Bacteria in Glaciers: A Mechanism for Bacterial Speciation in an Extremely Cold Environment

University Of Texas, M.D. Anderson Cancer Center, Houston TX

Investigators

Abstract

The presence of bacteria in glaciers has generated considerable public and scientific interest in recent times. Bacteria are deposited from above on wind-borne 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. Bacteria have been detected in and cultured from glacial ice ranging from a few hundred to many thousands of years old. Evidence suggests that glacial ice cannot support bacterial growth but rather traps these organisms for considerable lengths of time in an anabolic state. This research will test the hypothesis that bacteria sustain significant levels of DNA degradation and damage (base damage) during glacial entrapment and that this base damage leads to mutations. Ice core samples representing a wide range of geographical locales and age distributions will be obtained from the National Ice core Laboratory (NICL). Current and emerging molecular biology tools will be used to analyze bacteria and bacterial DNA extracted from these ice cores. A diverse array of bacteria extracted from glacial ice will be cultured, preserved, and characterized. A recently developed technology to detect and quantify base loss and deaminations in single bacterial cells using damage-specific endonucleases and visualization of double-strand breaks using microgel electrophoresis will be employed. The lethal effects of glaciation on bacteria using clonability, transcription, protein synthesis, and fluorescence hybridization using rRNA probes as biological endpoints will be examined. Relative mutation frequencies in bacterial isolates will also be estimated by comparing sequence homologies within conserved and nonconserved regions of the 16S rDNA genes. From the proposed work, insight will be gained into understanding 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.