Sequence of the ompH gene from the deep-sea bacterium Photobacterium SS9.

In contrast to studies of many other extremophiles, the molecular characterization of the barophilic or high-pressure-adapted bacteria of the deep ocean is virtually nonexistent. One exception is the discovery that the moderate barophile Photobacterium SS9 preferentially synthesizes a 37-kDa outer membrane protein, designated OmpH, in response to elevated hydrostatic pressure. We report here on the molecular characterization of the ompH gene. The deduced amino acid sequence of mature OmpH is similar to a number of porin proteins, including significant similarity to porin protein P2 from Haemophilus influenzae. It appears likely that OmpH is a unique porin whose synthesis is responsive to changes in the pressure regime of the deep-sea bacterium.