lexen glacial image

LEXEN: Hitchhiking, a Mechanism for Bacterial Speciation in an Extremely Cold Environment


National Science Foundation

10/01/00 - 09/30/03

PI:  Wade H. Jeffrey

Bacteria are "hitchhikers" in glaciers; deposited from above on windborne dust particles and aerosols, overlayered by thousands of years of deposition and accretion, and finally returned to the coastal marine environment by glacial calving and melting. In the context of "glacial hitchhiking", this NSF-supported project aims to determine whether bacteria sustain significant levels of DNA base damage during glacial entrapment and if this base damage leads to mutations. In the absence of DNA replication and repair, the degradation of DNA may occur at a significant rate and base modifications resulting from spontaneous depurinations, depyrimidinations, and deaminations may accumulate. Even at temperatures considerably below 0EC a significant load of base alterations would occur in bacteria during the extended time in the glacier. Although much of the DNA degradation would be lethal to dividing bacteria, it is probable that organisms that are successful in recovering from the ice replicate their DNA using a template containing significant levels of base modifications; this would lead to a significant mutation frequency. From our work we will gain insight into basic mechanisms of mutagenesis that may be relevant to bacterial speciation, diversity and the evolution of life on earth as well as in extremely cold environments found elsewhere in our solar system. We also expect to show a correlation between DNA damage, cell lethality, and mutagenesis with respect to time spent in the glacier, thus providing a novel and facile approach for ice core dating.