Halomonas titanicae sp. nov., a halophilic bacterium isolated from the RMS Titanic

Abstract

A Gram-negative, heterotrophic, aerobic, non-endospore-forming, peritrichously flagellated and motile bacterial strain, designated BH1T, was isolated from samples of rusticles, which are formed in part by a consortium of micro-organisms, collected from the RMS Titanic wreck site. The strain grew optimally at 30–37 °C, pH 7.0–7.5 and in the presence of 2–8 % (w/v) NaCl. We carried out a polyphasic taxonomic study in order to characterize the strain in detail. Phylogenetic analyses based on 16S rRNA gene sequence comparison indicated that strain BH1T clustered within the branch consisting of species of Halomonas. The most closely related type strains were Halomonas neptunia (98.6 % 16S rRNA sequence similarity), Halomonas variabilis (98.4 %), Halomonas boliviensis (98.3 %) and Halomonas sulfidaeris (97.5 %). Other closely related species were Halomonas alkaliphila (96.5 % sequence similarity), Halomonas hydrothermalis (96.3 %), Halomonas gomseomensis (96.3 %), Halomonas venusta (96.3 %) and Halomonas meridiana (96.2 %). The major fatty acids of strain BH1T were C18 : 1 ω7c (36.3 %), C16 : 0 (18.4 %) and C19 : 0 cyclo ω8c (17.9 %). The DNA G+C content was 60.0 mol% (T m). Ubiquinone 9 (Q-9) was the major lipoquinone. The phenotypic features, fatty acid profile and DNA G+C content further supported the placement of strain BH1T in the genus Halomonas. DNA–DNA hybridization values between strain BH1T and H. neptunia CECT 5815T, H. variabilis DSM 3051T, H. boliviensis DSM 15516T and H. sulfidaeris CECT 5817T were 19, 17, 30 and 29 %, respectively, supporting the differential taxonomic status of BH1T. On the basis of the phenotypic, chemotaxonomic and phylogenetic data, strain BH1T is considered to represent a novel species, for which the name Halomonas titanicae sp. nov. is proposed. The type strain is BH1T (=ATCC BAA-1257T =CECT 7585T =JCM 16411T =LMG 25388T).