Metabolic response of Tetragenococcus halophilus under salt stress

In this study, the effect of salt stress on metabolic response of Tetragenecoccus halophilus was investigated, and the metabolic alternations were analyzed using liquid chromatography-mass spectrometry according to the metabolomics approach. A total of 81 intracellular metabolites were identified, and significant differences were observed in the levels of metabolites mainly participating in central carbon metabolism, fatty acid metabolism, and amino acid metabolism. Analysis of the membrane fatty acid distribution showed that higher proportions of unsaturated fatty acid were observed in salt-treated cells. Additionally, salt-stressed cells exhibited higher amounts of compatible solutes including proline, glycine, citrulline, and N-acetyltyrptophan, and lower amounts of branched-chain amino acids. Interestingly, higher amounts of indole, salicylic acid, and coronatine, which are regarded as signaling molecule and suggested to combat osmotic stress, were detected in salt-shocked cells compared with the untreated cells. Taken together, these results suggested that increased unsaturated membrane fatty acids, accumulation of compatible solutes, and up-regulation of signaling molecule may be potential mechanisms employed by T. halophilus during salt stress.