Effect of fabA and desA Mediated Low Temperature Adaption on Shewanella putrefaciens via Regulation of Unsaturated Fatty Acid Metabolism

Shewanella putrefaciensis a kind of spoilage bacteria in low temperature chilled aquatic products, which seriously threats human health and aquaculture. The fatty acid composition of S. putrefaciens cell membranes has been shown to be involved in adaption of bacteria to various environments. However, the specific fatty acid metabolism of S. putrefaciens to the low temperature environment remains unknown. In this study, the growth of S. putrefaciens, the response of fatty acid composition to low temperature production, and the differential expression and synthesis of enzymes related to unsaturated fatty acid synthesis were investigated by lack of fabA and desA in S. putrefaciens. Results showed that loss of fabA and desA suppressed the growth of S. putrefaciens and reduced unsaturated fatty acid contents at low temperature. In addition, the upregulation of fabA, but not desA resulted in accumulation of unsaturated fatty acid. Up-regulations of fabA and desA both resulted in promotion of GPR41 and Retn gene and protein expressions. These results demonstrated that the deletions of fabA and desA resulted in reduction of unsaturated fatty acid and key downstream genes of fatty acid metabolism, which suggested that unsaturated fatty acid was involved in the adaptations of fabA and desA-mediated S. putrefaciens to the low temperature environment. These results provided a tentative mechanism of the synthesis of unsaturated fatty acids in S. putrefaciens under low temperature conditions.