Pseudonocardia dioxanivorans CB1190 is a monooxygenase-expressing bacterium capable of biodegrading 1,4-dioxane, a water contaminant and a probable human carcinogen.  We measured lower 1,4-dioxane biodegradation rates in the presence of 0-100 mg/L copper salts and determined likely mechanisms of toxicity.  Addition of cysteine and tannin mitigated inhibitory effects of copper on 1,4-dioxane biodegradation.  P. dioxanivorans CB1190 cultures were analyzed for ATP concentrations, respiration, antioxidant activity, membrane integrity, and reactive oxygen species (ROS).  ATP content, thiol concentrations, and metabolic activity decreased with increase in copper concentrations, demonstrating that copper reduced cell viability.  Furthermore, increases in various ROS were observed in copper-exposed cultures.  Amplification of gene transcripts for metal resistance, cellular stress, and dioxane monooxygenase corroborated the results of physiological assays.  Thus, 1,4-dioxane biodegradation in the presence of copper will be limited via inhibition of the monooxygenase enzyme, and by the depletion of overall cell viability as a consequence of ROS production.

Mechanistic toxicology of copper in a 1,4-dioxane degrading bacterium

248th National Meeting (2014)

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