Fundidesulfovibrio agrisoli sp. nov., A Nitrogen-Fixing Bacterium Isolated from Rice Field

A strictly anaerobic nitrogen-fixing strain, designated SG106^T, was isolated from rice field. The 16S rRNA gene sequence analysis showed that strain SG106^T was closely related to the type strain of Fundidesulfovibrio magnetotacticus (97.3%). In phylogenetic (based on 16S rRNA gene sequences) and phylogenomic (constructed using a concatenated alignment of 117 conserved bacterial single-copy genes with GTDB-Tk) trees, strain SG106^T clustered with members of the genus Fundidesulfovibrio. Strain SG106^T grew at 20-40 °C and 0-0.4% (w/v) NaCl. Desulfoviridin was found in the strain SG106^T. The genomic DNA G + C content of strain SG106^T was 66.0%. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain SG106^T and the closely related F. magnetotacticus were 78.4% and 21.7%, respectively. Genome analysis showed that strain SG106^T encodes genes for nitrogen fixation (nifHDK). Acetylene reduction experiments showed that the nitrogenase activity of strain SG106^T could reach 224.7 μmol C₂H₄ g^-1 protein h^-1. Based on the above results, strain SG106^T represents a novel species of the genus Fundidesulfovibrio, for which the name Fundidesulfovibrio agrisoli sp. nov. is proposed. The type strain is SG106^T (= GDMCC 1.3136^T = JCM 35588^T).