Azospira inquinata sp. nov., a nitrate-reducing bacterium of the family Rhodocyclaceae isolated from contaminated groundwater

Abstract

Two novel Gram-stain-negative bacterial strains, Azo-3T and Azo-2, were isolated from a toluene-producing enrichment culture that originated from contaminated groundwater at a site in southeast Louisiana (USA). Cells are non-spore forming straight to curved rods with single polar flagella. Strains Azo-3T and Azo-2 are oxidase-positive, catalase-negative, use nitrate and nitrite as electron acceptors, and are able to fix nitrogen. Poly-β-hydroxybutyrate storage granules are produced. Dominant fatty acids when grown in R2A medium at 37 °C are C16:0, summed feature 3 (C16:1 ω7c and/or C15:0 iso 2OH), C17:0 cyclo and C18:1 ω7c. 16S rRNA gene sequence based phylogenetic analysis indicated that the strains cluster within the family Rhodocyclaceae , class Betaproteobacteria , most closely related to but distinct from type strains of the species Azospira oryzae (96.94% similarity) and Azospira restricta (95.10% similarity). Complete genome sequences determined for strains Azo-3T and Azo-2 revealed DNA G+C content of 62.70 mol%. Genome-wide comparisons based on average nucleotide identity by orthology and estimated DNA–DNA hybridization values combined with phenotypic and chemotaxonomic traits and phylogenetic analysis indicate that strains Azo-3T and Azo-2 represent a novel species within the genus Azospira for which the name Azospira inquinata sp. nov. is proposed. The type strain of Azospira inquinata is Azo-3T (=NRRL B-65590T=DSM 112046T).