[The effect of nitrate and nitrite on the respiration and cytochrome system of Rhizobium lupini].

Differential spectrophotometry and oxygen electrode were used to study the effect of nitrate and nitrite on the cytochrome system and respiration of Rhizobium lupini cultivated in the conditions of different aeration, and bacteroids of this strain isolated from lupine nodules. In the anaerobic conditions, nitrate (10(-3) M) accepts electrons from the cytochrome system in suspensions of bacteroids and bacterial cells grown in the microaerophilic conditions (12 muM O2), but does not oxidize cytochromes of the cells cultivated in the aerobic conditions (240 muM 32). Nitrate (10(-3) M) oxidizes actively only the cytochrome system of the cells grown in the microaerophilic conditions. Nitrite inhibits oxygen uptake by suspension of the bacteroids and pure culture of the cells; its necessary concentrations and the mode of action depend on the conditions of cultivation. Nitrite, like cyanide, blocks the terminal step in the cytochrome chain of Rh. lupini. Some properties of the cytochrome system are similar in the bacteroids and the bacterial culture grown in the conditions of oxygen deficiency.