| Bacteria possess immense metabolic diversity allowing them to degrade virtually all organic compounds introduced into the biosphere. The abilities of bacteria to degrade organic compounds that act as contaminants in the environment may prove useful in remediation efforts. This study examines the ability of three soil isolates to degrade aromatic hydrocarbons in axenic and defined mixed cultures. Mycobacterium vaccae strain JOB-5 possesses a propane monooxygenase with broad substrate specificity that is able to oxidize a wide range of mononuclear aromatic hydrocarbons including benzene, toluene, xylene, ethylbenzene, propylbenzene, isopropylbenzene, styrene, and chlorobenzene. M. vaccae biotransformation products can adversely effect further degradation by M. vaccae and are potentially a greater health threat than the parent compounds. Two rhodococci species, when added with M. vaccae in a defined mixed culture, were able to degrade a wider range of aromatic substrates as well as many of the transformation products than occurred with M. vaccae alone. Rhodococcus equi strain R-22 can catabolize the M. vaccae biotransformation products phenol, 4-ethylphenol, 4-chlorophenol, and styrene oxide, but cannot metabolize unoxidized aromatic substrates. Rhodococcus sp. strain B-58 can utilize benzene, toluene, and ethylbenzene as growth substrate and degrades phenol, 4-ethylphenol, 4-propylphenol, 4-isopropylphenol, and styrene oxide. A mixture of M. vaccae and B-58 degraded the BTX and BTEX mixture of aromatic compounds below detectable levels with no product accumulation. Defined mixed cultures may prove useful for studying microbial systems and in bioremediation. |
