Physiological and molecular genetic analyses of vinyl chloride and ethene biodegradation in Nocardioides sp. strain JS614

Abstract

Nocardioides sp. strain JS614 utilizes vinyl chloride and ethene as carbon and energy sources. JS614 could be influential in natural attenuation and biogeochemical ethene cycling, and useful for bioremediation, biocatalysis and metabolic engineering, but a fundamental understanding of the physiological and genetic basis of vinyl chloride and ethene assimilation in strain JS614 is required. Alkene monooxygenase (AkMO) activity was demonstrated in whole-cell assays and epoxyalkane:coenzyme M transferase (EaCoMT) activity was detected in JS614 cell-free extracts. Pulsed-field gel electrophoresis revealed a 290-kb plasmid (pNoc614) in JS614. Curing experiments and PCR indicated that pNoc614 encodes vinyl chloride/ethene-degradation genes. JS614 vinyl chloride/ethene catabolic genes and flanking DNA (34.8 kb) were retrieved from a fosmid clone. AkMO and EaCoMT genes were found in a putative operon that included CoA transferase, acyl-CoA synthetase, dehydrogenase, and reductase genes. Adjacent to this gene cluster was a divergently transcribed gene cluster that encoded possible coenzyme M biosynthesis enzymes. Reverse transcription-PCR demonstrated the vinyl chloride- and ethene-inducible nature of several genes. Genes encoding possible plasmid conjugation, integration, and partitioning functions were also discovered on the fosmid clone.