Degradation of pyridines in the environment

Pyridine and pyridine derivatives occur in the environment as a result of industrial and agricultural activities. The fate of pyridines in the environment is a function of both abiotic and biotic processes, including photochemical transformations, complexation, surface attenuation, transport, and biological degradation. Pyridine is readily degraded in soil, and numerous bacteria isolated from soils or sludges are capable of growing on pyridines as sole sources of carbon and/or nitrogen. Numerous substituted pyridines are also susceptible to biodegradation, although major changes in biodegrada‐bility of the pyridine ring result from slight modification of the nature orposition of ring substituents. Bacteria apparently degrade most simple pyridine derivatives, particularly hydroxypyridines and pyridinecarboxylic acids, via pathways involving hydroxylated intermediates. The initial hydroxylation step in biodegradation of many pyridines is unusual in the incorporation of oxygen derived from water. Data suggest that pyridine and some substituted pyridines are degraded via novel mechanisms, possibly involving initial reductive steps, and lacking hydroxylated intermediates ubiquitous in the metabolism of other aromatic compounds. Data are lacking on the environmental fate of alkyl‐ and chloropyridines, which constitute two of the most important classes of pyridine derivatives detected in environmental samples.