Many organisms in deep-sea environments are extremophiles thriving in extreme conditions: high pressure, high or low temperature, or high concentrations of inorganic compounds. This book presents the microbiology of extremophiles living in the deep sea and describes the isolation, cultivation, and taxonomic identification of microorganisms retrieved from the Mariana Trench, the world's deepest point. Also explained are techniques for recovering pressure-loving bacteria, the barophiles (piezophiles), and for whole genome analysis of Bacillus halodurans C-125. Physiological analysis of the pressure effect in Saccharomyces cerevisiae and Escherichia coli is used to answer the question of how deep-sea organisms survive under high hydrostatic pressure. These research results are useful in both basic science and industrial applications. Readers discover a new microbial world in the ocean depths, with state-of-the-science information on extremophiles.