Key words: Extremophiles, origins of life, adaptation, astrobiology

My keen curiosity for extremophiles began with a course taught by Dr. Thomas Bobik titled Prokaryotic Diversity and Ecology, where I was introduced to a plethora of distinctive metabolic, phylogenetic, and adaptive features of various single-celled organisms. The graduate cross-listed course material examined the mechanisms of which prokaryotes use to overcome the inconceivable challenges of microbial life. 

As a final presentation, I taught two dozen students about the arctic permafrost bacterium, Planococcus halocryophilus. This cryoenvironment extremophile of Arctic ice is characterized as both halophilic and psychrophilic; thriving in an environment of high salinity (up to 18% NaCl) and extremely low temperature (-15°C). I examined the genotypic and resulting phenotypic adaptation features of P. halocryophilus to survive in this environment primarily through a 2013 study by N. Mykytczuk et. al. According to their research of over 200 Canadian high arctic isolates screened, the known cryophilic bacteria were also halophilic, indicating subzero growth coincides with osmotolerance. 

I continued to research related adaptations that permit the organism to reside and reproduce, overcoming barriers such as: decreased membrane fluidity, slowed transcription and denaturation rates, and the increased risk of intracellular ice formation. A key finding within the sequenced genome was a significant redundancy of genes— approximately 17%— that expressed cold and osmotic-specific adaptive mechanisms. These genes have been associated with increased fitness through selective upregulation, altered amino acid distribution, and solute binding. The high genomic redundancy assures a buffer for mutations among the decreased translation efficiency, and the continued production of ice-binding proteins to regulate internal crystallization. 

This investigation into the Mykytczuk study on P. halocyophilus forms a foundation for my prospective doctoral studies of understanding the genetic components attributed to organismal survival. My interest in the origins and survivability of lifeforms has only progressed since, by pondering the limits of life, breadth of adaptability, and seeing the impact this knowledge can have on humanity.