Halomonas rituensis sp. nov. and Halomonas zhuhanensis sp. nov., isolated from natural salt marsh sediment on the Tibetan Plateau

Abstract

Two novel Gram-stain-negative, aerobic and non-motile rods bacteria, designated TQ8ST and ZH2ST, were isolated from salt marsh sediment collected from the Tibetan Plateau. Strain TQ8ST was found to grow at 10–40 °C (optimum, 30 °C), pH 6.0–11.0 (optimum, pH 8.0–9.0) and in the presence of 2–12 % (w/v) NaCl (optimum, 6–8 %). Strain ZH2ST was found to grow at 15–40 °C (optimum, 30 °C), pH 7.0–10.0 (optimum pH 9.0) and in the presence of 2–10 % (w/v) NaCl (optimum, 4–6 %). Phylogenetic analysis based on the 16S rRNA gene sequences showed that strains TQ8ST and ZH2ST shared 99.07 % sequence similarity between each other and were affiliated with the genus Halomonas , sharing 97.48 % and 97.41 % of sequence similarity to their closest neighbour Halomonas sulfidaeris Esulfide1T, respectively. DNA–DNA hybridization analyses showed 61.0 % relatedness between strains TQ8ST and ZH2ST. The average nucleotide identity and the average amino acid identity values between the two genomes were 92.33 and 92.84 %, respectively. The values between the two strains and their close phylogenetic relatives were all below 95 %. The major respiratory quinones of strain TQ8ST were Q-9 and Q-8, while that of ZH2ST was Q-9. The main fatty acids shared by the two strains were C18 : 1  ω6c and/or C18 : 1  ω7c, C16 : 1  ω6c and/or C16 : 1  ω7c, C16 : 0 and C12 : 0 3-OH. Strain ZH2ST can be distinguished from TQ8ST by a higher proportion of C19 : 0 cyclo ω8c. The G+C content of the genomic DNA of strains TQ8ST and ZH2ST were 57.20 and 57.14 mol%, respectively. On the basis of phenotypic distinctiveness and phylogenetic divergence, the two isolates are considered to represent two novel species of the genus Halomonas , for which the names Halomonas rituensis sp. nov (type strain TQ8ST=KCTC 62530T=CICC 24572T) and Halomonas zhuhanensis sp. nov (type strain ZH2ST=KCTC 62531T=CICC 24505T) are proposed.