Heterotrophic nitrification by intestinal microorganisms.

From studies of nitrate balance in man and analyses of fecal and ileostomy samples, the possibility that nitrite and nitrate are formed de novo in the intestine, possibly by heterotrophic nitrification has emerged. This proposition significantly alters our previous conceptions of man's exposure to nitrite and suggests that nitrite may play a role in the cause of intestinal cancer. Heterotrophic nitrification has been demonstrated in various microorganisms. Our work has shown that intestinal heterotrophic microbial isolates from man are able to oxidize nitrogenous compounds to nitrite. These isolates include both procaryotes and eucaryotes.