Acidovorax benzenivorans sp. nov., a novel aromatic hydrocarbon-degrading bacterium isolated from a xylene-degrading enrichment culture

Abstract

A Gram-stain-negative strain, designated as D2M1^T was isolated from xylene-degrading enrichment culture and characterized using a polyphasic approach to determine its taxonomic position. The 16S rRNA gene sequence analysis revealed that strain D2M1^T belongs to the genus Acidovorax, with the highest 16S rRNA gene similarity to Acidovorax delafieldii DSM 64^T (99.93 %), followed by Acidovorax radicis DSM 23535^T (98.77 %) and Acidovorax kalamii MTCC 12652^T (98.76 %). The draft genome sequence of strain D2M1^T is 5.49 Mb long, and the G+C content of the genome is 64.2 mol%. Orthologous average nucleotide identity and digital DNA-DNA hybridization relatedness values between strain D2M1^T and its closest relatives were below the threshold values for species demarcation confirming that strain D2M1^T is distinctly separated from its closest relatives. The whole genome analysis of the strain revealed a phenol degradation gene cluster, encoding a multicomponent phenol hydroxylase (mPH) together with a complete meta-cleavage pathway including an I.2.C-type catechol 2,3-dioxygenase (C23O) gene. The strain was able to degrade benzene and ethylbenzene as sole sources of carbon and energy under aerobic and microaerobic conditions. Cells were facultatively aerobic rods and motile with a single polar flagellum. The predominant fatty acids (>10 % of the total) of strain D2M1^T were summed feature 3 (C_{16 : 1} ω7c/C_{16 : 1} ω6c), C_{16 : 0} and summed feature 8 (C_{18 : 1} ω7c/C_{18 : 1} ω6c). The major ubiquinone of strain D2M1^T was Q8, while the major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. Based on polyphasic data, it is concluded that strain D2M1^T represents a novel species of the genus Acidovorax, for which the name of Acidovorax benzenivorans sp. nov. is proposed. The type strain of the species is strain D2M1^T (=DSM 115238^T=NCAIM B.02679^T).

Keywords: Acidovorax; Benzene; aromatic hydrocarbons; biodegradation.