Two ferric-reducing bacteria Geothrix terrae sp. nov. and Geothrix alkalitolerans sp. nov., isolated from paddy soil

Arch Microbiol. 2022 Nov 11;204(12):699. doi: 10.1007/s00203-022-03293-y.


Two Gram-staining-negative strains, designated SG184T and SG263T were isolated from paddy soils in Fujian Province, China. The 16S rRNA gene sequence similarities between strains SG184T, SG263T, and the related type strain Geothrix fermentans DSM 14018T 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 14018T 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 SG184T and SG263T clustered with the member of the genus Geothrix. The menaquinone was MK-8, and the main fatty acids were iso-C15:0 and iso-C13:0 3OH. The genomic DNA G + C content of SG184T and SG263T 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 SG184T (= GDMCC1.3134 T = JCM39321T) and SG263T (= GDMCC 1.3316 T = JCM 39325T), respectively.

Keywords: Fe(III)-reducing bacteria; Geothrix alkalitolerans sp. nov.; Geothrix terrae sp. nov.; Paddy soil.

MeSH terms

  • Bacteria / genetics
  • Bacterial Typing Techniques
  • DNA, Bacterial / genetics
  • Fatty Acids / analysis
  • Iron
  • Phylogeny
  • RNA, Ribosomal, 16S / genetics
  • Sequence Analysis, DNA
  • Soil Microbiology*
  • Soil*


  • RNA, Ribosomal, 16S
  • Soil
  • DNA, Bacterial
  • Fatty Acids
  • Iron