Reclassification of Sphaerotilus natans subsp. sulfidivorans Gridneva et al. 2011 as Sphaerotilus sulfidivorans sp. nov. and comparative genome analysis of the genus Sphaerotilus

Filamentous iron oxides accumulating bacteria Sphaerotilus natans subsp. natans and S . natans subsp. sulfidivorans were described as subspecies based on 99.7% identity of their 16S rRNA sequences, in spite of important physiological difference. The ANI between their genomes was 94.7%, which indicate their assignment to different species. S . natans subsp. sulfidivorans and S . montanus possess genes for a complete SOX system, while S . natans subsp. natans encode only SoxYZ. There are genes for the Calvin cycle in the genomes of S . hippei DSM 566 T , S . natans subsp. sulfidivorans D-501 T , and S . montanus HS T . Lithoautotrophy on reduced sulfur compounds is probably possible for S . natans subsp. sulfidivorans and S . montanus , but not for S . natans subsp. natans . Considering significant differences in the genome characteristics and metabolic potential of S . natans subsp. sulfidivorans and S . natans subsp. natans , we propose their classification as different species, S . natans and S . sulfidivorans sp. nov.