Studies on Soluble Cytochromes in Enterobacteriaceae

Abstract

1.Gas production from glucose-fermenting E. coli cells grown anaerobically with nitrite or ammonia as sole nitrogen source was compared. In nitrite-grown cells, gas formation during glucose fermentation was strikingly stimulated by the presence of nitrite, whereas nitrite inhibited completely the gas evolution by ammonia-grown cells. 2.The gas produced by nitrite-grown cells in response to nitrite addition consisted mostly of CO₂ which seemed to have been derived from an unknown endogenous substrate. The total production of CO₂ was proportional to the amount of nitrite added. Stoichiometry studies showed that one mole of nitrite was quantitatively reduced to ammonia, concomitant with the evolution of one mole of CO₂. 3. Evidence was presented indicating that cytochrome c-552 was involved in this CO₂ producing system coupled to nitrite reduction, because both the CO₂ evolution and nitrite reduction were strikingly decreased when intact cells were freed from cytochrome c-552 by converting them into spheroplasts, and these activities could be restored by the addition of cytochrome c-552. 4. It was suggested that a sulfhydryl group and factors or sites sensitive to cyanide, azide, and HOQNO may be involved in the activity of the nitrite-dependent CO₂ producing system.