High-Pressure Biochemistry and Biophysics

By the end of the 19th century British and French oceanographic expeditions had shown that life exists in the deepest ocean trenches. Since then, microorganisms have been found to thrive in diverse environments characterized by a wide range of pressure-temperature-composition (P-T-X) conditions (Rothschild and Mancinelli 2001). The range of physicochemical conditions under which microbial life has been observed has continued to expand with greater access to extreme environments and greatly improved tools for sampling and assessing the diversity and physiology of microbial communities. This exploration now includes examination of subseafloor and continental subsurface settings—key goals of the Deep Life Directorate within the Deep Carbon Observatory (DCO) Program. Bacterial metabolic activity has been described at temperatures as low as −40 °C (Rivkina et al. 2000; Price and Sowers 2004; Panikov and Sizova 2007; Collins et al. 2010) and a methanogen has been cultured at 122 °C under hydrostatic pressure (Takai et al. 2008). Moreover, bacteria can withstand ionizing radiation levels up to 30,000 grays (Rainey et al. 2005), and can grow over a pH range between 0 and 12.5 (Takai et al. 2001; Sharma et al. 2012), at salinities up to 5.2 M NaCl (Kamekura 1998), and at hydrostatic pressures up to 130 MPa (Yayanos 1986). Bacterial survival has also been demonstrated up into the GPa range (Sharma et al. 2002; Vanlint et al. 2011).