Shewanella frigidimarina and Shewanella livingstonensis sp nov isolated from Antarctic coastal areas

Three strains of psychrophilic bacteria isolated from Antarctic coastal marine environments were studied to determine their taxonomic position. These bacteria were Gram-negative rods, facultatively anaerobic and motile by means of a single polar flagellum. None of the bacterial isolates had an Na+ requirement. Only one of the strains was capable of producing H2S from thiosulfate. The DNA base content of these bacteria was 41-42 mol% G+C. DNA-DNA hybridization experiments showed that the isolates formed two related groups that exhibited about 70 and 24% DNA-DNA homology, respectively, with the type strain of Shewanella frigidimarina. The fatty acid profiles of the bacterial isolates were similar to the profiles of other Shewanella species. All the strains contained both ubiquinones and menaquinones, like Shewanella species. Methylmenaquinones were also found. 165 rRNA gene analysis confirmed that isolated strains belonged to the genus Shewanella and were phylogenetically related to the newly identified Shewanella frigidimarina. The results of the polyphasic taxonomic study assigned the three isolates to Shewanella and two of them specifically to Shewanella frigidimarina. The name Shewanella livingstonensis sp. nov. (type strain LMG 19866(T)) is proposed for the third organism.