Microbial adaptation to high pressure

Piezomicrobiology is one of the lesser studied areas in extremophilic microbiology, although it constitutes a significant field of research, considering that piezophilic microorganisms reside in the largest habitat on Earth—the deep sea. High-pressure microbial habitats include the abyssal and hadal deep-sea environments, which are typified by low temperatures, darkness, sporadic nutrient inputs, and high diversity (low biomass) of invertebrate and vertebrate life. The abyssal plain is commonly thought of as a barren desert, punctuated by the presence of reducing environments such as hydrothermal vents, cold seeps, and whale falls. Culture-independent analyses of microbial diversity in low-temperature deep-ocean habitats have indicated the presence of particular groups of Eukarya, Archaea, and Bacteria. One of the classic responses of mesophilic microbial cells to growth-permissive elevated pressure is the impairment of cell division. The SOS regulon includes genes whose products repair DNA damage as well as prevent cell division. In order to gain further insight into the nature of elevated pressure as a stress, the response of Escherichia coli to pressure has been examined. Many DNA-binding proteins display pressure-sensitive binding properties, and in many instances, this is due to hydration effects. Translation is another pressure-sensitive cellular process involving nucleic acid-protein interactions. Among the ribosome structures present throughout the elongation cycle the most pressure-sensitive one appears to be the posttranslocational complex. The description of genes required for high-pressure growth is now remarkably small but is likely to be greatly expanded as a result of ongoing genetic and genomic studies.