Mechanism controlling the extended lag period associated with vinyl chloride starvation in Nocardioides sp. strain JS614
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The extended lag period associated with vinyl chloride (VC) starvation in VC- and ethene-assimilating Nocardioides sp. strain JS614 was examined. The extended lag periods were variable (3–7 days), only associated with growth on VC or ethene, and were observed in VC- or ethene-grown cultures following 24 h carbon starvation and mid-exponential phase cultures grown on non-alkene carbon sources (e.g. acetate). Alkene monooxygenase (AkMO) and epoxyalkane:coenzyme M transferase (EaCoMT) are the initial enzymes of VC and ethene biodegradation in strain JS614. Reverse-transcription PCR confirmed that the AkMO gene etnC was expressed in response to epoxyethane, a metabolic intermediate of ethene biodegradation. Epoxyethane (0.5 mM) eliminated the extended lag period in both starved and mid-exponential phase cultures, suggesting that epoxyethane accumulation activates AkMO expression in strain JS614. AkMO activity in ethene-grown cultures was not detected after 6.7 h of carbon starvation, while 40% of the initial EaCoMT activity remained after 24 h. Acetate eliminated the extended lag period in starved cultures but not in mid-exponential phase cultures suggesting that acetate reactivates extant AkMO in starved VC- or ethene-grown cultures. The imbalance between AkMO and EaCoMT activities during starvation likely contributes to the extended lag period by delaying epoxide accumulation and subsequent AkMO induction.
KeywordsVinyl Chloride Minimal Salt Medium Carbon Starvation Hewlett Packard Nocardioides
We thank Juli Rubin, Brian Weisenstein, Linda Rankin, Julie Karceski, and Yang Oh Jin for technical assistance. We also thank Anthony Hay, Ruth Richardson, and Steve Zinder for use of their laboratories and for valuable advice. The U.S. National Science Foundation-supported Center for Environmentally Beneficial Catalysis (NSF award EEC-0310689), the U.S. Strategic Environmental Research and Development Program (SERDP), and The University of Iowa contributed funding for this work.
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