Life in the bulk of the deep ocean occupies a relatively constant temperature but variable pressure environment. Such organisms possess unique biochemical and physiological adaptations for changes in pressure. We propose to examine pressure regulation of outer membrane protein synthesis in the deep-sea bacterium Photobacterium 559. Cultivating this organism from lower to higher pressures leads to the progressive induction of the OmpL, OmpH, and OmpI proteins. Pressure sensitive mutants impaired in the regulation of these proteins have already been isolated. We will characterize the previously cloned Omp regulatory locus and isolate additional regulatory loci which control omp gene expression. The deduced sequences of regulatory proteins will be examined for similarity to other proteins of known function, followed by regulatory protein localization in SS9, and sensory transduction analysis. We will also analyze regulatory mutants with regard to growth, Omp synthesis, and nutrient permeation and transport as a function of pressure. The deduced primary structures of the OmpL and OmpI proteins will also be obtained and the phenotypes of cells containing various combinations of ompL, ompH, and ompI mutations will be assessed. Mutants impaired in the synthesis of cAMP or the cAMP receptor protein (CRP) will be obtained in order to determine the role of the CRP-cAMP regulon in pressure adaptation and omp gene control. Finally, we will isolate and characterize suppressor mutations which restore high pressure growth to pressure sensitive omp regulatory mutants.
