Psychrobacter glacincola sp. nov., a halotolerant, psychrophilic bacterium isolated from Antarctic sea ice

Two groups of halotolerant, strictly oxidative, non-motile bacterial strains with a distinct coccoidal morphology were isolated from predominantly congelation sea ice collected from the Vestfold Hills area (69°S 78°E) and from anchor ice of the Amery Ice Shelf (69°S 71°E) in Eastern Antarctica. One group of strains were found to be phenotypically similar to the species Psychrobacter immobilis. This relationship was confirmed by DNA:DNA hybridization which showed representative strains shared 74-92% DNA homology with Psychrobacter immobilis ACAM 521(T) (T, type strain). A second group of strains possessed an optimal temperature for growth of 13-15°C, and required seawater for optimal growth and failed to form acid from carbohydrates. These strains were also halotolerant growing in the presence of NaCl concentrations up to 1.8-2.1 M. Further characterization studies determined that the strains belonged to a single distinct taxon within the genus Psychrobacter which differed phenotypically and genotypically from other Psychrobacter species isolated from Antarctica and other environments. Psychrobacter urativorans ACAM 534(T) was the closest phylogenetic relative to the novel sea ice taxa in terms of 16S rDNA sequence similarity of 96.7%. The sea ice strains thus represent a novel species within the genus Psychrobacter with the proposed name, Psychrobacter glacincola sp. nov. (type strain = ACAM 483(T)).