Geomonas silvestris sp. nov., Geomonas paludis sp. nov. and Geomonas limicola sp. nov., isolated from terrestrial environments, and emended description of the genus Geomonas

Three bacterial strains, designated Red330(T), Red736T and Red745(T), were isolated from forest and paddy soils in Japan. Strains Red330(T), Red736(T) and Red745(T) are flagella-harbouring and strictly anaerobic bacteria forming red colonies. A 16S rRNA gene sequence -based phylogenetic tree showed that all three strains were located in a cluster, including the type strains of Geomonas species, which were recently separated from the genus Geobacter within the family Geobacteraceae. Similarities of the 16S rRNA gene sequences among the three strains and Geomonas oryzae S43(T), the type species of the genus Geomonas, were 96.3-98.5 %. The genome-related indexes, average nucleotide identity, digital DNA-DNA hybridization, and average amino acid identity, among the three strains and G. oryzae S43(T) were 74.7-86.8 %, 21.2?33.3 % and 70.4-89.8 %, respectively, which were lower than the species delineation thresholds. Regarding the phylogenetic relationships based on genome sequences, the three strains clustered with the type strains of Geomonas species, which were independent from the type strains of Geobacter species. The distinguishableness of the three isolated strains was supported by physiological and chemotaxonomic properties, with the profile of availability of electron donors and cellular fatty acids composition being particularly different among them. Based on genetic, phylogenetic and phenotypic properties, the three isolates represent three novel independent species in the genus Geomonas, for which the names Geomonas silvestris sp. nov., Geomonas paludis sp. nov. and Geomonas limicola sp. nov. are proposed. The type strains are Red330(T) (=NBRC 114028(T)=MCCC 1K03949(T)), Red736(T) (=NBRC 114029(T)=MCCC 1K03950(T)) and Red745(T) (=NBRC 114030(T)=MCCC 1K03951(T)), respectively.

Automated summary

Three novel bacterial strains were isolated from soil in Japan, identified as new species in the genus Geomonas based on 16S rRNA gene sequences and genome-related analysis, named Geomonas silvestris sp. nov., Geomonas paludis sp. nov., and Geomonas limicola sp. nov.