Halomonas nitroreducens sp. nov., a novel nitrate- and nitrite-reducing species

We have carried out a polyphasic taxonomic study of strain 11ST, a halophilic, Gram-negative bacterium that is able to respire on nitrate and nitrite in anaerobiosis. Strain 11ST was isolated from a solar saltern in Cahuil, a region next to Pichilemu (Chile). It grows at NaCl concentrations within the range of 3-20 % w/v (optimum 5-7.5 %), temperatures from 4 to 45 degrees C (optimum 20-32 degrees C) and within a pH range of 5-10 (optimum pH 7-9). Its 16S rRNA gene sequence indicates that it belongs to the genus Halomonas in the class Gammaproteobacteria. Its closest relatives are Halomonas alimentaria, H. denitrificans, H. organivorans and H. ventosae, with the type strains of which our strain showed maximum 16S rRNA gene sequence similarity values of 97.1-98.1 %. Its G+C content is 65.3 mol%. DNA-DNA hybridization studies showed 54.2 % relatedness between strain 11ST and H. alimentaria DSM 15356T and 47.2 % relatedness between strain 11ST and H. organivorans CECT 5995T. Lower DNA-DNA hybridization percentages were obtained against the type strains of other related Halomonas species. Its major fatty acids are C12 : 0 3-OH (5.56 %), iso-C15 : 0 2-OH/C16 : 1 omega 7c (22.30 %), C16 : 0 (27.80 %) and C18 : 1 omega 7c (29.92 %). The proposed name for the novel species is Halomonas nitroreducens sp. nov., with strain 11ST (=CECT 7281T =LMG 24185T) being the type strain.