Aminithiophilus ramosus gen. nov., sp. nov., a sulphur- reducing bacterium isolated from a pyrite- forming enrichment culture, and taxonomic revision of the family Synergistaceae

A novel sulphur-reducing bacterium was isolated from a pyrite-forming enrichment culture inoculated with sewage sludge from a wastewater treatment plant. Based on phylogenetic data, strain J.5.4.2-(T). 3.5.2(T) could be affiliated with the phylum Synergistota. Among type strains of species with validly published names, the highest 16S rRNA gene sequence identity value was found with Aminiphilus circumscriptus ILE-2(T) (89.2%). Cells of the new isolate were Gram-negative, non-spore-forming, straight to slightly curved rods with tapered ends. Motility was conferred by lateral flagella. True branching of cells was frequently observed. The strain had a strictly anaerobic, asaccharolytic, fermentative metabolism with peptides and amino acids as preferred substrates. Sulphur was required as an external electron acceptor during fermentative growth and was reduced to sulphide, whereas it was dispensable during syntrophic growth with a Methanospirillum species. Major fermentation products were acetate and propionate. The cellular fatty acid composition was dominated by unsaturated and branched fatty acids, especially iso-C (15:0). Its major polar lipids were phosphatidylglycerol, phosphatidylethanolamine and distinct unidentified polar lipids. Respiratory lipoquinones were not detected. Based on the obtained data we propose the novel species and genus Aminithiophilus ramosus, represented by the type strain J.5.4.2-T. 3.5.2(T) (=DSM 107166(T)=NBRC 114655(T)) and the novel family Aminithiophilaceae fam. nov. to accommodate the genus Aminithiophilus. In addition, we suggest reclassifying certain members of the Synergistaceae into new families to comply with current standards for the classification of higher taxa. Based on phylogenomic data, the novel families Acetomicrobiaceae fam. nov., Aminiphilaceae fam. nov., Aminobacteriaceae fam. nov., Dethiosulfovibrionaceae fam. nov. and Thermovirgaceae fam. nov. are proposed.

Automated summary

A novel sulphur-reducing bacterium was isolated from sewage sludge in a wastewater treatment plant. It belongs to the phylum Synergistota and is anaerobic with a fermentative metabolism using peptides and amino acids as substrates. We propose the new species and genus Aminithiophilus ramosus and suggest reclassifying certain members of the Synergistaceae into new families based on phylogenomic data.