Fatty Acid Regulation in a Deep-Sea Bacterium

本研究的目的是鉴定和表征深海细菌光杆菌种菌株SS9中参与压力传感和高压适应的基因。遗传学研究表明，多不饱和脂肪酸种类全顺式5、8、11、14、17-二十碳五烯酸（EPA）的丰度、高压适应和外膜蛋白（OMP）基因表达的压力调节之间存在联系。本研究旨在确定SS9的高压适应是否需要EPA，并区分两种监管可能性；首先，最可能通过对膜物理状态的影响，EPA影响压力感应和omp基因的调节，或者第二，一个共同的全局调节因子控制编码压力可调节omp和影响EPA丰度的基因的表达。将在现有的SS9突变株EC1002中鉴定导致omp基因表达降低、EPA丰度降低和高压生长能力降低的突变，并阐明菌株EC1002假回复性高压适应的遗传基础。其他突变体缺乏合成不饱和脂肪酸（UFAs）将获得和表征。UFAs在高压生长和压力调节基因表达中的作用将得到阐明。将研究高压或低温对UFA基因调控的可能性。最后，将测量所有SS9 UFA突变体和菌株EC1002耐高压衍生物制备的脂质分散体的膜流动性。机械感受是所有生物体中一种常见的感觉方式。这些实验将深入了解脂肪酸在细胞对机械刺激的反应中可能发挥的作用。它们还将提供基因和生化适应方面的信息，这些信息使深海环境中的生命成为可能。最后，该项目将导致分离与EPA生物合成有关的基因，这可能以后为利用重组DNA技术过量生产用于生物技术的EPA提供手段。对EPA的短期需求是作为水产养殖和家禽养殖的食品补充。从长期来看，EPA是人类需要的一种膳食补充剂在这种情况下，它对人类营养非常重要。＊＊＊

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. ***