MOLYBDENUM INCORPORATION IN DENITRIFYING AZOSPIRILLUM-BRASILENSE SP7

Nondenaturating disc gel electrophoresis revealed that Mo-99 was incorporated into the nitrate reductase of Azospirillum brasilense grown in the absence but not in the presence of tungstate. Under denitrifying conditions, A. brasilense grown in tungsten-free medium steadily accumulated Mo-99 for 12 h. In contrast, Paracoccus denitrificans grown under the same conditions ceased uptake after 1 h. However, both bacteria were incapable of accumulating significant amounts of Mo-99 in media containing 10 mM tungstate, even though nitrate was reduced by A. brasilense. Aerobically grown A. brasilense cells transported Mo-99 more efficiently than anaerobically grown cells.