How Microbes Can Survive Eons of Freezing Conditions

Most microbial researchers grow their cells in petri dishes to study how they respond to stress and damaging conditions. But, with the support of funding from NASA, researchers in Louisiana State University’s (LSU’s) Department of Biological Sciences tried something almost unheard of: studying microbial survival in ice to understand how microorganisms could survive in ancient permafrost, or perhaps even buried in ice on Mars. Dr. Brent Christner, associate professor of biological sciences, and colleagues at LSU including postdoctoral researcher Dr. Markus Dieser and Mary Lou Applewhite Professor John Battista, had results on DNA repair in ice-entrapped microbes published online on September 27, 2013 by the journal Applied and Environmental Microbiology. To understand how microbes survive in frozen conditions, Christner and colleagues focused on analysis of DNA, the hereditary molecule that encodes the genetic instructions used in the development and function of all organisms. “Microbes are made up of macromolecules that, even if frozen, are subject to decay,” Dr. Christner said. “We know of a range of spontaneous reactions that result in damage to DNA.” The worst kind of damage is known as a double-stranded break, where the microbe’s DNA is cleaved into two separate pieces that need to be put back together to make the chromosome functional. “This kind of damage is inevitable if cells exist frozen in permafrost for thousands of years and cannot make repairs,” Dr. Christner said. “Imagine that a microbe is in ice for extended periods of time and its DNA is progressively getting cut into pieces. There will eventually be a point when the microbe’s DNA becomes so damaged that it’s no longer a viable informational storage molecule. What is left is a corpse.” The situation would seem dire for the longevity of microbes in ice.
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