Isolation of a gene regulated by hydrostatic pressure in a deep-sea bacterium

Barophilic bacteria inhabit the deep oceans, and the specific functional modifications and regulatory mechanisms which govern adaptation to hydrostatic pressure are beginning to be understood. For example, the rate of production of several proteins by some hydrothermal vent archaebacteria and the degree of saturation of membrane lipids in other deep-sea bacteria have been found to change as a result of cultivation at high pressure. We report here the cloning of gene, ompH, which encodes a major pressure-inducible protein of strain SS9, a gram-negative eubacterium isolated from a depth of 2.5 kilometres in the Sulu Sea. Messenger RNA encoded by ompH is expressed when cells are grown at 280 atm but not at 1 atm, indicating that transcription of the ompH gene is controlled by hydrostatic pressure. The function of the OmpH protein in adaptation to high pressure and the use of the ompH gene in studying how bacteria sense and respond to pressure is discussed.