Abstract
Two novel psychrophilic, halophilic, Psychrobacter-like bacteria, strains KMM 225(T) and KMM 277(T), were isolated from sea water and the internal tissues of an ascidian Polysyncraton sp. specimen, respectively, and characterized using a polyphasic approach, which included phenotypic, genotypic, chemotaxonomic and phylogenetic analyses. The novel marine isolates were Gram-negative, aerobic, coccoid, oxidase- and catalase-positive, non-pigmented, non-motile, psychrophilic and halophilic and they utilized a restricted spectrum of carbon sources. Strains KMM 225(T) and KMM 277(T) required sea water or sodium ions for growth and were tolerant of up to 12--15% (w/v) NaCl. Growth of strains KMM 225(T) and KMM 277(T) was observed at 4--35 and 7--35 degrees C, respectively. The DNA G+C contents of KMM 225(T) and KMM 277(T) were respectively 46.8 and 50.7 mol%. Comparison of almost complete 16S rDNA sequences of strains KMM 225(T) and KMM 277(T) revealed that both strains were phylogenetically most closely related to each other (99.9% sequence similarity) and slightly less related to Psychrobacter glacincola, with 97.2 and 97.8% similarity, respectively. DNA--DNA reassociation between KMM 225(T) and KMM 277(T) revealed 15% similarity, whereas similarity to other Psychrobacter species was 14--25%. Strains KMM 225(T) and KMM 277(T) differed from one another in their growth temperature, organic substrate utilization, antibiotic sensitivity and DNA G+C content. Both strains examined could be distinguished from all previously described Psychrobacter species by their physiological, genotypic and phylogenetic characteristics. On the basis of the physiological and molecular properties of the novel isolates, the names Psychrobacter submarinus sp. nov. (type strain KMM 225(T)=DSM 14161(T)) and Psychrobacter marincola sp. nov. (type strain KMM 277(T)=DSM 14160(T)) are proposed.