Psychrobacter vallis sp. nov. and Psychrobacter aquaticus sp. nov., from Antarctica

Twelve strains of psychrophilic bacteria were isolated from cyanobacterial mat samples collected from various water bodies in the McMurdo Dry Valley region of Antarctica. All the isolates were Gram-negative, non-motile, coccoid, psychrophilic, halotolerant bacteria and had C16:1ω7c, C17:1ω8c and C18:1ω9c as the major fatty acids, ubiquinone-8 as the respiratory quinone and DNA G+C content of 41-46 mol%. Based on these characteristics, the isolates were assigned to the genus Psychrobacter. Based on their SDS-PAGE profiles, the 12 isolates could be categorized into three groups. Six isolates of Group I were identified as representing strains of Psychrobacter okhotskensis. However, using detailed phenotypic and chemotaxonomic characteristics and phylogenetic analysis based on their 16S rRNA gene sequences, strain CMS 39T, the only strain from Group II, and strain CMS 56T, a representative strain of Group III, were different from each other and from all recognized species of Psychrobacter. Therefore, it is proposed to classify CMS 39T (=DSM 15337T=MTCC 4208T) and CMS 56T (=DSM 15339T=MTCC 4386T) as representing the type strains of novel species of Psychrobacter, for which the names Psychrobacter vallis sp. nov. and Psychrobacter aquaticus sp. nov., respectively, are proposed