Halomonas stenophila sp. nov., a halophilic bacterium that produces sulphate exopolysaccharides with biological activity.

We have undertaken a polyphasic taxonomic study of two halophilic, Gram-negative bacterial strains, N12(T) and B-100, that produce sulphated exopolysaccharides with biological activity. They were isolated from two different saline soil samples. Both strains grow at NaCl concentrations within the range 3-15 % (w/v) [optimum 5-10 % (w/v)], at 15-37 °C (optimum 20-32 °C) and at pH 6-8 (optimum pH 7-8). Their 16S rRNA gene sequences indicate that they belong to the genus Halomonas in the class Gammaproteobacteria. Their closest relative is Halomonas nitroreducens, to which our strains show maximum 16S rRNA gene sequence similarity values of 98.7 % (N12(T)) and 98.3 % (B-100). Their DNA G+C contents are 61.9 and 63.8 mol%, respectively. The results of DNA-DNA hybridizations showed 43.9 % relatedness between strain N12(T) and H. nitroreducens CECT 7281(T), 30.5 % between N12(T) and Halomonas ventosae CECT 5797(T), 39.2 % between N12(T) and Halomonas fontilapidosi CECT 7341(T), 46.3 % between N12(T) and Halomonas maura CECT 5298(T), 52.9 % between N12(T) and Halomonas saccharevitans LMG 23976(T), 51.3 % between N12(T) and Halomonas koreensis JCM 12237(T) and 100 % between strains N12(T) and B-100. The major fatty acids of strain N12(T) are C(12 : 0) 3-OH (5.42 %), C(15 : 0) iso 2-OH/C(16 : 1)ω7c (17.37 %), C(16 : 0) (21.62 %) and C(18 : 1)ω7c (49.19 %). The proposed name for the novel species is Halomonas stenophila sp. nov. Strain N12(T) ( = CECT 7744(T)  = LMG 25812(T)) is the type strain.