Degradation of mixtures of aromatic and chloroaliphatic hydrocarbons by aromatic hydrocarbon-degrading bacteria

The well-characterized toluene-oxidizing bacteria Pseudomonas putida PaW1, P. putida F1, P. mendocina KR1, Burkholderia cepacia G4, B. cepacia JS150, and Ralstonia pickettii PKO1, as well as several strains of bacteria isolated from activated sludge, were examined for their ability to degrade mixtures of aromatic and chloroaliphatic hydrocarbons. Collectively, the strains tested were able to transform all of the 14 aromatic hydrocarbons included in the mixtures, with most strains degrading five or more. Few strains degraded trichloroethylene well under these conditions, only one degraded methylene chloride, and none were able to transform chloroform. G4, PKO1, KR1, F1, and JS150 exhibited generally broad but oxygenase-specific degradation profiles, with the three monooxygenase strains degrading significantly more o-xylene and trichloroethylene, and F1 and JS150 degrading greater quantities of isopropylbenzene and 1,4-dichlorobenzene. PaW1 degraded only the methylaromatic hydrocarbons and styrene. Sludge isolates enriched on benzene, toluene, styrene and the xylenes exhibited degradation profiles similar to F1 or PaW1, while the pattern of hydrocarbon degradation for the ethylbenzene, isopropylbenzene, 1,3,5-trimethylbenzene, and 1,3-dichlorobenzene isolates were distinct from the other strains and from each other. Overall, our results showed that many of the bacteria which utilize aromatic compounds are capable of degrading a diverse array of aromatic hydrocarbons in mixtures, but that chloroaliphatics such as methylene chloride and chloroform may be recalcitrant to co-oxidation in the presence of aromatics or trichloroethylene.