AEROBIC BIODEGRADATION OF 4-METHYLQUINOLINE BY A SOIL BACTERIUM

Methylquinolines and related N-heterocyclic aromatic compounds are com mon contaminants associated with the use of hydrocarbons in both coal gasification and wood treatment processes, These compounds have been f ound in groundwater, and many are known mutagens. A stable, five-membe r bacterial consortium able to degrade 4-methylquinoline was establish ed by selective enrichment using soil collected from an abandoned coal gasification site. The consortium was maintained for 5 years by seria l transfer in a medium containing 4-methylquinoline. A gram-negative s oil bacterium, strain Lep1, was isolated from the consortium and shown to utilize 4-methylquinoline as a source of carbon and energy during growth in liquid medium, A time course experiment demonstrated that bo th the isolate Lep1 and the consortium containing Lep1 were able to de grade 4-methylquinoline under aerobic conditions, Complete degradation of 4-methylquinoline by either strain Lep1 alone or the consortium wa s characterized bg the production and eventual disappearance of 2-hydr oxy-4-methylquinoline, followed by the appearance and persistence of a second metabolite tentatively identified as a hydroxy-4-methylcoumari n. Currently, there is no indication that 4-methylquinoline degradatio n proceeds differently in the consortium culture compared with Lep1 al one, This is the first report of 4-methylquinoline biodegradation unde r aerobic conditions.