Fatty Acid Regulation in a Deep-Sea Bacterium

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9630546 Bartlett The objective of this investigation is to identify and characterize genes involved in pressure sensing and high pressure adaptation in the deep-sea bacterium Photobacterum species strain SS9. Genetic studies in this organism indicate that a link exists between the abundance of the polyunsaturated fatty acid species all-cis-5, 8, 11, 14, 17-eicosapentaenoic acid (EPA), high pressure adaptation, and the pressure regulation of outer membrane protein (OMP) gene expression. This research seeks to establish whether EPA is required for high pressure adaptation in SS9 and to distinguish between 2 regulatory possibilities; first that EPA, most likely through effects on the physical state of the membrane, influences pressure-sensing and omp gene regulation, or second, that a common global regulatory factor controls the expression of genes encoding pressure-regulatable OMPs and those which influence EPA abundance. The mutation responsible for decreased omp gene expression, EPA abundance, and high pressure growth ability will be characterized in the existing SS9 mutant strain EC1002, and the genetic basis for high pressure adaption in pseudorevertants of strain EC1002 will also be elucidated. Additional mutants deficient in the synthesis of unsaturated fatty acids (UFAs) will be obtained and characterized. The role of UFAs in high pressure growth and pressure-regulated gene expression will be clarified. Possible UFA gene regulation by high pressure or cold temperature will be investigated. Finally, the membrane fluidity of lipid dispersions prepared form all SS9 UFA mutants and high pressure resistant derivatives of strain EC1002 will be measured. %%% Mechanoreception is a common sensory modality in all organisms. These experiments will provide insight into the possible role played by fatty acids in signalling a cellular response to a mechanical stimulus. They will also provide information into genetic and biochemical adaptations which make life possible in deep-sea e nvironments. Finally, the project will result in the isolation of genes involved in EPA biosynthesis which could later provide the means for using recombinant DNA technologies to overproduce EPA for biotechnology. The short term need for EPA is as a food supplement in aquaculture and poultry farming. In the longer term EPA is needed as a dietary supplement for humans in which case it has been shown to be of major importance in human nutrition. ***