Geothrix fuzhouensis sp. nov. and Geothrix paludis sp. nov., two novel Fe(III)-reducing bacteria isolated from paddy soil

Two anaerobic, Fe(III)-reducing and Gram-stain-negative strains, designated SG12 T and SG195 T , were isolated from paddy soils in Fujian Province, PR China. Phylogenetic trees based on 16S rRNA genes and conserved core genes from genomes indicated that strains SG12 T and SG195 T clustered with members of the genus Geothrix. The two strains showed the highest 16S rRNA sequences similarities to the type strains of ‘ Geothrix terrae ’ SG184 T (98.4–99.6 %), ‘ Geothrix alkalitolerans ’ SG263 T (98.4–99.6 %) and Geothrix fermentans DSM 14018 T (98.2–98.8 %). The average nucleotide identity and digital DNA–DNA hybridization values between the two strains and the closely related Geothrix species were 85.1–93.5 % and 29.8–52.9 %, respectively, lower than the cut-off level for prokaryotic species delineation. The menaquinone was MK-8 in both strains. The major fatty acids were iso-C 15 : 0 , anteiso-C 15 : 0 and C 16 : 0 . Additionally, the two strains possessed iron reduction ability and could utilize organics such as benzene and benzoic acid as electron donors to reduce ferric citrate to ferrous iron. Based on the morphological, biochemical, chemotaxonomic and genome data, the two isolated strains represent two novel species of the genus Geothrix , for which the names Geothrix fuzhouensis sp. nov. and Geothrix paludis sp. nov. are proposed. The type strains are SG12 T (=GDMCC 1.3407 T =JCM 39330 T ) and SG195 T (= GDMCC 1.3308 T =JCM 39327 T ), respectively.