Lily Y. Young
Chair and Professor II
Department of Environmental Sciences
Rutgers University
Abstract
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A Petroleum hydrocarbons enter the environment through both natural and anthropogenic processes. Oxygenase mediated processes are well described for the aerobic biodegradation of alkanes, mono- and polycyclic aromatic hydrocarbons (PAH). Once in the environment, however, if they are not degraded in the aerobic zones, they accumulate and eventually reside in anoxic regions of the soil or sediment. The fate of these compounds in these environments has recently come to light. In the absence of oxygen, pathways for the metabolism of these highly reduced compounds are now being reported. Effort in our lab has focused on the biodegradation of PAHs and alkanes under sulfidogenic conditions where two different mechanisms of attack have been observed. For both the PAHs and medium length alkanes (e.g. hexadecane) there can be a carboxylation of inorganic carbonate. For the alkanes, in one strain of sufate-reducers the initial inorganic carboxylation appears to be at the C-3 position. In another anaerobic organism, a very different method of attack takes place at the C-2 position. Interestingly, this second method of attack appears to be similar to the fumarate addition first observed for toluene. These activities appear to be found in a variety of anaerobes which are physiologically and phylogenetically different including sufate-reducers and denitrifiers suggesting that these processes may be widely distributed in the environment. From a practical standpoint, these unusual pathways also provide metabolites which can serve as specific indicators of in situ activity and this will be discussed. |