Geomesophilobacter sediminis gen. nov., sp. nov., Geomonas propionica sp. nov. and Geomonas anaerohicana sp. nov., three novel members in the family Geobacterecace isolated from river sediment and paddy soil

Mesoterricola silvestris gen. nov., sp. nov., Mesoterricola sediminis sp. nov., Geothrix oryzae sp. nov., Geothrix edaphica sp. nov., Geothrix rubra sp. nov., and Geothrix limicola sp. nov., six novel members of Acidobacteriota isolated from soils

Forty-eight Acidobacteriota strains were isolated from soils and sediments in Japan. Among them, six representative strains, designated W79T, W786T, Red222T, Red802T, Red803T, and Red804T, were subjected to the taxonomic classification. These six strains are Gram-stain-negative, non-spore-forming, rod-shaped, and facultative anaerobic bacterium that can reduce ferric iron. Phylogenetic and phylogenomic trees based on 16S rRNA genes and multiple single-copy gene sequences showed that strains Red222T, Red802T, Red803T, and Red804T formed a cluster with the type strains of Geothrix species, but strains W79T and W786T created an independent cluster from any other type strains. The former four strains shared 97.95-99.08% similarities of 16S rRNA gene sequence with the type strains of the genus Geothrix, whereas the latter two strains 94.86-95.49% similarities. The average amino acid identity of strains W79T and W786T were <63 % to any other type strains, which were below the genus delineation thresholds. Moreover, colonies of these two strains were white, while those of the other four isolated strains were reddish-yellow as well as the type strain Geothrix fermentans H-5T. Although the known type strains of Geothrix species have been reported to be non-motile, five strains (W79T, W786T, Red222T, Red803T, and Red804T) except for strain Red802T displayed motility. Furthermore, multiple genomic, phylogenetic, and phenotypic features supported the discrimination between these isolated strains. Based on the study evidence, we propose these six isolates as novel members within the Acidobacteriota/Holophagae/Holophagales/Holophagaceae, comprising two novel species of a novel genus, Mesoterricola silvestris gen. nov., sp. nov., and Mesoterricola sediminis sp. nov., and four novel species of the genus Geothrix: Geothrix oryzae sp. nov., Geothrix edaphica sp. nov., Geothrix rubra sp. nov., and Geothrix limicola sp. nov.

Anaeromyxobacter oryzae sp. nov., Anaeromyxobacter diazotrophicus sp. nov. and Anaeromyxobacter paludicola sp. nov., isolated from paddy soils

Three bacterial strains (Red232T, Red267T and Red630T) were isolated from paddy soils sampled in Japan. Cells of these strains were Gram-stain-negative, facultative anaerobic, long rod-shaped with monotrichous flagella or pilus-like structures for motility, and formed red colonies on agar plates. Phylogenetic trees based on 16S rRNA gene and multiple single-copy gene sequences showed that the three strains formed a cluster with the type strains of Anaeromyxobacter species, independent from any other strain genera. Similarity values of the 16S rRNA gene sequences and genomes among the three isolated strains and the type strain of Anaeromyxobacter , Anaeromyxobacter dehalogenans 2CP-1T, were 95.4–97.4% for 16S rRNA gene sequence, 75.3–79.5% for average nucleotide identity, 19.6–21.7% for digital DNA–DNA hybridization and 64.1–72.6% for average amino acid identity, all of which are below the species delineation thresholds. Nitrogenase genes were observed in the genomes of the three novel strains, but not in A. dehalogenans 2CP-1T. Moreover, multiple genomic, physiological and chemotaxonomic features supported the discrimination between these three strains. Based on the evidence in this study, the three isolates represent three novel independent species for which the following names are proposed: Anaeromyxobacter oryzae sp. nov., Anaeromyxobacter diazotrophicus sp. nov. and Anaeromyxobacter paludicola sp. nov. The type strains are Red232T (=NBRC 114074T=MCCC 1K03954T), Red267T (=NBRC 114075T=MCCC 1K04211T), and Red630T (=NBRC 114076T=MCCC 1K03957T), respectively.