Characterization of several Psychrobacter strains isolated from Antarctic environments and description of Psychrobacter luti sp. nov. and Psychrobacter fozii sp. nov.

Eleven psychrophilic bacteria isolated from Antarctic coastal marine environments were subjected to a polyphasic taxonomic study. The isolates were oxidase-positive, halotolerant, gram-negative, non-motile coccobacilli with a strictly oxidative metabolism. The DNA G + C content ranged from 44 to 47 mol%. DNA-DNA hybridization experiments showed six homology groups, two of them related at the species level to the type strain of Psychrobacter immobilis, LMG 7203T (70-83%). The highest DNA relatedness of two other groups to known Psychrobacter species was found to the type strain of Psychrobacter glacincola, LMG 21282T (51-57%), and no significant similarity was found between Psychrobacter type strains and the last two groups. The predominant cellular fatty acids detected were typical of the genus Psychrobacter and included 18:1omega9c, 16:1omega7c and 17:1omega8c. 16S rRNA gene sequence analysis confirmed that the strains isolated belonged to the genus Psychrobacter. The results of the study assigned five isolates to P. immobilis, three isolates to P. glacincola and three isolates to novel Psychrobacter species. The names Psychrobacter luti sp. nov. (type strain NF11T=LMG 21276T=CECT 5885T) and Psychrobacter fozii sp. nov. (type strain NF23T=LMG 21280T=CECT 5889T) are proposed for these organisms.

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. 16S 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 19866T) is proposed for the third organism.