Description of a Sulfitobacter Strain and Its Extracellular Cyclodipeptides

A marine bacterium M44 was separated from 30m deep seawater in the East China Sea (26 degrees 28.3' N 122 degrees 29.0' E) in 2006. 16S rDNA gene sequence comparison showed that the strain M44 was a member of the genus Sulfitobacter and highly similar to KMM 35547(T). A series of experiments demonstrated that this strain M44 had many distinctive characteristics: its cells were gram-negative and mesophilic; its colonies were slightly yellowish, round, convex, and smooth; and it could grow at 10-28 degrees C, pH 6.0-10.0, and in the presence of 0-12.5% (w/v) NaCl; the optimum growth conditions were 25. C and pH 7.0, and the optimum Na+ concentration was 2.5%. In addition, strain M44 contained 18 : 1 omega 7c, 11methyl 18 : 1 omega 7c and 16 : 0 fatty acids as major fatty acids, and the genomic DNA G+C content was 58.04 mol%. According to our results of the secondary metabolites, six cyclodipeptides were isolated from the strain M44, which were Cyclo (Val-Leu), Cyclo (Phe-Val), Cyclo (Phe-Leu), Cyclo (Leu-Ile), Cyclo (Phe-Ile), and Cyclo (Trp-Pro). It is the first study of secondary metabolites isolated from this genus.