Rhodococcus biphenylivorans sp. nov., a polychlorinated biphenyl-degrading bacterium.

Abstract

A Gram-positive, aerobic, non-motile and rod-coccus shaped novel actinobacterial strain, designated as TG9(T), was isolated from a polychlorinated biphenyl (PCB)-contaminated sediment in Taizhou city, Zhejiang province, eastern China. The isolate was observed to grow at 10-45°C (optimum 28-32°C), pH 5.0-11.0 (optimum pH 7.0-8.0) and with 0-9.0% (w/v) NaCl (optimum 0-3.0%). Comparison of the 16S rRNA gene sequences of strain TG9(T) and other members of the genus Rhodococcus showed that strain TG9(T) shared highest similarities with Rhodococcus pyridinivorans DSM 44555(T) (99.4%), R. rhodochrous DSM 43241(T) (99.2%), R. gordoniae DSM 44689(T) (99.2%) and R. artemisiae DSM 45380(T) (98.2%). However, low levels of DNA-DNA relatedness (15-48%), which are below the 70% limit for prokaryotic species identification, were obtained by DNA-DNA hybridization. Strain TG9(T) was found to contain meso-diaminopimelic acid as the diagnostic diamino acid and arabinose and galactose in the whole-cell hydrolysate. Mycolic acids were found to be present. The major fatty acids were identified as C16:0, C16:1 ω7c and/or iso-C15:0 2-OH, 10-methyl C18:0 and C18:1 ω9c. The only menaquinone detected was MK-8 (H2). The major polar lipids detected were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, glycolipid and traces of some unknown lipids. The genomic DNA G+C content of strain TG9(T) was determined to be 62.8%. The combined phenotypic and genotypic data show that the strain represents a novel species of the genus Rhodococcus for which the name Rhodococcus biphenylivorans sp. nov. is proposed, with the type strain TG9(T) (=CGMCC 1.12975(T)=KCTC 29673(T)=MCCC 1K00286(T)).