Salinity and the Regulation of Membrane Lipids in the Marine Bacterium Moritella marina MP-1: Implications in Cellular Bioenergetics and Potential Roles in the Marine Food Web

Docosahexaenoic acid (DHA, 22:6n3) is an omega-3 polyunsaturated fatty acid comprised of 22 carbons and 6 methylene interrupted double bonds beginning at carbon three relative to the methyl carbon. DHA is enriched in the membranes of mitochondria, neurons, sperm, and some deep-sea bacteria. In humans DHA content has been associated epidemiologically with a reduced risk of certain health conditions such as cardiovascular disease, Alzheimer's, and multiple sclerosis. The food and agricultural sciences have responded to these compositional associations with efforts to produce more omega-3 fatty acids as part of the food supply. Despite increasing interest in the health benefits of DHA, the precise mechanisms by which DHA provides health benefits remain unknown.;Previous reports suggest the unique structure and molecular dynamics of DHA provide physical properties and facilitate membrane functions that are distinctive from both monounsaturated and saturated fatty acids. Recently, the functions of DHA in the membranes of deep-sea bacteria have been examined for its molecular functions, indications of the evolutionary advantages DHA provides, and applications in biotechnology.;Here, work is presented which aims to illuminate and clarify the role of DHA in biological membranes by systematically studying the implications of maintaining membrane gradients important in cellular bioenergetics. The interplay between the membrane lipid composition of the DHA-producing deep-sea bacterium Moritella marina and salinity is examined, and a relationship between salinity and membrane phospholipid and fatty acid composition is demonstrated. In addition, the composition of phospholipid molecular species present in Moritella marina is elucidated. A role for DHA and other omega-3 polyunsaturated fatty acid producing bacteria in the marine food web is proposed, and applications for omega-3 polyunsaturated fatty acid production by marine bacteria are examined for use in the biotechnology, food, and agricultural sciences.