Effects of electron transport inhibitors and uncouplers on denitrification in Paracoccus denitrificans

Abstract Gaschromatographic analysis shows that whole cells of Paracoccus denitrificans produce dinitrogen in the absence and nitrous oxide in the presence of thiocyanate during nitrate reduction. NADH nitrate reductase activity in vesicles is much more sensitive to thiocyanate than either NADH oxidase activity in vesicles or reduction of nitrate by endogenous substrates in whole cells. NADH nitrate reductase activity is not inhibited and NADH oxidase activity is partially inhibited by antimycin A in vesicles. Production of nitrous oxide from nitrate in cells is completely inhibited by the simultaneous presence of thiocyanate and Triton X-100. Carbonylcyanide m -chlorophenylhydrazone does not cause a lag phase in reduction of nitrate by NADH in vesicles, in contrast to the situation in cells.