From Transcriptomes to Metatranscriptomes: Cold Adaptation and Active Metabolisms of Psychrophiles from Cold Environments
Transcriptomic and metatranscriptomic studies have yielded important insights into the mechanisms and metabolisms that allow psychrophiles to remain active in cold environments. Psychrophiles undergo numerous changes to their transcriptional profiles at colder temperatures and change the regulation of genes involved in most cellular processes, including primary metabolism and biosynthetic pathways, cell wall and peptidoglycan biosynthesis, lipid biosynthesis and cell membrane composition, translation/transcription/replication processes, protein turnover and chaperone functions, and stress responses. Increases in the expression of cold shock proteins, RNA/DNA helicases, protein chaperones, osmoprotectants, and proteins involved in the oxidative stress response are common features of cold adaptation in psychrophiles, as are changes to the cell membrane to increase fluidity and thickening of the cell wall. Metatranscriptome studies from permafrost and marine environments have begun to lay the groundwork for our understanding of the active metabolisms in these ecosystems and their potential impact on greater global processes such as biogeochemical cycles and greenhouse gas emissions. Community-specific microbial interactions, changes in temperature, degree of thaw, and nutrient, water, and organic matter availability, are all important drivers and regulators of microbial activity and metabolism, and changes in any of these factors can have significant impacts on microbial community function.
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