Halophlies can be loosely classified as slightly, moderately or extremely halophilic, depending on their requirement for NaCl. The extremely halophilic archaea, in particular, are well adabted to saturating NaCl concentrations and have a number of novel molecular characteristics, such as enzymes that function in saturated salts, purple membrane that allows phototrophic growth, sensory rhodopsins that mediate the phototatics response, and gas vesicles that promote cell flotation. Halophlies are found distributed all over the would in hypersaline environments, many in natural hypersaline brine in arid, coastal, and even deep-sea locations, as well as artificial salterns used to mine salts from the sea. Their novel characteristics and capacity for large-scale culturing make halophiles protentially valuable for biotechnology.