| Summary: | Several closely related Mn(II)-oxidizing alpha-Proteobacteriawere isolated from very different marine environments: strainSI85-9A1 from the oxic/anoxic interface of a stratified Canadianfjord, strain HTCC 2156 from the surface waters off the Oregoncoast, and strain AE01 from the dorsal surface of a hydrothermalvent tubeworm. 16S rRNA analysis reveals that these isolatesare part of a tight phylogenetic cluster with previously characterizedmembers of the genus Aurantimonas. Other organisms withinthis clade have been isolated from disparate environments such assurface waters of the Arctic and Mediterranean seas, a deep-seahydrothermal plume, and a Caribbean coral. Further analysis ofall these strains revealed that many of them are capable of oxidizing dissolved Mn(II) and producing particulate Mn(III/IV) oxides.Strains SI85-9A1 and HTCC 2156 were characterized further. Despite sharing nearly identical 16S rRNA gene sequences with the previously described Aurantimonas coralicida,whole genome DNADNA hybridization indicated that their overall genomic similarity is low. Polyphasic phenotype characterization further supported distinguishing characteristics among these bacteria. Thus SI85-9A1 and HTCC 2156 are described as two new species within the family ‘Aurantimonadaceae’: Aurantimonas manganoxydanssp. nov. and Aurantimonas litoralis sp. nov. This clade of bacteria is widely distributed around the globe and may be important contributors to Mn cycling in many environments. Our results highlight the difficulty in utilizing 16S rRNA-based approaches to investigate the microbial ecology of Mn(II) oxidation.
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