Pradel, Nathalie

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.3.5.2T 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-2T (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-C15 : 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.3.5.2T (=DSM 107166T=NBRC 114655T) 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.

Summary Multicellular magnetotactic prokaryotes ( MMPs ) are a peculiar group of magnetotactic bacteria, each comprising approximately 10–100 cells of the same phylotype. Two morphotypes of MMP have been identified, including several species of globally distributed spherical mulberry‐like MMPs (s‐ MMPs ), and two species of ellipsoidal pineapple‐like MMPs (e‐ MMPs ) from C hina ( Q ingdao and R ongcheng cities). We recently collected e‐ MMPs from M editerranean S ea sediments ( S ix‐ F ours‐les‐ P lages) and D rummond I sland, in the S outh C hina S ea. Phylogenetic analysis revealed that the MMPs from S ix‐ F ours‐les‐ P lages and the previously reported e‐ MMP C andidatus   M agnetananas rongchenensis have 98.5% sequence identity and are the same species, while the MMPs from D rummond I sland appear to be a novel species, having > 7.1% sequence divergence from the most closely related e‐ MMP , C andidatus   M agnetananas tsingtaoensis. Identification of the novel species expands the distribution of e‐ MMPs to T ropical Z one. Comparison of nine physical and chemical parameters revealed that sand grain size and the content of inorganic nitrogen (nitrate, ammonium and nitrite) in the sediments from R ongcheng C ity and S ix‐ F ours‐les‐ P lages were similar, and lower than found for sediments from the other two sampling sites. The results of the study reveal broad diversity and wide distribution of e‐ MMPs .