Influence of sulfooxyanions on oxygen uptake, carbon dioxide fixation, and cytochrome reduction in Nitrobacter agilis

Oxygen uptake coupled with nitrite oxidation by washed cell suspensions was not influenced by persulfate or tetrathionate. Carbon dioxide fixation was insensitive to tetrathionate, and in fact, an enhancement by tetrathionate was observed. Persulfate inhibited the fixation of carbon dioxide only at a high concentration (17 mM S2O2−8). Cytochrome reduction in washed cells of Nitrobacter agilis was demonstrated in the presence and absence of sulfooxyanions. Cytochrome aa3 and cytochrome a1 (α-peak at 590 nm) were sensitive to sulfooxyanions (sulfite, thiosulfate, metabisulfite, dithionate, persulfate, trithionate, and tetrathionate), whereas cytochrome c (β-peak at 520 nm) was insensitive to test ions. All sulfooxyanions inhibited the reduction of cytochrome a1 (γ-peak at 438 nm). This inhibition decreased when the concentration of sulfooxyanions was increased to 17 mM. The reduction of cytochrome c at 550 nm (α-peak) was blocked by the test ions and the inhibition of cytochrome c at 415 nm (γ-peak) was also apparent. Complete inhibition of cytochrome c (γ-peak) was observed in the presence of 17 mM persulfate.