UTILIZATION OF TOLUENE AND XYLENES BY A NITRATE-REDUCING STRAIN OF PSEUDOMONAS-MALTOPHILIA UNDER LOW-OXYGEN AND ANOXIC CONDITIONS

A nitrate-reducing strain of Pseudomonas maltophilia isolated from sew age sludge degrades toluene, and at least two isomers of mixed xylenes , either in the presence of 2% oxygen or under anoxic conditions when nitrate is present. When individual isomers of xylene are provided onl y meta and para-xylene are utilized. When mixed xylenes are provided a ll three isomers may be utilized. In cultures limited by electron acce ptor availability, succinate, when present as the major carbon source, does not prevent hydrocarbon utilization. Toluene and xylenes continu ed to be utilized either with limiting nitrate alone, or with limiting nitrate and oxygen present simultaneously when a hundred-fold excess of succinate is present in the medium. The data suggest that in ground water containing low levels of oxygen and nitrate, or nitrate only as the electron acceptor, aromatic hydrocarbons may continue to be utiliz ed even in the presence of an excess of readily-degradable non-hydroca rbon organic substrates. These data have implications for bioremediati on studies. The strain of Pseudomonas maltophilia used in this study d oes not degrade benzene, and the presence of benzene does not affect t oluene utilization.