Vibrio mangrovi sp. nov., a diazotrophic bacterium isolated from mangrove-associated wild rice (Poteresia coarctata Tateoka)

Abstract

The taxonomic status of a nitrogen-fixing bacterium, strain MSSRF38(T), isolated from the rhizosphere of mangrove-associated wild rice (Porteresia coarctata Tateoka), in Pichavaram, India, was studied using a polyphasic approach. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the novel strain MSSRF38(T) was most closely related to Vibrio ruber DSM 16370(T) (98.3% gene sequence similarity), Vibrio rhizosphaerae DSM 18581(T) (98.2% sequence similarity) and <96% to the remaining Vibrio species. Multilocus sequence analysis using ftsZ, gapA, gyrB and mreB genes showed low levels of gene sequence similarities (82-90%) with all species of the genus Vibrio with validly published names, indicating that strain MSSRF38(T) occupies a distinct phylogenetic position. DNA-DNA hybridization experiments showed that strain MSSRF38(T) had <70% DNA-DNA similarity to its closest neighbours V. ruber DSM 16370(T) (27.4%) and V. rhizosphaerae DSM 18581(T) (12.1%). Strain MSSRF38(T) could be differentiated from its relatives on the basis of several phenotypic characteristics. The major fatty acids were feature 3 (including C(16:1omega)7c and/or C(15:0) iso 2-OH), C16:0, C(18:1omega)7c, C(14:0) and C(12:0). The DNA G+C content was 45.4 mol%. Based on genotypic, phenotypic, chemotaxonomic and DNA-DNA analyses, the name Vibrio mangrovi sp. nov. (type strain MSSRF38(T)=LMG 24290(T)=DSM 19641(T)) is proposed for this novel taxon.