Nitrogen fixation by reductively dechlorinating bacteria.

Significant advances in the ecology, physiology and genetics of reductively dechlorinating bacteria have revealed their important environmental roles in bioremediation and in the global chlorine cycle. N2 fixation has been widely observed in symbiotic, associative and free-living bacteria. Here we show physiological and molecular evidence that reductively dechlorinating bacteria are capable of fixing atmospheric nitrogen. Furthermore, N2 fixation in some of these dechlorinating bacteria stimulated reductive dechlorination, which should help predict and regulate the environmental function of dechlorinating bacteria in in situ bioremediation of chlorinated pollutants. These results imply that N2 fixation in dechlorinating bacteria interacts with other biogeochemical cycles to control the nitrogen status of the anaerobic ecosystem.