1,4-Dioxane is a commonly used industrial solvent stabilizer, a groundwater contaminant, and a probable human carcinogen. Due to its chemical and physical properties, treatment of 1,4-dioxane-contaminated groundwater is not cost effective. Two well-studied oxygenase-expressing bacteria Mycobacterium vaccae JOB5 (referred as JOB5 hereafter) and Rhodococcus jostii RHA1 (referred as RHA1 hereafter) have been shown to individually degrade both 1,4-dioxane and common co-contaminants, e.g. trichloroethylene (TCE) and trichloropropane (TCP). However, little study has been devoted to the biodegradation of both 1,4-dioxane and co-contaminants. To determine the effects of co-contaminants on 1,4-dioxane biodegradation, strains JOB5 and RHA1 were used to degrade 1,4-dioxane and mixtures of 1,4-dioxane and TCE or 1,4-dioxane and TCP. Propane- and 1-butanol-induced JOB5 and RHA1 were able express oxygenases to degrade both 1,4-dioxane, TCE, and TCP. Complete degradation of 1,4-dioxane/TCE mixture was only observed in propane-induced strain JOB5. Product toxicity caused incomplete degradation of 1,4-dioxane by 1-butanol-induced JOB5. Furthermore, competitive inhibition was observed between 1,4-dioxane and TCE in propane- and 1-butanol-induced JOB5 and RHA1. The findings of this study provide a major basis for developing an effective in-situ remediation method for 1,4-dioxane-contaminated ground water
