 33:475-478.

Dobell, C. 1932. Antony van Leewenhoek and his "Little Animals". Swets & Zietlinger, Amsterdam.

Montagnes, D.J.S., Taylor, F.J.R., & Lynn, D.H. 1990. Strombidium inclinatum n. sp. and a reassessment of Strombidium sulcatum Claparede and Lachmann (Ciliophora). J. Protozool. 37:318-323.

 

MICROSCOPY

Carl Zeiss (1816-1888)

Sir George Airy

Ernst Abbe (1840-1905)

Otto Schott (1851-1935)

August Köhler (1866-1948)

Lens grinding and microscope building was trial and error until Enrst Abbe figured out the physics of image formation by the lenses of the microscope

Airy and Abbe: diffraction theory of image formation:

Image formation not explained by geometric optics, only by wave theory of light. A spot will produce an image of a bright central disk (the Airy disk) and concentric rings of diffracted light. Resolution is detemined by the ability to separate airy disks, limited to 0.13 m for optical systems using white light.

Microscope objective images the light source and

changes in the light source image due to the specimen

Amplitude = Brightness

Wavelength = Color

Objects in microscope transparent, seen only if contrast background in intensity or color.

Object will deviate waves: change amplitude and shift phase

Numerical apeture of lenses = N.A. =i sine

i = refractive index of white light (wavelength 5890 A)

vacum

0

air

.0003

water

1.33

immersion oil

1.515

Flint glass

1.62

Crown Glass

1.52

Fluorite Glass

1.43

Diamond

(Red=2.41; Violet=2.47; Dispersion = 0.06)

Refractive index different for different wavelengths, dispersion.

Resolution = R = N.A./wavelength

Thus resolution is dependant on the wavelength of light and the N.A. of the objective.

Limit of resolution by light microscope = 0.24 m, max N.A. of 1.4

Dark field: Only waves deviated by the oject pass through.

Phase contrast: Object retarts waves 0.25 wavelength,

Bringing background, object deviated waves back into phase.

Differential Interference Contrast: using a prism to separate colors of deviated and undeviated waves.

Confocal Microscopy: Block out all deviated and undeviated waves above and below the plane of focus.

Epifluorescence Microscopy: Mercury Bulbs, observing objects below the limit of resolution by making them light sources

Scanning Laser Microscopy: Krypton-Argon laser, point scanned excitation.

Transmission Electron Microscopy: utilizing a smaller wavelength, magnetic lenses, degree of electron retardation by object.

Scanning Electron Microscopy: Reflected secondary electrons, surface imaging

Type

StereoScope

Compound

Scanning

Transmission

Wave Source

Light

Light

Electron

Electron

Useful Magnification Range

8-212 x

8-1250 x

14-50,000 x

200-500,000 x

Resolution (angstroms)

20,000 A

2,500 A

120 A

2 A

Resolution (micrometers)

2 m

0.25 m

0.012 m

0.0002 m

 

Anonymous. Basics of the Optical Microscope. Olympus Corporation, N.Y.

Gray, P. 1964. Handbook of Basic Microtechnique, 3rd ed. McGraw-Hill Book Co., N.Y.

Haugland, R.P. Molecular Probes (catalog). Handbook of fluorescent probes and research chemicals. Molecular Probes, Inc., Eugene, OR.

Hayat, M.A. 1981. Fixation for Electron Microscopy. Academic Press, N.Y.

Kemp, P.F., Sherr, B.F., Sherr, E.B., & Cole, J.J, eds. 1993. Handbook of Methods in Aquatic Microbial Ecology. Lewis Publishers, Boca Raton, FL.

Köhler Illumination Centenary, 1984. Reprints by the Royal Microscopical Society, Seacourt Press Ltd., Oxford. (Available from Zeiss, Inc.).

Möldner, K. 1983. Preparation Techniques for Electron Microscopy. Carl Zeiss, Oberkochen, West Germany.

Möllring, F.K. 1981. Microscopy from the Beginning. Carl Zeiss, Oberkochen, West Germany.

Murphy, J.A. & Roomans, G.M., eds. 1984. Preparation of Biological Specimens for Scanning Electron Microscopy. Scanning Electron Microscopy, Inc., O'Hare, IL.

Smith, R.F. 1987. A tribute: "The four horsemen of microscopy". Functional Photography Sept/Oct.

 

CELL BIOLOGY

Cytological Approach: function from structure

Biochemical Approach: function from in vitro and in vivo reaction products

Think Small- Think Unicellular Organisms

Molecular solutions that parallel Cellular solutions of metazoans.

Locomotion, feeding, digestion, osmoregulation

Characters of Living Cells:

1) complexity of structure

2) Change energy from one form to another: oxidation-reduction

3)Response to stimuli: plasticity and irritability

4) Homeostasis: maintain an inherently unstable system at some level of stability

5) Growth

6) Capacity to Reproduce

"the development, maintenance, modification and evolution of form" (Lynn, 1981)

Major components of cells:

10% protein

2-3% complex carbohydrates

2.0% lipids

1.1% nucleic acids

0.4% small organic molecules

1.5% inorganic ions

85% water

Protein and water: 10% solution gel or sol?

Some proteins crystalize at 20%, 10% should be viscous

Water in cell is not all free, bound up by proteins and molecules,

affects what compounds are disolved and where

Ground Substance of Cytoplasm: Porter & Tucker (1981, Sci. Amer.)

high voltage TEM: microtrabicular lattice: cytoplasm not a haphazard solution, Organelles held in place by a cytoskeletal system

Cytoskeletal system:

Microtubules

Microfilaments

Actin fibers

Microtubules:

Centrioles Observed in light microsocpy as bright "asters"

1960's electron microscopy revealed tubular nature

Highly conserved: Histones only proteins to have undergone less evolutionary change (Dales, 1972. J. Cell Biol. 52:748-753)

Nagleria gruberi has two immunologically distinct tubulins sets: flagella and basal bodies tubulin unique

2 globular proteins, 55 Kda each: tubulin alpha and beta dimers has greater electrophoretic mobility due to charge difference, guanine binding site locations differ

Microtubules will self assemble given GTP and both dimers

Each molecule binds with GTP, one GTP hydrolyzed

alpha + beta+ 2 GTP = alpha-beta-GDP + GTP

GTP exchanges with medium, GDP tightly bound

Both GTP and GDP remain associated with tubulin

Availability of Ca++ controls polymerization

Forms tubules with 13 protofilaments 5 nm diameter,

Tublules 24  2 nm in diameter, core 15 nm, subunits have a pitch of 10-25 degrees

50% of tubulin remains as monomers within the cell, equilibrium process, tubulin monomers recycled Cruder cell preps polymerize better: MAPS: microtubule associated proteins

Role in assembly of microtubules into structures, stability

Mammalian brain:37degC required for polymerization

Dissociation at 4deg C, flagella & cilia tubules stable

Euplotes from Antarctica (-1.8 to -2 C) has gene sequence differences in dimer binding site, very different than temperate species (Miceli et al., 1994)

MicroTubule Organization Centers (MTOC's)

(Pickett-Heaps, 1975. Ann. N.Y. Acad. Sci. 253:352-361)

Centrioles, Centrosomes:electron dense regions, bright "asters" under light microscope from eminating microtubules

Microtubular Structures

Tubular ribbons side by side (one to one) linkages: basal bodies, oral structures

Irregular hexigons: three or three pairs of linkages

Four linkages:

Six linkages: dense hexagonal packing, cytopharyngeal baskets of ciliate Nassula

Centrioles & Basal Bodies: nine triplet microtubules, 400 nm long,

0.15-0.25 m dia, One complete tubule, two10 subunit tubules attached

Tetrahymena basal bodies have a single strand of RNA by AO, RNAse

Role in mitosis

Microfilaments 4-5 nm thick, cell shape, attached to membranes.

Membranes:

Singer and Nicholson 1972 Fluid Mosaic Model

Lipid bilayer with traversing proteins (unit membrane 80 A)

Glycocalyx: glycoproteins, carbohydrates, sensory, solute transport functions

Golgi (dictyosome in plants): smooth membranes stains with Osmium & silver salt, acid phosphatase concentrated , processing of ER produced proteins into glycoproteins; glycocalyx, extrusomes, scales, lysomes may originate

ER: less lipid than golgi membrane, attached ribosomes make secreted proteins, may be continuous with nuclear and mitochodrial membranes

Ribosomes

Nuclear Membrane + one layer of ER = Nuclear envelope

Chloroplasts: Pigments, DNA, membrane layers

Mitochondria: laminar, tublular, pingpong paddle cristae, DNA

Lysosomes: hydrolytic (36 different) and acid phosphatase enzymes, single unit membrane; come from ER and golgi

Microbodies: Glyoxysomes & Peroxisomes

Glyoxysomes: Plant cells, conversion of lipid to carbohydrate, production of hydrogen peroxide: has catylase Glyoxylate Cycle

Peroxisomes: amino acid oxidases, production and removal of hydrogen peroxide.

Levels of organization (Lynn 1981): Structural Conservatism

Level of Organization

Structure

Organellar system

Locomoter system

Organellar complex

Kinetid

Unit organelle

Kinetosomet

Sub organelle

Microtubule

Macromolecule

Tubulin

Cell cycle

G1: diploid vegetative

S: centriole replication at begining, DNA replication throughout

G2: Quadraploid

mitosis/divsion

 

Porter, K.R. & Tucker, J.B. 1981. The ground substance of the living cell. Scientific American.

Lynn, D.H. 1981. The organization and evolution of microtubular organelles in ciliated protozoa. Biol. Rev. 56:243-292.

Giese, A.C. 1979. Cell Physiology. Saunders College Publishing, Philadelphia, PA.

Dustin, P. 1978. Microtubules. Springer-Verlag. Berlin.

Dales, S. 1972. Concerning the universality of a microtubule antigen in animal cells. J. Cell Biol. 52:748-753.

Pickett-Heaps, J.D. 1969. The evolution of the mitotic apparatus: an attempt at comparative cytology in dividing plant cells. Cytobios 1:257-280

Avery, S.V., D. Lloyd, and J.L. Harwood. 1994. Changes in membrane fatty acid composition and D12-desaturase activity during growth of Acanthamoeba castellanii in batch culture. J. Euk. Microbiol. 41: 396-

Jacobson, K., E.D. Sheets, and R. Simson. 1995. Revisiting the fluid mosaic model of membranes. Science 268: 1441-1442.

Ramesha, C.S. and G.A. Jr. Thompson. 1983. Cold stress induces in situ phospholipid molecular species changes in cell surface membranes. Biochimica et Biophysica Acta 731: 251-260.

Ramesha, C.S. and G.A. Jr. Thompson. 1984. The mechanism of membrane response to chilling. J. Biol. Chem. 259: 8706-8712

 

Evolution

In the protists "one finds the extreme adaptations of cell structure and organization, and by the study of some of the more bizarre forms we may gain some insight into the possibilities and also the limits of eukaryotic cell organization and specialization" Berger & Taylor, 1981.

One theory suggests there was a time when RNA served both genetic and catalytic functions (Joyce, 1991). Catalytic functions of RNA known, information content inherent.

DNA-protein life thought to have begun 4 bya

Between 4.2 and 4.0 bya environmental conditions became favorable for evolution of life, chiefly due to the fall off in level of meteor impacts

Organic soup formation is well understood, organic complexes and amino acids detected in meteorites

Jump from organic soup to self replicating life remains a mystery.

Fossils reveal life on earth 3.5 to 3.6 bya: stromatolites and microfossils

Stromatolites:phototrophic photoautotrophic, mucus sheaths = cyanobacteria 3,556 +/- 0.032 bya

First Eukaryote fossils in rock

possible at 2.1 bya

more probable at 1.5 bya

for certain at 1.2 bya

600 mya invertebrate-vertebrate split

530 mya Cambrian Explosion

400 mya Fish

300 mya Birds

Structural Inheritance

Inheretance of structure above the level of molecules independant of genetics

ciliate asexual reproduction: sex vs. reproduction segmentation of growing cylinders

Omins forma ex DNA: all form from DNA

Two different perspectives:

1) continuity of structural oganization: inheritance of phenotypic differences

2) indispensibility of preexisting structure for genesis of new structure:

physical rules that constrain and determine biological organization

Differences in number of ciliary rows is inherited in clones

Clones from a mixed population of 8’s and 9’s do not develop mixtures of 8’s and 9’s unitil many generations later

Figure 4.1: stability ranges for phenotypic variation: structural inheritance bounded by genetics:

Variability within stable region inherited for long periods,

extremes tend to fall back into stability region

Autonomy of ciliary rows:

inverted ciliary rows inherited for 800-1500 fissions

structure "...determined by the molecular geography within the unit territory and not by any other outside influence, either molecular or cellular"

Sonneborn (1970)

Character

Radiation

Divergence

Convergence

Conserved

Phylogenetics

Cladistics

Monophyletic: Single origin within a phyla

Paraphyletic: Single origin and not all descendants

Polyphyletic: Multiple origins within a phyla

Neutral mutations in sequence analysis

Protists are not "relicts" of the evolutionary process from prokaryotes to metazoa and metaphyta, they are evolutionary endproducts in their own right with comon ancestry with metazoa

Problems with protists:

1) extreme diversity

2) tremedous convergence of characters

3) symbiotic events

4) they have left very little fossil records

5) biochemcial data is lacking for many groups

Naegleria-like cysts in Cretaceous amber (Waggoner, 1993)

Lack of structural features and fossil record prevented evolutionary analysis of prokaryotes and hampered analysis of protists

Fossil record for those forms that create tests and loricae

Oceanic oozes >30% biogenic particles CaCO3 and SiO2,

mm's /year, km’s deep

 

Two ways to examine phyologeny of Protists:

Structural/Morphologic: Lynn (1981) Structural conservatism: "The conservation of structure through time is inversely related to the level of biological organization."

Biochemical/Molecular: rRNA, other genes, conserved proteins (enzymes)

Sequence homologies of conserved genes and proteins compared

Theories of eukaryotic origin:

archebacterial theory: based on 16s rRNA (Woese, 1987)

Methanogens, Halobacteria, Thermoacidophiles:

no muramic acid walls

actin and myosin-like molecules

DNA associated with a histone-like basic protein

Prolific symbionts in protists

Shared 11 amino acid sequence in highly conserved EF-1 alpha

Involved in protein synthesis (Hoffman, 1992; Rivera & Lake, 1992) other prokaryotes have a four amino acid sequence in this region EF-tu

Autogenous vs Serial Endosymbiosis

Autogenous:

Specialization and development of cellular compartments: membrane invaginations, mesosomes

Serial Endosymbiosis Theory (Taylor, 1974)

Lynn Sagin /Margulis

Origins with Portier (1918), Wallin (1927), Schanderl (1948)

co-metabolism, evolving atmosphere - O2 toxicity

requires translocation of genes from symbiont to host.

Predatory bacteria (Guerrero et al., 1986):

epibiotic attachment: Vampirococcus on Chromatium

penetration to periplasmic space: Bdellovibrio

Penetration of the cytoplasm: Daptobacter

Chloroplasts and mitochondria (Gray 1988) have:

prokaryotic -like DNA: more closely related to prokaryotes than eukayotes

Prokaryotic ribosomes

sensitive to antibiotics

Arise only from themselves: If cured Euglena plastids do not spontaneously reform

Polyphyletic origin?

Symbioses ( in the broadest sense) abound: Legionella, Chlorella

Chloroplasts:

cyanobacteria (a only), prochloron (a & b chlorophyl), no brown analog

Plastids with two memebranes: prokaryotic endosymbionts

plastids bearing more that two memebranes: endosymbionts were Eukaryotic

three membranes: euglenoids & dinoflagellates: Dinos with Peridinin have unique form of RiBisCO

previously only found in some Proteobacteria encoded in dino nuclear DNA: unique evolutionary history

four membranes: chlorophyll c containing organisms other than dinoflagellates

Symbionts:

Cryptomonad with "nucleomorph": double membrane bound with RNA & DNA (Douglas et al, 1991; Penny & O'Kelly, 1991)

nucleomorph, chloroplast and cytoplasm, eukaryotic ribosomes enclosed by chloroplast ER

when first described 25 years ago recognized that it might be endosymbiontic eukaryote

Nuclear rRNA close to fungi, Acanthamoeba, and green plants

Nucleomorph rRNA associated with red algae.

Ribulose biphosphate carboxylase enzyme DNA agrees with this placement

Crytpto chloroplast and red algae chloroplasts in a different clade than cyanobacteria, cyanelles, & green plant chloroplasts

Blue-Green dinoflagllate Gymnodinium acidotum contains a cryptomonad.

Ciliate Mesodinium rubrum has cryptomond (Wilcox & Wedemayer, 1985)

both symbionts lack periplast, ejectosomes, & flagella

Transformation stages of symbionts to chloroplasts

Amphidinium wigrense contains blue-green chloroplasts: three membranes, lack of any other non-dinoflagellate organelles, but chloroplast structure is typical of cryptophytes

further degeneration of symbiont

Dinos Peridinium balticum, Kryptoperidinium foliaceum contain Chrysophyceans

Mitochondria: Paracoccus, Rhodopseudomonas like bacteria

many cases of obligate bacterial symbioses in mitochondria free protists

rRNA phylogenies

Protist groups separated very early, with the most deeply divergent organisms belonging to orders of flagellates = ancient origin for 9+2 organelle, fungi, plants that lack flagella or centrioles are derived and developed other types of mtoc for mitotic spindle formation

Ciliates diverge late with Dinos, close to metazoan-metaphyte radiation

nuclear peculiarites probably derived: in ciliates nuclear dualism and two of the stop codons that are elsewhere universal code for glutamine, dinos lack histones.

Protists represent lineages from the transitions from prokaryote to eukaryote and unicellualr to multicellular organisms

as much or more distance between some flagellates and ciliates as between ciliates and metazoa

Trichomonas, a quadraflagellated mitochondria-less flagellate, diverges very early, suggesting a long period of eukaryotic life prior to the aquisition of mitochondria

Hydrogenosomes derived from mitochondria

Mitochnodrial genes found in the nuclues-gene transfer

 

16s rRNA (Hinkle & Sogin, 1993)

Radiation in eukaryotic lineages: rougly co-occurring divergences of plant, animal, Straemopiles and aveolate (dinoflagellate, ciliate, apicomplexan) Crown Eukaryotes

Incomplete understanding of the 16s-like rRNA clock speed makes dating difficult, but estimates of one billion years ago (Sogin, 1991) for eukaryotic radiation.

First eukaryotes were likely flagellates: all organisms at base of tree are flagellates, amoeboid forms convergent, arose numerous times Hinkle & Sogin (1993).

Classifications of Protists

Natural groupings based on presumed evolution:

Cladagrams common ancestry

Artificial but convienient

Natural Ecological functional

Sapropic system in Europe

Haeckel, 1866 three kingdoms:Plantae, Protista, Animalia

Whittaker: 5 kingdoms: Monera, Protista, Fungi, Plantae, Animalia

Levine et al., 1980 Subkingdom Protozoa in kingdom Protista

seven Phyla: Sacromastigophora

Labyrinthomorpha

Apicomplexa

Microspora

Ascetospora

Myxospora

Ciliophora

Cavalier-Smith, 1993

Empires: Bacteria, Eukaryota

Eukaryota Kingdoms: Plantae, Animalia, Fungi, Chromista, Protozoa, Archezoa;

18 Phyla

Corliss, 1994

same six kingdoms, 34 Phyla, 83 classes

eliminates many inter-level classfications

Evolution Bibliography

Baroin, A. et al., 1988. Patial phylogeny of the unicellular eukaryotes based on rapid sequencing of a portion of 28s ribosomal RNA. PNAS 85:3474-3478.

Britten, R.J. 1986. Rates of DNA sequence evolution differ between taxonomic groups. Science 231:1393-1398

Douglas et al., 1991. Crytomonad algae are evolutionary chimeras of two phylogentically distinct unicellular eukaryotes. Nature 350:148-151.

Gray, M.W. 1988. Organelle origins and ribosomal RNA. Biochem. Cell Biol. 66:325-348.

Guerrero, R. et al. 1986. Predatory prokaryotes: predation and primary consumption evolved in bacteria. PNAS 83:2138-2142.

Gutell, R.R. et al., 1994. Lessons from an evolving rRNA: 16s and 23s rRNA structures from a comparative perspective. Microbiol. Reviews 58:10-26.

Hinkle, G. & Sogin, M.L. 1993. The evolution of the Vahlkampfiidae as deduced from 16s-like ribosomal RNA anlaysis. J. Euk. Microbiol. 40:599-603.

Hoffman, M. 1992. Reserchers find an organism they can really relate to. Science 257:32.

Joyce, G.F. 1991. The rise and fall of the RNA world. The New Biologist 3:399-407.

Margulis, L. 1981. Symbiosis in cell evolution. W.H. Freeman & Co., San Francisco.

Penny, D. & O'Kelly, C.J. 1991. Seeds of a universal tree. Nature 350:106-107

Rivera, M.C. & Lake, J.A. 1992. Evidence that eukaryotes and eocyte prokaryotes are immediate relatives. Science 257:74-76.

Waggoner, B.M. 1993. Naeglaria-like cysts in cretaceous amber from central Kansas. L. Euk. Biol. 40:97-100.

Wilcox, L.W. & Wedemayer, G.J. 1985. Dinoflagellate with blue-green chloroplasts derived from an endosymbiotic eukaryote. Science 227:192-194.

Woese, C.R. 1994. There must be a prokaryote somewhere: Microbiology's search for itself. Microbiol. Reviews 58:1-9.

 

ZOOFLAGELLATES

Kingdom Archezoa (maybe should be in Kingdom Protozoa)

Widespread anaerobic/aerotolerant free living in organic rich habitats

Lack of golgi, mitochondria, peroxisomes

Uniflagellate amoebae ( Phylum Achamoebae)

Pelobiontea: single flagellum associated with nucleus cap of microtubules from base of basal bodies and covers part of nucleus; thin connections to nuc membrane flagella poorly motile

Pelomyxa, Mastigna, Mastigamoebae, Phreatamoebae, Mastigella

Tetraflagellate non-amoeboid (Phylum Metamonada) well developed cytopharynx and cytostome

Trepomonadea, Retortamonadea, Oxymonadea

Trepomonadea: Diplomonadida, Enteromonadida

Doublet organisms: 2 nucleii and 2 flagellar complexes, two cytostomes

Enteromonas:

occurs as single and doublet organism insertion on nuc. mem.

4 flagella per mastigont system, 3 anterior, one recurrent

Subnuclear Fiber: anterior to nucleus

Infranuclear Fiber: crosses under nucleus and descend along trailing flagellum of opposite side

Direct Cytostomal Fiber: descends posteriorly, surrounds cytopharynx

reduction or elimination of cytostome in more "advanced" forms

trailing flagella axonemes in these forms pass through cytoplasm to anterior

Giardia:

specialized adhesive organelles

mitosis semi-open with intranuclear spindle

nuclei divide synchonously

Free-living genera: Trepomonas, Hexamita

Trepomonas:

lateral insertion of mastigont systems

Cresant shaped nuclei

Grooved cytostomal pockets

one free flagellum, three descend through cytostomal groove

Supranuclear splays under plasma membrane

encystment

Retortamonadea

2 pairs basal bodies connected by striated fiber, basal bodies at right angles

heterodynamic flagella, one or 3 anterior, one trailing descending through a

Supranuclear fiber anterior to nucleus

Direct Cytostomal fiber posteriorly surrounds cytopharynx

Lacks infranuclear fiber

tube-like cytostome channel to the outside

cytostopharynx extends posteriorly to form funnel shaped depression, lips

Trailing flagellum has flattened vane like ridges.

cytostome and cytopharynx are stengthened by microtubules

Subsurface microtubules

No golgi, few membrane organelles except food vacuoles

mitotic spindle is intranuclear, nuclear membrane remains intact.

resistant cysts for transmission

Two free living genera:

Retortamonas: two flagella, salt marsh, cytostopharyns groove/pockets

Chilomastix: four flagella

Oxymonadea

may be related to retorts

2 pairs of basal bodies connected by thick fiber

ribbon of microtubules arises from this fiber and descends to posterior of cell joined by other ribbons to form a compound structure: the axostyle

Axostyle may bend actively, contractile, main form of locomotion

Anterior of cell supported by sheet of microtubules: pelta arises from one basal body

no golgi, no cytostome

posterior site of phagocytosis, pinocytosis known

mitosis closed, intranuclear spindle

 

Phylum Percolozoa

Phylum Parabasalia

Not resolved whether branch is before or after Euglenozoa

Trichomonadea: difference between two species as great as vertebrate classes

endozoic, have parabasal bodies: golgi + striated fiber

Trichomonas

cytoskeleton of microtubules and striated fibers, parabasal fibers, costa, attractophores,

parabasal fibers: arise from anterior most basal body, descend either side of the nucleus, support two golgi

Costa: underlies and supports undulating membrane, thick striated fiber

Attractophores (rhizoplasts) extend from a basal body to the nuclear envelope

lack mitochondria, contain basilliform hydrogenosomes: two membranes, contain DNA

lack cytostome, posterior phagocytosis and pinocytosis

glycogen storage

closed mitosis with external spindle, kinetochores inserted in nuclear membrane

Ditrichomonas hornigbergii: free living anaerobe trichomonad. Suggests features are not specializations of parasitic/commensal life Farmer (1993)

Pseudotrichomonas: free living

Phylum Euglenozoa

Euglenoidea

Kinetoplastidea

kinetoplast:polymerized AT rich DNA in single mitochondrion.

20% of nuclear DNA, largest chunk of extranuclear DNA known

polymerized small circles and some larger circles more typical of mitochondrial DNA

single chunk near basal bodies or several dispersed

divides before nucleus

1 or 2 flagella from a pocket or pit, paraflagellar rod

single mitochondrion extends length of cell, basal bodies associated with mitochondrion not nuclear membrane

microtubule cytoskeleton

microtubule supported cytopharynx

singular nucleus, prominent nucleolus, persists through mitosis

golgi in region of flagelar pocket but not attached

CV if present empties into flagellar pocket

rRNA suggest close relatives of Euglenoidea:

heterodynamic flagellaw/ paraxial rods

flagellar pocket w/cv

unitary mitochondrion

pellicular microtubules

microtubule supported pharynx

closed mitosis

Orders Bodonida & Trypanosomatida

Bodonids:

small 3-15 um bacterivores and plant pathogens

oval or elongate with two heterodynamic flagella arise from an anterior flagellar pocket, no expanded flagellar pocket reservoir

flagella smooth, or with non-tubular mastigonemes, sometimes in tufts

paracrystalline paraflagellar rod in each flagellum adjacent to axoneme

Longitudinal microtubules under plasma membrane

Some forms have a well developed cytostome opening near anterior of cell

supporting microtubules originating adjacent to basal bodies

contractile vacuole empties into flagellar pocket

single golgi

single mitochondria with kinetoplast and ping-pong paddle cristae

mitosis closed with internal spindle, binary longitudinal fission

Trypanosomes

parasites of blood and tissues of plant and animals.

single flagellum, two basal bodies

epimastigote, trypanomastigote stages free swimming

flagellum connected to cell body with undulated membrane

amastigote flagellum reduced and non-emergent

nutrition aquired by phagoccytosis at base of expanded flagellar pocket

transmission by sucking insects, complex life histories

African sleeping sickness, Chaga's disease, Leishmaniasis

 

Phylum Choanozoa: class Choanoflagellatea

mostly marine

single anterior flagellum, collar of slender cytoplasmic tentacles form a collar or basket

no mastigonemes, may have vane like projections

cytoskeleton of subsurface microtubules extend from basal bodies

no rhizoplast or stirated fibers

flattened cristae possible affinity to chrysomonads

secreted stalks common, loricae of organic or thin silica rods

Cortico-Flagellates: Katablepharis, Colponema

Ciliate like flagellates

Phylum Opalozoa

tubular cristae, cortical aveoli, rigid tubular mastigonemes

endozooic flagellates in amphibians

flattened, taper posterior

multiple flagellar apparati arranged in kineties, some short, do not extend length of cell

two striated fibers directed to the left of basal bodies (kd to the right in ciliates)

mts only arise from the basal bodies of the falx, extend between kineties in cytoplasmic ridges

pinocytosis between ridges

numerous diploid nucleii

cell divides longitudinally

Stephanopogon

thought to be remant of primitve ciliate ancestor

small <20 um resemble karyorelecteans

free living, marine sediments, bacteria, diatoms, flagellates

cytopharyngeal area

Kineties

homokaryotic, multinucleate, longitudinal division in cysts,

each product binucleate

Infraciliature unique, resembles some flagellates

discoidal cristae

no aveoli, pc or t mts, kds, parasomal sacs

 

Brugerolle, G. 1993. Evolution and diversty of amitochondrial zooflagellates. J. Euk. Microbiol. 40:616-618.

Dodge, J.D. 1979. The phytoflagellates: fine structure and phylogeny. In: Levandowsky, M. & Hutner, S.H. 1979. Biochemistry and Physiology of Protozoa. Vol 1:7-58

Farmer, M.A. 1993. Ultrastructure of Ditrichomonas honigbergii N.G., N.SP. (Parabasalia) and its relationship to amitochondrial protists.

Farmer, M.A. & Triemer, R. 1994. An ultrastructural study of Lentomonas applanatum (Preisig) N.G. (Euglenda). J. Euk. Microbiol. 41:112-119.

Foissner, W., H. Blatterer, and I. Foissner. 1988. The Hemimastigophora (Hemimastix amphikineta nov. gen., nov. Spec.), a new protistan phylum from Gondwanian soils. Europ. Jour. Protistiol. 23:361-83.

Lee, R.E. & Kugrens, P. 1992. Relationship between flagellates and the ciliates. Microbiol. Rev. 56:529-542.

Lee, R.E. & Kugrens, P. 1991. Katablepharis ovalis, a colorless flagellate with interesting cytological characteristics. J.Phycol. 27:505-513.

Lipscomb, D & Corliss, J.O. 1982. Stephanopogon, a phylogenetically important "ciliate", shown by ultrastructural studeies to be a flagellate. Science 215:303-304.

O'Kelly, C.J. 1993. The Jakobid flagellates: structural features of Jakoba, Reclinomonas and Histiona and implications for the early diversification of eukaryotes. J. Euk. Microbiol. 40:627-636.

Patterson, D.J. 1993. The current status of the free-living heterotrophic flagellates. J. Euk. Microbiol. 40:606-609.

Patterson, D.J. and Larsen, J. 1991. The Biology of Free-living Heterotrophic Flagellates. Systematics Association Special Volume No. 45, Clarendon Press, Oxford, UK. 505 pp.

Schnepf, E. & Elbrachter, M. 1992. Nutritional strategies in dinoflagellates. A review with emphasis on cell biological aspects. Europ. J. Protistol. 28:3-24.

Sleigh, M. 1979. Contractility of the roots of flagella and cilia. Nature 277:263-264.

Suzaki, T & Williamson, R.E. 1986. Pellicular Ultrasructure and euglenoid movement in Euglena ehrenbergii Klebs and Euglena oxyuris Schmarda. J. Protozool. 33:165-171.

Triemer, R.E. & Fritz, L. 1987. Structure and operation of the feeding apparatus in a colorless Euglenoid, Entosiphon sulcatum. J. Protozool. 34:39-47.

Viscogliosi, E., et al. 1993. Phylogeny of Trichomonads based on partialsequences of large subunit rRNA and on cladistic analysis of morphological data. J. Euk. Microbiol. 40:411-421.

Wessenberg, H. 1966. Observations on cortical ultrastructure in Opalina. J. Microscop. 5:471-492.

 

SARCODINES

"lacking useful phenotypic characters for comparative analysis, amoebae are a classic example of a highly paraphyletic group of protists tradditionally united in taxonomic schemes universally recognized as artificial."

Hinkle & Sogin, 1993

Growing sentiment that taxon Sarcodina is not valid

Formation of pseudopods shared with leukocytes, dinoflagellates,

many cellular forms

Pseudopodia:

Lobose

Filose

Granuloreticulose: anastomosing networks

Actionopods: rigidly cross linked microtubules

endoplasm:granular

ectoplasm, hyaloplasm: clear,

in actinopoda, reticular network surrounding cell

Uroid

Limax (tongue shaped), mono or polypodial, finger shaped etc

Most amoebae small 5-50 microns with one or few lobopodia or filopodia

Most information from Amoeba proteus and Chaos carolinenesis

three types of nuclei:

1) Spherical to discoidal, sometimes dented or folded, nucleoli (endosomes) scattered throughout or near the nuclear membrane: Amoeba proteus

2) Spherical with central nucleolus: Nagleria, Entamoeba

3) Spherical with one or more eccentric nucleoli: Polychaos, Iodamoeba

Presence of nucleus required for locomotion: enucleate half cells round up, move again after reintroduction of nucleus.

Amoebae proteus nucleus: trilaminar porous membrane with honeycomb support matrix internal

nuclei can be removed and inserted into other amoebae with high rate of survival

Surface membrane covered with plasmalemma: glycocalyx integrated with membrane, fibrous protrusions, scales, spines, frothy vesicles

Mitochondria have tubular cristae

Plasmalemma (sarcolemma): protection, adhesion, sensory reception, chemical detection, alterations of chemical balances

Filaments: anionic, sensitive to positively charged substances: blockage with nuetral red or alcian blue prevents pinocytosis, proteases destroy ability of Chaos to recognize prey

filaments may be piezo-electric: mechnoreceptors

Some crystals (unknown) and lipids storage

Triuet crystals (urea) accumulate unitl divsion-presumable used as nitrogen source for nucleic acid production

Contractile vacuole in freshwater amoebae, rarely in marine

Golgi site of plasmellemma formation, scale and test plates

Testate amoebae (both filo and lobopodia)

Shell formation:

1) proteinaceous, 2) agglutinate, 3) silicious secreted, 4) calcareous secreted

older shells accumulate minerals and become darker

Some amoebae (Euglypha & Paulinella ovalis make scales, store them near nucelus until cell divsion, scales donated entirely to daughter cell, adults do not replace lost scales Ions that inhibit silica deposition (germanium) block scale formation. Selective ingestion of siliceous particles also donated to daughter cell. If daughter separated from parent after transfer of nucleus and scales, assembly of test will proceed: genetic mechanisms seem to determine shell formation: used as a taxonmic criterion

Cytoskeleton: actin fibers network. Attached to the inner lamina of cell membrane

myosin links to actin Ca++ dependant contraction

Cysts may be mucilagenous, cellulosic, proteinaceaous or all three.

Giant amoebae Chaos carolinense emits an anesthetizing substance for prey ciliates

some amoebae secret enzymes to extracellularly digest bacteria

Mitosis:

1) metamitosis-nuclear membrane disintegrates, amphiastral spindle forms, membrane reconstructed during telophase

2) mesomitosis- nuclear membrane persists through part of mitosis, spindle has neither astral poles or polar caps

3) promitosis- dome shaped half cups of divided endosome form poles of spindle, envelope persists

Immune response: nuclear transplants from an amoeba that has not recovered from a cytoplasmic bacterial infection to an enucleated amoeba that has developed resitance cannot prevent reinfection.

Special cases:

Pelamyxa palustris (vanBruggen et al., 1988): Archezoa: primitively lack mitochondria, golgi, mitotic spindle, mtoc, any 9+2 arrangement.

Methanogenic symbionts (and others).

Entamoebae: lacking mitochondria, peroxisomes, hydrogenosomes.

Small if any golgi, parasitic, some glycogen storage

Slime Molds: thought to be closely related to soil amoebae, aggregation and fruiting body stages with spores (Hartmanella + Protostelids)

Protostelids:amoeboflagellates; Acrasids: lobose, eruptive pseudopods

Myxogastrea: acellular slime molds, Physarium

Dictyostelea: cellular slime molds: Dictyostelium

Nagleria: amoeboflagellates, cells change from amoeboid form with no obvious polarity to elongate flagellated form by de novo synthesis of basal bodies

Foraminefera

Exclusively marine Most benthic, some planktonicgranulorecticulopods

most multinucleate:

1)vegetative or somatic, irregular, eliptical, amoeboid protrusions, many peripheral nucleoli, fibrous inner surface to membrane, many pores

2) generative smaller, fewer pores, few central nucleolei

microtubules in pseudopods, branching tubules into reticular networks

cross bridges react with antibiodies to atpase dynein molecules of cilia

Goltz & Hauser, 1994

Shell is "external" but covered by cytoplasm

fibrous plasmellema. May include bubble vesicles for floatation, sticky fibrous coat on reticulopods

Peroxisomes and lysosomes, mitochondria occur in the reticulopods.

Each filopd retains its identity in bidirectional cytoplasm (granular, rheoplasm) motion despite fusion in bundles of reticular networks (anastomoses): constant motion of the cytoplasm through out the reticulonetwork and cell body in shell

each filopod contains coiled core of microtubultes and microfilaments.

microtubules and bidirectional flow establish tension in reticulopods

Shell distinctive most calcium carbonate , some agglutinated

Digestion initiated along reticular network, with fusion of lysosomes (gastriole), completed in cell body

prey opn unicellualars or meiofauna

Life cycle: 1) Agamont: does not produce gametes, develops from zygote

2) Gamont: develops from agamont, meiotic divsions, gametes are amoeboid or flagellated, shellless

temporary pseudocysts

Actinopods axiopodia stiff with rigid cross-linked microtubules

also possess reticulopods

Heliozoa:

few with mineral skeletons, few with ecotplasm, mostly freshwater

nucleus can be deformed by axopods

Nucleus has fibrous layer on outside of membrane, nucleoli around periphery, some multinucleate,

axoneme contains two whorls of microtubules of variable length, tapers microtubules oringinate at the surface of the nucleus. Cell memebranes extends out and along each axopod with extrusomes and mitochondria

surface covered by sticky mucus

some cysts known

axopods range from few microtubules to extremely complex from MTOC's, give radiate shape.

MTOC's can be

1) plaques on nucleus surface,

2) plaques on an interior dense layer of cytoplasm,

3) single central centroplast, ,

axopods can provide locomotory function

bidirectional flow of cytoplasms along axonemes, saltatory movement controlled by localized changes in the ion balance across the cytolasmic membrane

may "row" or "walk" on axonemes

trap prey by adhesion to axopods, retratction draws prey to cell body, large lobopod extends from cell body to form gastriole

binary fission, some swarmers, cell fusion known

Radiolaria

nuclei with central endosome, nucleolus has eccentric clear globule

cytoplasm clearly delineated from outer vesicular cytopplasm by organic membranous boundary caled central capsule, enclosed by complex "endoskeleton" of strontium sulfate (Acantharea) or opaline silicates (Polycystinea, solid spines & Phaeodarea, hollow spines, organics)

central capsule surrounds nucleus and axoplast, pores through capsule connect ecto and endoplasm. axoplast (MTOC) near nucleus, microtubules radiate out through fusules into axopods ectoplasm organized into a mass of reticulopods.

mucus or gelatinous coat

some cysts known

cytoskeletons simple to elaborate

in Acantharea, spines anchored in an ectoplasmic cortex, myophrisks (cups) elastic and contractile

cytoplasmic movement continual bidirectional along axopods and throughout ectoplasm

Many with algal symbionts

digestion similar to forams with gastriole forming on reticulopods

multiple mitotic fission with biflagellate swarmers in acantaria

polycystinia swarmers from endomitoses and and fragmentation of the nucleus, swarmers may have crystal of strontium sulfate, some binary fission

Phasodaria binary or multiple fission

 

Hinkle, G. & Sogin, M.L. 1993. J. Euk. Microbiol. 40:599-603.

Vahlkampfiidae:

Ability to transform from amoebae to flagellates, One mode usually predominates: Nagleria mostly amoeba;

Tetramitus mostly flagellate

eruptive motility, closed mitosis with dividing nucleolus, cyst

formation

Name from genus Vahlkampfia (only member not to form flagellates)

Only other amoeba-flagellate is myxomycota (plasmodial-acellular

slime molds)

By 16s rRNA, Monophyletic group that branches early

Nagleria splits early

Acanthamoeba diverge within the "grand radiation of eukaryotes"

Entamoeba emerges much later, related, but not significantly clustered

with Vahlkampfiids

Patterson, 1983. Nuclearia moebiusi J. Proto 30:301-307

Filose pseudopodia without mts, homogeneous cytoplasm in Pseudopods

Mitochondria with flattened cristae

Lacks extrusomes, MTOC's, cytoplasmic mts

mts inside nucleus only during mitosis

reorganization of nuc envelope late in division

Pattern of cellular organization unique from other amoebae

ill-defined genus due to small number of characters

Classification by pseudopod type: Class Filosea, includes testaceans

naked filosea in two families Vampyrellidae and Nucleariidae based on feeding behavior

Only other group with flattened cristae is centrohelid heliozoa

Nuclearia lacks extrusomes, cytoplasmic mts, mtoc and surface structures of that group

Caan, 1986. Nuclearia delicatula J. Proto 33:392-396.

ingestion of Phormidium, pentration of Spirogyra,

but not at cross wall junction

finely pointed and filose pseudopodia can branch but do not anastomose

fine pointed pseudopods in diretion of motion , hyaline zone of cytoplasm

filopods not from hyaline cytoplasm

mesomitotic nuclear division, intact nuclear membrane

contractile vacuole pattern unique, small spherical vesicles enlarge around CV prior to CV filling.

 

Chavez et al, 1986. Phreatamoeba balamuthi n.g., n.sp. J. Proto. 33:397-404

Anaerobic or microaerophilic amoeboflagellate but different from others by eruptive limax locomotion, polymorphism, multinucleate

flattened locomotive form with broad anterior hyaline zone like mayorellid Paramoebidae, Conodina, but flagellate and multinucleate

Multinucleate forms in Pelobiontida

other amoeboflagellates in Schizopyrenida which locomote by hemispherical hyaline eruptions, nucleolus and nuclear membrane persist during division.

P.balamuthi nucleoulus breaks down

Flagellate stage lacks rostrum, collar, and cytostome of other amoeboflagellates

Like Naeglaria gruberi and Adelphamoeba cannot reproduce as flagellate

Cone like microtubular structure associated with flagellar basal bodies suggests an affinity to the Eumycetozoa: intermeadiate between "true" amoebae

van Bruggen et al., 1988 Methanogens in Pelamyxa palustris. J. Proto 35:20-23.

P. palustris lacks golgi, mitochondria, mitotic apparatus, mtoc, 9+2

Patterson 1985. J. Protozool. 32:241-246. Pompholyxophrys punicea

Spherical bodied amoebae with fine radiating pseudopods considered a heliozoan

Layer of siliceous spheres "pearles"

rare organism not culturable

no extrusomes, cytoplasmic microtubules, or microtubular axonemes as found in heliozoa

acentric nucleus, mitochondria, nuclear dictyosomes superficial layer of homogeneous cytoplasm continuous with filopods

feeding by ingestion

Shares these characters with the Nucleariid amoebae

Golz & Hauser, 1994.

reticulopod networks contain highly ordered regions of microtubules and less structured arrays.

Structural MAPs occur in the loosely arranged tubule regions

Ordered arrays connected by ciliary dynein-like proteins

reacts with ciliary dynein ATPase antibody-motor proteins for microtubules

 

Bibliography

 

Anderson, O.R. 1983. Radiolaria. Springer-Verlag, Berlin. 355 pp.

Anderson, O.R. 1996. The physiological ecology of planktonic sarcodines with applications to paleoecology: patterns in space and time. J. Euk. Microbiol. 43:261-274.

Caan, 1986. Nuclearia delicatula J. Proto 33:392-396.

Caron, D.A., A.F. Michaels, N.R. Swanberg and F.A. Howse. 1995. Primary productivity of symbiont-bearing planktonic sarcodines (Acantharia, Radiolaria, Foraminifera) in surface waters near Bermuda. J. Plankton Res. 17: 103-129.

Chavez et al, 1986. Phreatamoeba balamuthi n.g., n.sp. J. Proto. 33:397-404

Espanosa-Cantellano, M. et al., 1998. Entamoeba dispar: ultrastructure, surface properties and cytopathic effect. J. Euk. Microbiol. 45:265-272.

Goltz, R. & Hauser, M. 1994. Europ. J. Protistol. 30:221-226.

Hülsman, N. 1993. Lateromyxa gallica N.G., N.Sp. (Vampyrellidae): a filopodial amoeboid protist with a novel life cycle and conspicuous ultrastructural characters. J. Euk. Microbiol. 40:141-149.

Patterson, 1983. Nuclearia moebiusi J. Protozool. 30:301-307

Patterson 1985. J. Protozool. 32:241-246. Pompholyxophrys punicea

Röpstorf et al., 1994. Comparative fine structureal investigations of interphase and mitotic nuclei of Vampyrellid filose amoebae J. Euk. Microbiol. 41:18-30.

Sawyer, T.K. et al. 1998. Learamoeba waccamawensis, N.G., N.Sp. (Heterologosea: Vahlkampfiidae), a new temperature=tolerant cyst-forming soil amoeba. J. Euk. Microbiol. 45:260-264.

Stothard, D.R., et al., 1998. The evolutionary history of the Genus Acanthamoeba and the identification of eight new 18S rRNA sequence types. J. Euk. Microbiol. 45:45-54.

van Bruggen et al., 1988 Methanogens in Pelamyxa palustris. J. Proto 35:20-23.

Weekers, P.H.H. et al., 1993. Effects of grazing by the free-living soil amoebae Acanthamoeba castellanii, Acanthamoeba polyphaga, and Hartmanella vermiformis on various bacteria. Appl. Environ. Microbiol. 59:2317-2319.

Yamaoka, I et al., 1984. Scale formation in an amoeba, Cochliopodium sp. J. Protozool. 31:267-272.

 

Ciliates

"Indeed, amoung the protists, ciliates have taken subcellular specialization to its limit."

Lynn & Corliss, (1991)

Most complex cellular archetecture of all known eukaryotes

Archetecture of ciliature and infraciliature, oral apparatus

used to distinguish groups:

tendancy for decreased polymerization:

less but more specialized oral structures

historically, patterns of ciliation on somatic and oral surfaces used.

Cell division complex: most binary but many variations

dikaryotic: macronucluei, micronuclei

amicronucleate forms known

endomitosis, intact membrane, internal microtubules in some

external in others: heterotrichs and Karyorelecteans

macs and mics divide, except Karyorelecteans,

in which macs can only come from mics

Hammerschmidt et al., 1996: Karyorelectians not relects

Karyorelects and heterotrichs sister group with all other cilia

Two subphyla proposed:

Postciliodesmatophora Gerrassimova and Seravin 1976:

Mac division evolved with external mac spindle

Intramacronucleata subphylum nov.: internal mac spindle

Mac divsion evolved with internal spindle

most phagotrophic: cytostome-cytopharynx, oral kinetids, cilia, cytoproct-cytopyge

contractile vacuole-nephridial plasm

extrusomes: mucocysts, toxicysts, fibrous trichocysts

divsion binary or multiple, some complex in suctoria and chonotrichs

Cortex:

somatic: locomotion, attachment, protection, sensing

oral: capture and ingestion of nutrients

infraciliature:basal bodies (kinetosomes) and associated fibrils

Kinetid: Kinetodesmal fiber KD, Transverse and Postciliary microtubular ribbons

mts and fibers link adjacent kinetids into kineties

Class Heterotrichida

somatic dikinetids with anterior or both ciliated

well developed overlapping pc ribbons

conspicuous right or left handedness to oral structures

Oral polykinetids traverse anterior and extend into an oral cavity.

Fused somatic cilia in some = cirri

some loricate, sessile forms

left serial polykinetids may encircle anterior end

external microtubles in mac mitosis in some

may be primitve branch from ciliate radiation

some loricate forms Folliculina, Stentor

Class Amophorida (position uncertain)

Anaerobic Metopidae, Caenomorphidae

Class Karyorelictea

Formerly thought to be "primitive" ciliates.

long, vermiform, thigmotactic, many with one barren surface

extremely contractile, marine interstitial, one genus freahwater

pc ribbons overlap

macs contain aprox 2x mic DNA but composition unknown

Macs do not divide

Postciliodesmata present

Generally lack corical aveloi

Protocruzia single large chromosome condenses in mac,

may be all chromosomes end to end,

cytophoran oral structure, kinetid and karyo type

Often found in marine anerobic, microaerophilic and sufurous conditions

Kentrophorous, Tracheloraphis: only known pseudopodial feeding

Loxodes Anaerobic, has Mullerian vesicles

Class Litostomatea

Little specialization of cilia surrounding the mouth

somatic kinetid of one kinetosome + 2 transverse ribbons

one lateral into cortex

one anterior

mt nematadesmata extend into cytoplasm from bases of dikinetids that surround the cytostome: rhabdos

subclass Haptoria carnivores, protistovores: toxicysts

Didinium, Lacrymaria, autotrophic mesodinium

subclass Trichstomia:Entodiniomorphorphicds:

endosymbionts of vertebrates

Balantidium only human ciliate parasite

Class Prostomatea

Oral apparatus at or near apical part of cell

Relatively simple oral ciliature, may be simple polykinetids = brosse

many have litostome like toxicysts

monokinetids on somatic surface, transverse mt ribbons oriented radially

Prorodon, Coleps, Metacystis

class Spirotrichea

Subclass Oligotrichia

conical or bell shaped body

somatic cilia poorly developed

Oral polykinetids surround anterior end, used for locomotion and feeding

Tintinnids, Strobilidiids, Strombidiids

Subclasses Stichotrichia and Hypotrichia

Dorso-ventrally flattened

somatic cilias as rows or scattered polykinetids Cirri

Benthic, cirri used as walking appendages

Class Colpodea: radiation mirrors ciliate radiation

oral morphology diverse, resemble many other groups:

prostomes, oligohymenophoreans, nassophoreans, heterotrichs

reticulate silverline system

somatic stomatogenesis

somatic dikinetid kinetid distinct, with transverse mt ribbon extending from posterior of dikinetids toward posterior of ciliate forming a desmos

Oral ciliature in right and left fields

terrestrial, freshwater, many edaphic

division cysts, slime mold ciliate

Class Nassophorea

Oral nematodesmata, can be quite elaborate

mono & dikinetid with tranverse ribbon tangential,

well developed KD, may have kd desmos

feed on filamentous cyanobacteria

Nassula

Class Phyllopharygea

prominant radially arranged mt ribbons that form the cytopharynx.

somatic monokinetids transverse mts reduced or absent,

distinctive lateral KD

somatic kineties underlain by subkinetal mts

Phyllophryngia: free living, commensal and parasitic forms

Chonotrichia: ectocommensals on crustaceans

Suctoria: only larval forms ciliated

"adults" also have kinetosomes-unciliated

tentacles with haptocysts sessile free floating some with stalks

most suck out contents of prey, one penetrates

Reproduction by budding "Birthing"

Class Oligohymenophorea

most speciose of the ciliates

usually three oral polykinetids to left or anterior of cytostome,

ODK membrane (Paraoral, Undulating) on right

somatic monokinetids, some dikinetids,

radially directed transverses,

anterior only in dikinetids directed tangential

overlapping kinetodesmata

mucocysts common

Subclasses

Peniculinia

buccal cavity with PO + peniculi and quadrulus

oral nematodesmata

somatic dikinetids

explosive trichocysts

freshwater

Frontonia, Paramecium, Lembadion

Scuticociliata

mono and dikinetids, dikinetids sometimes restricted to posterior half

Paraoral dikinetid in three segments, third is stomatogenic

caudal cilium

chondriome in some species

Uronema, Pleuronema

Hymenostomatia: hymenostomes

somatic monokinetids, right most post oral kinetid stomatogenic

Oral ciliature UM + AZM

Tetrahymena, Ichthyophthirus

Astomatia: mouthless symbionts in anelids and amphibians

may have holdfast appendage

Peritrichia: prominant oral ciliature encircles anterior end

somatic cilia reduced: telotroch band on larvae

stalked sessile bacterivores vorticella, some loricate, colonial,

strongly contractile stalks, Vorticella, Zoothamnium, Opercularia

"mobiline" Trichodina

Apostomatia:

ectosymbionts with complex life cycles

tied to physiology of marine crustacean hosts

 

Bibliography

Baroin-Tourancheau, A. et al., 1992. A broad molecular phylogeny of ciliates: identification of major evolutionary trends and radiations within the phylum. PNAS 89:9764-9768.

Corliss, J.O 1979. The Ciliated Protozoa. Characterization, classification, and guide to the literature. 2nd Ed. Pergamon Press, New York. 455 pp.

Hammerschmidt, B., M. Schlegel, D.L. Lynn, D.D. Leipe, M.L. Sogin, & I.B. Raikov. 1996. Insights intothe evolution of nuclear dualism in the ciliates revealed by phylogenetic analysis of rRNA sequences. J. Euk. Microbiol. 43:225-230.

Kurtz & Tiedtke 1993. J. Euk. Microbiol. 40:10-13.

Lynn, D.H. 1996. My journey in ciliate systematics. J. Euk. Microbiol. 43:253-260.

Small, E.B. & Lynn, D.H. 1981. A new macrosystem for the phylum Ciliophora Doflein, 1901. BioSystems 14:387-401.

Small, E.B. & Lynn, D.H. 1985. Phylum Ciliophora Doflein, 1901. Pp 393-575 In: Lee, J.J., S.H. Hutner, & E.C. Bovee, eds., An Illustrated Guide to the Protozoa. Society of Protozoologists and Allen Press, Lawrence, KA.

 

Symbioses:

Any in or on another: mutual to parasitic

Establishment of Symbionts:

1. Breakage & loss of phagosomal membrane: free in cytoplasm

2. Loss or inactivation of Lysosome receptors

3. Non-digestion after fusion of lysosome

1 & 2 common

Symbiont: codes for all structural and functional molecules needed

Organelle: some sequence (genes) transferrred to host,

transport of products required

Mitochondria: 4 destinations: OM, IM, Periplasmic Space, Matrix

Chloroplasts: 5 destinations: thylakoid

multiple membrane layers in some protists: higher complexity

Review by Lee et al., 1985

Algal symbionts:

synchronous division common

predominantly ciliates and amoebae

Fresh water :Chlorophyceae mostly more common than cyanobacteria: Cyanelles

Marine:Chlorophysceae, Rhodophyceae, Dinophyceae, Bacillariophyceae

Chlorella in Paramecium

EM observations of Chlorella: indistigusihable from free living form

Physiological differences in carbon metabolism and release of photosynthate

Few substances released: carbohydrates:fructose, glucose, xylose, maltose,

some amino acids

Released carbon can be 85% of photosynthetically fixed carbon

Release is pH dependant, energy consuming process

Released carbohydrates not detected within cells in high amounts

higher specific activity of ribulose-1,5-biphosphate carboxylase

All symbionts examined are in perialgal vesicles, not free in the cytoplasm

divided symbionts each enclosed separately

divide synnchronously with host

Different from food vacuoles:

Vacuoles: only one alga per vacuole

small space 0.05 um between alga and membrane

do not circulate

do not fuse with lysosomes

no acid phospahtase activity

exogenously supplied symbiont cells ingested and digested

cell surface properties and ability to translocate sugar important to infectivity

Carbon

In darkness, algae grow heterotrophically and maltose secretion is reduced

growth rate of symbionts slow relative to free living ones: maltose release

lytic enzymes of host may be lower when alga population high

Nitrogen

ammonia and glutamine provided by host

higher symbiont loads at higher light levelsresult in higher ingestion rates of particulate food: nitrogen demand on host.

Photoaccumulation of cells, not observed for free symbionts or symbiont free hosts

ciliary reversals controled by symbiont population requires >50 chlorella

Mesodinium rubrum red ciliate with Cryptomonad symbionts, mouthless

Chloroplast retention:

planktonic cilaites, benthic forams, freshwater Heliozoa

can be 40% of ciliate asssemblage in marine waters, mixotrophic

isolated chloroplasts quickly die, but functional in ciliate cytoplsm up to 2 weeks

chloroplasts do not divide

algal cells digested but not chloroplasts, free in cytoplasm

chloroplasts from several algal species can be held, some ciliates more restricted

may contribute 30-40 % of ciliate's carbon requirements

some obligate mixotrophs, chloroplasts are not digested during starvation

planktonic cilaites, benthis forams, freshwater Heliozoa

Zooxanthellae Gymnodinium dinos

Flagellate Leptomonas escapes food vacuole and penetrates host nucleus

Leptomonas found in Paramecium and Euplotes

 

Bacterial Associations

epibionts common on all types of free living flagellates, ciliates and amoebae: Microbial Seascapes

Flagellate epibionts

termite flagellates

Devescovid trichomonads

Metachonal waves of attached spirochetes on Mixotricha

specialized attachment structures provided by the flagellates

Sulfate reducers common

Cytoplasmic, Macronuclear, micronuclear

Legionella: normal host is free living bacterivorus protists will not grow in tap water, filtrates of tetrahymena culture, or lysed cells of Tetrahymena,

Kappa or "killer" particles, lambda, mu, gamma

gram negative bacteria in Paramecium aurelia

lambda provides essential folic acid

Kappa: : Caedibacter

N particles (non-brights) some fraction of which become Brights with R-body

ability to kill paramecia is due to R-body or ribbon that pierces food vacuoles

stimulated by low pH

viruses associated with extruded R-body

viruses induce formation of R-bodies in N particles

R-body production dependant on a plasmid

R-bodies similar to ejectosomes in Cryptomonads

similar structures seen in free living bacteria (Proteus sp.)

Epibiotic bacteria on Euplotidium

external cells in matched depressions, honey comb like array around the cell

two types: with and without ejectable ribbon

ejectable filament up to 20 x length of cell

stains with DAPI on tip: Viruses?

Nuclear bacteria

found in many protists: may contribute to host metabolism by providing required compounds or vitamins

common in termit flagellates: Caryococcus

Holospora in Paramecium: uncultivatable but by PCR amplification

back testing with fluorescent probes

found to be related to  subclass of the proteobacteria

closest relative is Rickettsia

short form: reproductive stage

long form: infective stage

Jeon 1992. Amoeba proteus strain with obligate bacterial symbiont

gram negative rod shaped bacteria in symbiosomes

three proteins and LPS from bacteria invovled in stability of the relationship.

29kD protiein in host cytoplasm

96 KD protein and LPS in symbiosome membrane Antigenic portion of LPS exposed on cytoplasmic face of symbiosome:prevention of lysosome fusion

Actin produced by the host accumulated by bacteria

Protein spectrin (220-225 kD) associated with symbiosome membranes

 

Methanogen associations common in rumen

and free living anaerobic protozoa:

utilizing H2 that inhibits protist metabolism

Hydrogenosome/methogen couplings

F420 coenzyme autofluorescence

Hydrogensomes: conversion of pyruvate to acetate and hydrogen

marker enzymes: ferridoxin oxidoreductase and hydrogenase

tolerant of oxygen at physiological levels

possible secondary development of mitochondria in some protists:

primitively anaerobic: Archezoa:Trichomonads, Diplomonads, microsporidia

secondarily anerobic:

in anaerobic Cyclidium hydrogenosme resembles mitochondriome of Uronmea

has methogens, and unidentified eubacterium in three part consortium

Embly and Finlay: anaerobiasis arose three times independnatly in ciliates

16s rRNA analysis of cilaites and symbionts

 

Bibliography

Amann, R., Springer, N., Ludwig, W., Görtz, H-D., and Scleifer, K-H. 1991. Identification in situ and phylogeny of uncultured bacterial endosymbionts. Nature 351:161-164.

Ball, G.H. 1969. Organisms living on and in protozoa. In Chen, T.-T., ed., Research in Protozoology Vol 3:565-718.

Embly, T.M. and Finlay, B.J. 1994. The use of small subunit rRNA sequences to unravel the relationships between anaerobic ciliates and their methanogen endosymbionts. Microbiology 140:225-235.

Esteban, G., Guhl, B.E., Clarke, K.J., Embly, T.M., and Finlay, B.J. 1993. Cyclidium porcatum n. sp.: a free-living anaerobic scuticociliate containing a stable complex of hydrogenosmes, eubacteria, and archeobacteria. Eur. J. Protistol. 29:262-270.

Fields, B.S., Shotts, E.B. Jr., Feeley, J.C., Gorman, G.W., Martin, W.T. 1984. Proliferation of Legionella pneumophila as an intracellular parasite of the ciliated protozoan Tetrahymena pyriformis. Appl. Environ. Microbiol. 47:467-471.

Fenchel, T and Finlay, B.J. 1991. The biology of free living anaerobic ciliates. Europ. J. Protistol. 26:201-215.

Fenchel, T. and Ramsing, N.B. 1992. Identification of sulphate-reducing ectosymbiotic bacteria from anaerobic cilaites using 16s rRNA binding oligonucleotide probes. Arch. Microbiol. 158:394-397.

Finlay, B.J. and Fenchel, T. 1989. Hydrogenosomes in some anaerobic protozoa resemble mitochondria. FEMS Microbiology Letters 65:311-314.

Fokin, S. and Görtz, H-D. 1993. Caedibacter macronucleorum sp. nov., a bacterium inhabiting the maconucleus of Paramecium duboscqui. Arch. Protistenkd. 143: 319-324.

Görtz, H-D. 1983. Endonuclear symbionts in ciliates. Int. Rev. Cytol. suppl 14:145-176.

Jeon, K.W. 1992. Macromolecules involved in the amoeba-bacteria symbiosis. J. Protozool. 39:199-204.

Lee, J.J., Soldo, A.T., Reisser, W., Lee, M.J., Jeon, K.W., and Görtz, H-D. 1985. The extent of algal and bacterial endosymbioses in protozoa. J. Protozool. 32:391-403.

Lindholm, T. Mesodinium rubrum- a unique photosynthetic ciliate. Adv. Aquat. Microbiol. 3:1-48.

Reisser, W. 1986. Endosymbiotic associations of freshwater protozoa and algae. Prog. Protistol. 1:195-214.

Stoecker, D.K. M.W. Silver, A.E. Michaels, and L.H. Davis. 1988. Obligate mixotrophy in Laboea strobila, a cilaite which retains chloroplasts. Marine Biology 99:415-423.

 

Locomotion :

"Animal behavior is largely governed by biological electricity"

Saimi et al., 1988. TIBS 13:304-309.

Four "known" motility systems

microtubule+ dynein + ATP

Bacterial flagellin

actin + myosin + ATP

spasmonemes

Cilia and flagella

0.2 m diameter

cilia 10's m long, flagella 100's m

cilia oar like motion

flagella more complex patterns

membrane controls motion

all eukaryotic cilia and flagella depend upon the same basic mechanism

motility, food gathering, behavioral response, cell recognition

9+2 axoneme surronded by membrane=specialized compartment of cytoplasm

doublet axonemal microtubules:

complete A subfiber, partial B subfiber c subfiber only in basal body

during self assembly, A fibers assemble above basal body, b sub fiber and other components assemble on A fibers

9 doublets linked into a ring by inner and outer dynein arms, radial spokes, interdoublet circumferential links.

several hundred known proteins in cilia, only a fraction have been identified

Cartwheel proteins of the basal body have been isolated by self assembly Gavin et al., 1994

Dynein: 9 polypeptides including 2 ATPases per arm

arms extend from A fiber to adjacent b fiber

radial spokes composed of 17 polypeptides

extend from A fiber to towards central complex (two microtubules and associated proteins)

Modeled as a cape, main body, and spherical head

Dynein activity must be regulated temporally and spatially to generate bends

Radial spokes invovled in regulating mt sliding:

Chlamydomonas mutants lacking radial spokes Smith & Sale 1992.

paralized or impaired motility

isolated axonemes can be induced to slide apart in telescopic fashion:

sliding disintigration assay.

sliding velocities diminished in axonemes missing radial spokes

restored by addition of isolated radial spokes from wild type flagella

radial spokes apparently interact with inner dynein arm

 

Switch Point hypothesis for control of doublet sliding:

one half on during power stroke, other half on during recovery.

Normal motility:

ATP and Mg2+maintained at 100 

Ca2+ at 10-7 M or less

 

Ciliary motion can change as

1) orientation reponse: direction of the power stroke changes counter clockwise in proportion to membrane depolarization: Ca concentration in cilia

2) Frequency respnonse: change in beat frequency in response to membrane hyperpolariztion

Chemically skinned cells ecxtracted with triton X-100

mixture of ATP, Mg swims forward

increasing addition of Ca results in counterclockwise shift in orientation

Hyperpolarization: adding K results in clockwise shift and beat frequency increase

Beating mechanism:

1) initiation of active sliding at the basal region

2) propagation of active sliding along the doublet pairs tot he tip

3) determination of the patterns of cross-bridging activity

Orientation mechanism: changing the patterns of cross bridging

Ca does not appear to affect beat frequency, only bridging patterns that affect orientation and indirectly affect beat frequency

 

Electrophysiology

Machemer, 1988

Ca2+ gradient 104:1 in, +116 mV

K+ gradient 40:1 out, -93 mV

net electrical potential -33 mV

energy expended in maintainingelectrical potentials

two major membrane conductances (up to 22 ion channels have been identified):

calcium and potassium

Calcium "calcium channel" excitation of membrane, rapid activation of cilary motor response. Only depolarization activates Ca channels

Potassium three types of channels with different acitvations on directly Ca activated

K channels are antagonists of Ca channels, maintain homeostasis

voltage dependant Ca channels on cilia only

depolarization of membrane by a few millivolts opens ciliary Ca channels

Ca influx triggers K channels for K outflow

In Bursaridium action potetnials are not graded, but all or nothing responses that are apparently spontaneous. Berg & Sand 1994

Chemokinesis

as eukaryotic cells exhibit irritabilty: response to external stimuli

Jennings 1906: the avoidance reaction

1. concentration threshold for response

2. responses to stimuli mediated by avoidance reaction: accumulation or dispersal

3. cells collect in areas of optimal stimulation by treating lesser stimuli as repellants:

attraction and repulsion are relative

an attractant can be a repellant relative to a stronger atractant

a repellant can be an attractant relative to a stronger repellant.

Van Houten: attaction saturatable and specific

Klinokinesis: modulation of turning or tumbling frequency

Orthokinesis: modualtion of speed

Most attractants for Paramecium found in the fermentation products of its food.

Didinium attracted to bacterial products

Specific chemical receptors have been identified for folate, cAMP

Amino acids induce hyperpolarizations in the nM range

work with Tetrahymena has shown that not all amino acids are attractants

Flagellate and amoebae responses to bacteria are variable: speciies dependant

Ca influx and binding to calmodulin associated with cAMP and cGMP formation. can be overridden by cAMP that accumulates as cells starve

Mechanoreceptors

anterior : depolarization, ciliary reversal

posterior: hyperpolarization speed up

posterior receptor channels may be selective to cations: aallowing only K+ flux

mechanoreceptors on soma membrane, not cilia membranes

cilia may physically transmit mechano stimuli to soma

Photoaccumulation:

peak at 520 nm photosynthesis peak at 440 and 680,

not inhibited by photosynthesis blockers

440 induces hyperpolarization (blue)

520 (green) and 680 (dark red) depolarization

photodispersal in white light and accumulation in dark: mechanism not understood

 

 

Microhydrodynamics

low reynolds numbers: ration of viscous to inertial forces

shear gradients from non-slip zone near surface to no-effect zone away from surface

the extent of influence of a cilium on the surrounding water limited by its proximity ot cell surface: net transport of water by the motion of a cilium

metachonal waves a function of mechanical hydraulics, not electrophysiology

 

Amoeboid motility

Cytoplasm partioned into two distinct regions: viscous hyaline ectoplasm and less viscous ganular endolasm

layer of microfilaments associated with boundary and plasma membrane

one filament 5-8 nm in diameter-actin continuously distributed over cell surface

thick filaments myosin containing in region of uroid

filaments in intermeadiate and uroid regions randomly oriented

filaments in frontal region paralell to plasma membrane.

Two major theories of amoeboid motility:

1) ectoplasmic tube contraction model

2) frontal contraction model

ectoplasmic "toothpaste" tube model: pressure exerted all over cell, especially at uroid, released at poit of pseudopodial advancement

suction on uroid does not stope pseudopodial formation

laser ablation of uriod does not stop pseuodopodial advancement.

frontal contraction model:flow produced by conversion of endoplasm into a gel-like state at frontal zone, producing a pull on the endoplasm.

modified thoery may be more accurate:

pressure exerted all over cortex, separation of filaments from membrane at frontal zone allows membrane expansion, granuloplasm filtered through the mesh of filaments, filaments depolimerize, allowing endoplasm to advance

reformation of membrane attached filaments from monomers in endoplasm

Filopodia cytoplasmic streaming and extension mt dependant

membrane markers dmeonstrate that membrane flows tractor tread like,

attachment to substratum can occur: adhesive "micropodia" leave "footprints"

Motility in coccidian Toxoplasma and other apicomplexans

Mondragon et al., 1994

twirling, gliding motility, rotation of the cell around a fixed posterior

inhibited by cytochalasins: drugs that interfere with actin filament function.

insensitive to colchicine mt drugs

mild proteolysis permeabolizes cells, inducing response

 

References

Berg, T.O. & Sand, O. 1994. Spontaneous all-or-nothing action potentials in the ciliate Bursaridium difficile. J. EuK. Microbiol. 41:13-17.

Dunlap, K. 1977. Localizaiton of calcium channels in Paramecium caudatum. J. Physiol. 271:119-133.

Eckert, R. 1972. Bioelectric control of ciliary activity. Science 176:473-481.

Gavin, R.H., Duffus, W.A., & Contard, P.C. 1989. Charateristics of basal body cartwheel reassembly. J. Protozool. 36:391-397

Levandowsky, M & D.C.R. Hauser. 1978. Chemosensory responses of swimming algae and protozoa. Int. Rev. Cytol. 53:145-210.

Machemer, H. 1988. Electrophysiology. Chapt 13. in Gortz, H.-D. Paramecium. Springer Verlag.

Machemer, H.D. 1988. Motor control of cilia. Chapt 4. in Gortz, H.-D. Paramecium. Springer Verlag.

Mondragon, R., Meza, I., & Frixione, E. 1994. Divalent cation and ATP dependant motility of Toxoplasma gondii tachyzoites after mild treatment with trypsin. J. Euk. Microbiol. 41:330-337.

Naitoh, Y. & Ekert, R. 1969. Ionic mechanisms controlling behavioral responses of Paramecium to mechanical stimulation. Science 164:963-965.

Ogura, A. & Takahashi, K. Artificial deciliation causes loss of calcium-dependant responses in Paramecium. Nature 264:170-172.

Satir, P. 1974. How cilia move. Scientific American 231:44-52.

Smith, E.F. & Sale, W.S. 1992. Regulation of dynein-driven microtubule sliding by the radial spokes in flagella. Science 257:1557-1559.

Van Houten, J. 1979. Membrane potential changes during chemokinesis in Paramecium. Science 204:1100-1103.

Van Houten, J & Preston, R.R. 1988. Chemokinesis. Chapt. 18. in Gortz, H.-D. Paramecium. Springer Verlag.

Symposium on the Structure and Function of Cilia and Flagella. J. Protozool. 31:7-40

 

Feeding and Growth

Pinocytosis

binding and channel formation

Induction by binding to acidic groups of the mucopolysaccharides of the glycocalyx

Group one: very labile inorganic salts at neutral pH

Group 2: Reversible bound proteins at pH giving positive charge

Group 3: irreversible bound Alcian blue dyes-binding to surface coat

Phagocytosis:

Food vacuole formation: binding of membrane dicoidal vesicles to ribbed wall to feed growing vacuole, Ca+ dependant actin polymerization

cycling of food vacuoles: selective digestion-cell wall materials of bacteria not digested, etc.

Stimulation of Phagocytosis

Common stimuli for phagocytosis found for amoebae, ciliates, and mammalian cells: conserved underlying biochemistry.

Binding to membrane triggering actin polymerization and food vacuole formation

lipids found to be effective Bailey et al., 1987..

lectins: Pseudomonas lectins stimulate phagocytosis in Tetrahymena

Bacteria fed Tetrahymena express a glycoconjugate not seen in axenic cells, derived in mucocysts

Mucous coat on amoebae capable of concentrating proteins and inorganic cations 10-50 x over the medium

Mechanical stimulation found to be necessary if chemcial receptors saturated

Changes in the structure of water at surfaces: ion displacement

Hormones:

peptide hormones and neuroppetides have been detected in bacteria and protists

biogenic amines: catecholamines, serotonin in:

Tetrahymena, Crithidia, Entamoeba

In Tetrahymena- cell divsion, glucose metabolism, regeneration of cilia can be regulated with biogenic amines

Histamine, serotonin, and epinephrine stimulate phagocytosis

andrenergic receptor antagonists block these responses

Conserved receptor, chmosensory transduction system:

receptor:guanine nucleotide binding protein adenylate cyclase

(GTPase, G- protein) generation of cAMP as a messenger

Dinoflagellate feeding

Particle feeding: sieving

optimal particle sizes: size selection demonstrated:

clearance rates and ingestion

filtration models discount selective capture or chemical recognition

however, not all bacteria support growth of protists: Later

1) preingestion recognition and selective feeding

2) selective digestion of randomly ingested particles

Also filtration models suggest water flow

between cilia of ODK, Collar tentacles of Choanoflagellates.

Chemical responses: gradients of particles and substrates

Bacterivory

Life History Attributes:

size changes

encystment

macrostome-tomites

amoebae communication cAMP & small oligopeptide: Glorin

Energetics:

Maintenance energy

For Human cells % of ATP:

Protein turnover 34.7%

Na+/K+-ATPase 19.0%

Ca2+ dependant processes 27.8%

RNA synthesis 8.5%

DNA sysnthesis 7.6%

Growth

Gross vs net assimilation effciency

For protists: growth and reproduction continuous phenomena

unlike metazoans:

growth to sexual maturity then energy expendture in reproduction

reproduction still as single cells!

Respiration: µ Mb, µ for metazoans 8x protists, b 0.75

Banse, 1982 MEPS 9:281-297

Amoebae

Crawford et al., 1994.

14C labelling method

high energetic cost of motility in amoebae: 56% of total metabolic activity

cytochalsin inhibited actin polymerization

Fenchel and Finlay estimated 1%, probably too low

10% for fast moving ciliates: may be more effcient than amoebae

Respiration rate may vary 50-60% for protists depending on nutritional state

respiration rate slows rapidly with starvation.

Chemical communication in amoebae

Small molecular weight molecules, taxa specific act as chemical messengers for "social amoebae".cAMP and Glorin a oligopeptide

Predator defense:

toxins, physical impediments

Lambornella clarki: free-living cilaite feeds on bacteria, mosquito larvae prey on l. clarki. Water soluble compound from mosquito larvae induces divsion of L. clarki to form parasitic cells that encyst on larvae, penetration of the cuticle occurs and ciliates eat mosquito larvae from inside. May eliminate mosquito larvae and reappear as free living cells

two species of Euplotes spine/"wing" development: Water soluble factors (polypetides) produced by a number of predators (ameobae, Lembadion, Stenostomum). Protein sysnthesis necesary for change but not cell divison. Cost of 15% of generation time, presence of a predator defense that is inducable indicates an increased survivorship with defense, but cost of maintaining defense when not needed.

 

Biochemistry

plantlike characteristic s and animla like characteristcs , as well as unique metabolic capabilities are found mixed throughout the protists

some photorophic and symbiont carrying forms have very few requirements, synthesizing all or most organics form inorganic materials

some parasitc forms are dependant on hosts for preformed organics

some dependance on preformed organic nitorgen is seen

amino acids, fatty acids, vitamins required by many protists

Nitrogen Metabolism

Ammonium preferred,but many phytofalgellates can use nitrate

Nitrate reductase (nitrate to nitrrite) also present in ciliate Loxodes

(Bacterial symbiont?)

most protist can ssimilate amino acids, and nucleotides, mostly from particulate food

urea is not produced

Lipids:

some sterols required for growth

Tetrahymena and other ciliates do not produce any typical sterols but produce Tetrahymenol, a pentacyclic triterpenoid

Tetrahymena can accumulate other sterols from medium and incorporate them in membranes, added chloesterol blocks tetrahymenol production

gamma linoleic acid found in Chryomonads, but not prymnesiomonads:

Suuports separation of these groups

Acanthanamoeba has amoung its major fatty acids 20 carbon polyunsaturates like higher animals, but also can biosynthesize long chain fatty acids de novo like plants

Lipid compositions are known to change with physiological state, temperature, and pressure adaptations

Enzymes

Rumen and termit gut protists have cellulase (symbionts?)

Acanthamoeba also has a cellulase: but may be for cellulosic cyst walls rather than digestion of celluose as a substrate

Collagenolytic activity found in some pathogenic amoebae, but not non-pathogenic forms

 

References

Bailey, G.B., Day, D.B., Nokkaew, C., & Harper, C.C. 1987. Stimulation by target cell membrane lipid of actin polymerization and phagocytosis by Entamoeba histolytica. Infect. Immun. 55:1848-1853

Bolivar, I., Guiard-Maffia, J. 1986. Expression of surface coat glycoconjugates by bacteria-fed Tetrahymena. J. Protozool. 33:335-340.

Bonner, J.T., 1983. Chemical Signals of Social Amoebae. Scientific American 248:114-120.

Crawford, D.W., Rogerson, A., Laybourn-Parry, J. 1994. Respiration of the marine amoeba Trichosphaerium sieboldi determined by 14C labelling and Cartesian diver methods. Mar. Ecol. Prog. Ser. 112:135-142.

Dive, D. 1973. La nutrition holozoique des protozoaires cilies. Ses consequences dans l'epuration naturelle et artificielle. L'Annee Biologique XII:343-380.

Fenchel, T. 1986. Protozoan filter feeding. Prog. Protistol. 1:65:114.

Fenchel, T. & Finlay, B.J. 1983. Repiration rates in heterotrophic, free-living protozoa. Microb. Ecol. 9:99-122.

Gilboa-Gardinaer, N & Sharabi, Y. 1980. Increase in growth rate and phaocytic acitivty of Tetrahymena induced by Pseudomonas lectins. J. Protozool. 27:209-211.

Kusch, J. 1993. Induction of defensive morphological changes in ciliates. Oecologia 94:571-575.

Levitzki, A. 1988. From epinephrine to cyclic AMP. Science 241:800-806

Washburn, J.O., Gross, M.E., Mercer, D.R., & Anderson, J.R. 1988. Predator-induced trophic shift of a free-living cilaite: parasitism of mosquito larvae by their prey. Science 240:1193-1195

 

Ciliate DNA

Cells studied: Paramecium, Tetrahymena, Stylonichia, Oxytricha, Euplotes

Nuclear dualism: germ line, somatic

Mating cells exchange haploid nuclei, develope new macronuclei

numbers of nuclei vary with species, multinuclei genetically identicle

mitosis intranuclear, individual chromosomes not identifiable

forms with multi macs fuse macs prior to mitosis

Karyorelecteans: no amitosis, mac derived at each divsion

switching mics and macs, phenotype determined by genes in mac

small amount of rna sythesis found by autorads in mics, but only during brief DNA sysnthesis period

genetic silence does not jibe with experimental removal of mics: lower asexual reproductive rates, no vegetative growth, cell death, although some forms survive well in amicronuc state

few mic specific genes eliminated in formation of mac, may escape deletion

some DNA sequences have been found in amicronucleate macs that are normally only found in mics

retention of essential vegetative genes in mic ensures survival of sexually competent cells

Mic structure: no nucleoli, uniform dense packed chromatin

Mac: chromatin bodies dispersed in nucleoplasm, multiple nucleoli, numerous nuc mem pores

Histones reflect other evolutionary data reflectin not only the ancient split from eukaryotic line but also extensive divergence witin the cilaites

in mics: genes in single copy: even rRNA gene, unlike other eukaryotes

Tetrahymena: DNA content of MAC 7.5-13.2 e9 bp in stable cultures, may vary more in different physiological conditions. Mac is a subset of sequences in mic

aprox. 46 x haploid mic (Paramecium: aprox. 800x): but not strictly polyploid. Mic 80% unique sequences, 20% repititous and eliminated (hypotrichs up to 98% repititious and deleted)

Aprox. 6000 cut/splice sites where sequence deletion occurs

deletions 10o bp to 10kbp, distribited thoughout 5 chromosomes

some deletions are interstitial tandem repeats of telomere sequence

(5'-dC4dA2-3')

may be as inverted repeating pairs defineing ends of transposable units excised and destroyed

functions of deleted sequences not known

mic DNA cut into permananet sub-chromosomal fragments

mic chromosomes average 44,000kbp

fragmented into 200 molecules 100 to over 1500 kbp at average of 57 copies/molecule

Telomeric repeates added to ends of molecules by Telomerase: provide stability and replication

rRNA 21 kbp molecule formed from excision of single rRNA gene, replicated and spliced into a palindrome telomeric sequences added both 17 and 25 s RNA encoded

Palindrome relpicated 9,000 molecules of 18,000 copies of the gene, aprox 300x other genes

telomeric sequences 20-70 tandem copies

transcription from center outward

Paramecium rRNA in molecules of various sizes with one to several genes arranged head to tail

Three Global changes identified with mac formation:

1) repititous sequences and some unique sequences deleted and destryed

2) 5 chromosomes fragmented in specific and repaetable pattern into aprox 200 molecules

3) each molecule replicated to an average of 57 copies

Hypotrichs

mac formation phenomena more extreme and slightly different

Mac to Mic DNA ratios: Euplotes crassus 27:1, 200:1 e. eurytomus

in Oxytricha and Stylonichia, 96 and 98% of mic DNA eliminated

mic DNA in Oxytricha is 70% unique sequences and 30% repeats

most of the unique sequences eliminated in mac formation, small subset of mic genes used in mac formation yet alre all that is necessary for vegetative growth

each sequence in mac aproximately 1900 copies in Oxytricha, 7500 copies in Stylonichia

high rates of transcription necesary for large, complex cells

rRNA gene in 1000,000 copies per mac

average of 950 for other molecules

Telomeres havesingle stranded overhangs of 16 to 20 bases, may interact to form circles or end to end associations: 4 stacked layers of G quartets hydrogen binding not known if this occurs in vivo

protein associations prevent double stranded exonuclease activity.

Replication of genomes

Mac & Mic replication separately regulated

Mics replicate rapidly, perhaps multiple replication origins, many deleted with mac formation macs may only have one or less per gene sized molecule

Macs: replication bands- wave of replication of milions of DNA molecules

pulse labeling: indicates dan in a gel state: labels a small band.

Prior to amitosis, dna sols, mac rounds up (multiples fuse) pulse labeled DNA mixes

nucleoii do not label

at least three replication band specific proteins that migrate with it

selective replication may also occur to maintain constant copy number of gene in mac

Tetrahymena DNA A+T rich, 76%, codoing regions only 56% spacer regions >76%

Hypotrichs: 75% for leaders, 69% for trailers, 52% for coding regions

Evolutionary drifting of non-coding sequences toward A+T richness is widespread amoung eukaryotes

Genetic code unique to ciliates

three universal stop codons in other eukaryotes: TAA, TAG, TGA have evolved different usage in ciliates, mostly glutamine coding, may be restricted to some genes

reflected in tRNAs

Tetrahymena: three glutamine tRNAs: two that reconize "stop" codons may have evolved from convential glutamine tRNA

Euplotes: TAA, and TAG used a s astop codon, TGA encodes cysteine

unusual condon useage may limit viruses: no viruses have ever been found in ciliates

other Codon usage is biased relative to other eukaryote usage

Two actin genes cloned from Oxytricha both code for 375 amino acid actin but are only 63% similarbut very different from actin conserved through yeasts & mammals

sequences are scrambled in micronuclueus relative to their final position in macronucleus 9 MDS separated by IES

three of six cloned genes from oxytricha have been scrambled in mic.

 

Amoebae: rRNA genes amplified as extrachromosomal circular molecules in Entamoeba histolytica

may be common feature of unicellular eukaryotes to have amplified genes as extrachromosomal elements

 

Trypanosomes

Genome undergoes frequent rearrangement permitting cells to avoid immune response by spontaneously changing surface coat.

Genome contains over 1000 genes encoding variant surface glycoproteins (VSG)

usually only one expressed at a time with aprox 107 copies of the protein on the surface, 5% of total protein, large for surface protein

Expression site associated genes (ESAG) also transcribed with VSG, 14 to 25 isogenes, glycoproteins, 0.01% of total protein, function unknown

Rearrangements by maneuvering VSG genes into expression sites for transcription

Several expression sites may exist, but only one active

Infection progresses in waves, 2 week intervals

sequential clone growth

From the N- terminal, 1st 25-30 amino acids different

successive peaks in a single rabbit resulted in 100 different VSGs

spontaneous switching at a rate of 10-6 to 10-7 per division, occurs in defined media, not a response to immune attack : unique genetic mechanism

protist chromosome number cannot be determined by staining because they do not condense sufficiently during mitosis to be visualized.

In Insect 1x, bloodstream 2 x

mixture of trypanosomes in insect phase may result in 1.5 x cells, twice the number of minichromosomes

pulse field electrophoresis: four size classes of chromosomes, some quite small for eukaryotes

VSG gene on a 80 kb minichromosome

100 minichromosomes 50-100 kb

5-7 200 to 700 kb; several 2000 kb

Some do not enter gel: very large or unusual structure

Chromosome size and number may vary within clones:

may fragment and fuse

minichromosomes less prominant in species that do not undergo antigenic variation

DNA probes hybridize to all chromosome sizes, several hundred to 1000 genes may exist

mRNA's contain 1600 bases, may be 4% OF genome

transpositional unit 2500 to 3500 bp, up to 9% of genome involved

transcriptionally regulated: VSG cDNA hybridizes only to RNA from tryp expressing that VSG and not to other Tryp RNA

Duplicative Transposition ELC formation

In some cases an extra copy of the transcribed gene is present:expression telomere linked copy more suseptable to DNAse cleavage

Switch to another VSG gene results in loss of the previous ELC

Telomere linked genes do not have to be duplicated for expression

All expression sites are next to telomeres: those genes internal must be copied and translocated to a telomere-linked expression site.

Transferred region replaces the previous segement in the expression site.

Most expresision sites located on large chromosomes

VSG genes may occur within sequences of 2 to 10 isogene families

Four possible acitivation events

1) ELC formation

2) teleomere exchange

3) teleomere conversion

4) switched activation without DNA transposition

Composite ELC's found with contributed elements from previosly active gene and others

 

Transcription in Tryps

Spliced leader sequence of 39 nucleotides at 5' end of all tryp mRNA, also found in non-variable kineto's

spliced leaders come from different locations than transcribed genes: Discontinuous Transcription

possible function:

1) transport across nuc membrane

2)stability of mRNA

3)trnaslation initiation

4) cytoplasmic compartmentalization

spliced leaders also found in nematod Caenorhabditis elegans, vaccinia virus

May be multiple promoter sites, some transposed, some upstream of transposed DNA

 

References

Bhattacharya, S. et al., 1989. Circular DNA of Entamoeba histolytica encodes ribosomal RNA. J. Protozool. 36:455-458.

Lee, S.Y., Lee, S.T., & Chang, K.P. 1992. Transkinetoplasty- a novel phenomenon involving bulk alterations of mitochondrion-kintoplast DNA of a trypanosomatid protozoan. J. Protozool. 1992. 39:190-196.

Prescott, D.M. 1994. The DNA of Cilaite Protozoa. Microbiol. Rev. 58:233-267.

Orias, E. 1991. Evolution of amitosis of the cilaite macronucleus: gain of the capcity to divide. J. Protozool. 38:217-221.

Rizzo, P.J. 1991. The enigma of the Dinoflagellate chromosome. J. Protozool. 38:1246-252.

Donelson, J.E. 1989. DNA rearrangements and antigenic variation in African trypanosomes. Chapter 35 In: Berg, D.E. & Howe, M.M., eds. Mobile DNA. ASM publications, Washington, DC. pp763-781.

Seiwert, S.D. & Stuart, K. 1994. RNA editing: transfer of genetic information from gRNA to precursor mRNA in Vitro. Science 266:114-117.

VanHamme, L. & E. Pays 1995. Control of gene expression in Trypanosomes. Microbiol. Rev. 59:223-240.