Physiology and Biochemistry of Methanocaldococcus jannaschii at Elevated Pressures

Methanocaldococcus jannaschii was originally isolated from the vicinity of a hydrothermal vent at a depth of 2,600 m, making it an ideal candidate for studies of pressure effects on the physiology of a deep-sea archaeon. This chapter summarizes the effects of pressure on selected proteins, lipids, and gene expression levels of M. jannaschii, one of the few known hyperthermophilic piezophiles, and presents a few prospects for future research. Methane has been used to measure growth rates of M. jannaschii at elevated pressures. Pressure effects on protein folding and reaction rates are based on Le Chatelier’s principle. Although it is difficult to generalize, some trends have emerged from recent studies of pressure effects on protein stability, at least below 200 MPa. Archaeal lipids consist primarily of isoprenoid hydrocarbons and alkylglycerol ether-derived polar lipids not found in bacteria or eukaryotes. The chapter has summarized how pressure affects the growth, membrane composition, and gene expression profiles of M. jannaschii, as well as pressure effects on the activity and stability of several of the organism’s key enzymes. These studies have thus expanded our understanding of how pressure affects the biochemistry and physiology of a hyperthermophilic piezophile. One strategy for addressing this question is to examine pressure effects on the activity of transcriptional regulators. For example, piezotolerant host strains might be generated with the aim of using pressure as an operational variable to regulate recombinant protein production.