Life in the cold biosphere: The ecology of psychrophile communities, genomes, and genes

Abstract

The prevalence of low temperature habitats on Earth makes the ecology of organisms adapted to low temperature environments (psychrophiles) an important area of research. Studies of low temperature ecosystems including the deep sea, sea ice, glacial ice, permafrost, and snow have provided a wealth of knowledge on the resilience of psychrophilic microbial ecosystems in the face of anthropogenic and natural disturbance, the history of microbial life on Earth, and the potential distribution of life in extraterrestrial environments. Taking these three knowledge areas as motivation, this dissertation further explores psychrophile ecology. Chapter 1 introduces the history of research on psychrophiles. Chapters 2 and 3 explore the diversity of Bacteria found in two understudied psychrophile habitats; multiyear sea ice and frost flowers. Chapter 4 explores the metabolic potential of the latter environment through metagenomics. Chapter 5 introduces a novel method for evaluating genome plasticity in populations, and applies this method in a comparative analysis of psychrophiles and mesophiles. Chapter 6 examines how psychrophilic enzymes are optimized for low temperatures through amino acid substitutions and introduces a model for further exploration of amino acid preferences. Chapter 7 explores the potential for psychrophiles to degrade alkanes, a major component of crude oil, by the presence of genes coding for alkane hydroxylases.