The deep biosphere exists in an environment dominated by high hydrostatic and lithostatic pressure. In most studies of subsurface microbiology, however, pressure is not considered, and methods commonly used may select for organisms that tolerate atmospheric pressure conditions. During the course of my C-DEBI Postdoctoral Fellowship, I undertook a series of experiments aimed at understanding the importance of pressure in studies of the subsurface biosphere. First, I made attempts at reviving dormant piezophiles from previously-stored samples to test whether pressure could select for organisms native to the deep biosphere against contaminants that may have arisen during storage. Second, I extracted DNA and analyzed 16S Tag sequences from samples collected at the mid-Cayman Spreading Center, with comparisons between freshly-collected samples and samples which had been stored for one year under either atmospheric or in situ pressure conditions, to analyze how populations change during sample storage. Sequence analysis is currently underway for this project. Third, I conducted experiments on the effect of pressure on metabolic rates using samples or organisms from high-pressure environments. These experiments showed evidence of pressure dependence, though the effect differs between metabolic processes. Through these several studies, I have found that the effect of pressure on deep biosphere communities is something that should not be ignored, especially in studies where metabolic activity rates are measured.