Aerobic Denitrification and Heterotrophic Sulfur Oxidation in the Genus Revealed by Six Novel Species Characterizations and Genome-Based Analysis.

Bacteria of are widely distributed in various environments and play a substantial role in the nutrient cycle. In this report, 14 strains capable of aerobic denitrification and heterotrophic sulfur oxidation were isolated from different habitats. Based on the phenotypic, genotypic, and chemotaxonomic analyses, these strains were considered to represent six novel species of the genus , for which the names sp. nov. type strain CXT3-11 ( = MCCC 1A11036 = KCTC 72087), sp. nov. CYD-9 ( = MCCC 1A11058 = KCTC 72088), sp. nov. CYN-1-2 ( = MCCC 1A11059 = KCTC 72089), sp. nov. CYT3-1-1 ( = MCCC 1A11081 = KCTC 72090), sp. nov. NLG_F1E ( = MCCC 1A13718 = KCTC 72091), and sp. nov. BC-M4-5 ( = MCCC 1A14433 = KCTC 72092) are proposed. Intriguingly, they formed a unique group with 11 other species designated as the " group." To better understand their featured metabolisms, genes involved in denitrification and sulfur oxidation were analyzed, along with 193 other available genomes of the whole genus. Consistently, complete denitrification pathways were confirmed in the " group," in which , , , , and genes coexist. Their nitrite reductase NirS formed a unique evolutionary lineage, distinguished from other denitrifiers in . In addition, diverse occurrence patterns of denitrification genes were also observed in different phylogenetic clades of . With respect to sulfur oxidation, genes involved in sulfide oxidation commonly exist in the " group," while genes are diverse and can be found in more species; genes co-occurred with in eight strains of this study, contributing to more active sulfide oxidation. Besides, the gene, which encodes an enzyme that oxidizes thiosulfate to tetrathionate, is ubiquitous in the genus . The widespread presence of , , and in suggests that many spp. can act as heterotrophic sulfur oxidizers. These results provide comprehensive insights into the potential of denitrification and sulfur oxidation in the whole genus of . With regard to the global distribution of , this report implies their unneglectable role in the biogeochemical cycle.