Genomic Insight into the Salt Tolerance of Enterococcus faecium, Enterococcus faecalis and Tetragenococcus halophilus

To shed light on the genetic basis of salt tolerance in Enterococcus faecium, Enterococcus faecalis, and Tetragenococcus halophilus, we performed comparative genome analysis of 10 E. faecalis, 11 E. faecium, and three T. halophilus strains. Factors involved in salt tolerance that could be used to distinguish the species were identified. Overall, T. halophilus contained a greater number of potassium transport and osmoprotectant synthesis genes compared with the other two species. In particular, our findings suggested that T. halophilus may be the only one among the three species capable of synthesizing glycine betaine from choline, cardiolipin from glycerol and proline from citrate. These molecules are well-known osmoprotectants; thus, we propose that these genes confer the salt-tolerance of T. halophilus.