Nitric oxide complex of cytochrome c' in cells of denitrifying bacteria.

Electron paramagnetic resonance (EPR) spectra at 77K have been measured for the dried cells of three groups of chemoheterotrophic bacteria cultured in the presence of nitrate: I, denitrifying bacteria containing cytochrome c' (Alcaligenes sp. NCIB 11015, Achromobacter xylosoxidans GIFU 543); II, denitrifying bacteria in which cytochrome c' has not been found (Alcaligenes faecalis IAM 1015, Bacillus firmus NIAS 237, Pseudomonas stutzeri ATCC 17641); III, non-denitrifying bacterium containing cytochrome c' (A. xylosoxidans GIFU 1055). A characteristic three-line EPR signal was detected only in the dried cells of group I, and was assigned to NO-cytochrome c' complex. The probable physiological role of the cytochrome c' in denitrifying bacteria is discussed.