Duganella kummerowiae sp. nov., a new bacterium isolated from root nodule of Kummerowia striata

A non-rhizobial endophyte bacterial strain, designated A2-2^T, was isolated from a root nodule of Kummerowia striata collected in Bin County, Heilongjiang Province of China. It was Gram-stain-negative, aerobic and non-motile and was able to grow at 15-37 ℃ in medium with 0-1% (wt/vol.) salinity and pH 5-11. It showed activities of oxidase and catalase and produced potential auxin-related compounds. Phylogenetic analysis based on the 16S rRNA gene sequences showed that strain A2-2^T was related to the type strains of Pseudoduganella namucuonensis, Pseudoduganella buxea, Pseudoduganella aquatica and Pseudoduganella plicata, having the highest sequence similarity (97.8%) with P. namucuonensis 333-1-0411^T; however, two phylogenomic trees, including GTDB-Tk and BV-BRC phylogenies, consistently placed the strain within the genus Duganella, where it formed an independent lineage. The ANI, dDDH and AAI values between strain A2-2^T and 23 validly published species of the genus Duganella were 77.4-80.8%, 21.5-28.9% and 69.5-75.9%, respectively, all of which were below the accepted species delineation thresholds. The genomic DNA G+C content of strain A2-2^T was 66.1 mol%. The strain lacked the nodC gene but harboured a relatively complete nif and fix genes. The main respiratory quinone of strain A2-2^T was ubiquinone-8, and its major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. The main cellular fatty acid components were summed feature 3, C_16 : 0 and summed feature 8. Based on the evidence obtained in this study, a novel species, Duganella kummerowiae sp. nov., is proposed and the type strain is A2-2^T (=JCM 38047^T=CCTCC AB 2025004^T).