Granulosicoccaceae fam. nov., to include granulosicoccus antarcticus gen. nov., sp. nov., a non-phototrophic, obligately aerobic chemoheterotroph in the order chromatiales, isolated from antarctic seawater

Abstract

A Gram-negative, motile by tuft flagella, obligately aerobic chemoorganoheterotrophic, sphere-form bacterium, designated IMCC3135T, was isolated from the Antarctic surface seawater of King George Island, West Antarctica. The strain was mesophilic, neutrophilic, and requiring NaCl for growth, but neither halophilic nor halotolerant. The 16S rRNA gene sequence analysis indicated that the strain was most closely related to genera of the order Chromatiales in the class Gammaproteobacteria. The most closely related genera showed less than 90% 16S rRNA gene sequence similarity and included Thioalkalispira (89.9%), Thioalkalivibrio (88.0%-89.5%), Ectothiorhodospira (87.9%-89.3%), Chromatium (88.3%-88.9%), and Lamprocystis (87.7%-88.9%), which represent three different families of the order Chromatiales. Phylogenetic analyses showed that this Antarctic strain represented a distinct phylogenetic lineage in the order Chromatiales and could not be assigned to any of the defined families in the order. Phenotypic characteristics, including primarily non-phototrophic, non-allcaliphilic, non-halophilic, and obligately aerobic chemoheterotrophic properties, differentiated the strain from other related genera. The very low sequence similarities (