Abstract

Two Gram-staining-negative strains, designated SG184(T) and SG263(T) were isolated from paddy soils in Fujian Province, China. The 16S rRNA gene sequence similarities between strains SG184(T), SG263(T), and the related type strain Geothrix fermentans DSM 14018(T) were 98.6% and 99.1%, respectively. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) between the two strains and G. fermentans DSM 14018(T) were below the cut-off level (95% for ANI and 70% for dDDH) recommended as the criterion for interspecies taxon affiliation. Further, phylogenetic and phylogenomic trees indicated that strains SG184(T) and SG263(T) clustered with the member of the genus Geothrix. The menaquinone was MK-8, and the main fatty acids were iso-C-15:0 and iso-C-13:0 3OH. The genomic DNA G + C content of SG184(T) and SG263(T) was 68.07% and 68.05%, respectively. Additionally, two strains had iron reduction ability and could reduce ferrihydrite to ferrous iron. Based on the morphological, biochemical, chemotaxonomic and genome analysis, the two isolated strains represent two novel species of the genus Geothrix, for which the names Geothrix terrae sp. nov. and Geothrix alkalitolerans sp. nov. are proposed. The type strains are SG184(T) (= GDMCC1.3134 (T) = JCM39321(T)) and SG263(T) (= GDMCC 1.3316 (T) = JCM 39325(T)), respectively.