The respiratory system of Rhizobium phaseoli CFN42 in free-living cultures was studied. Cytochromes b, c, o and aa3 were found in fast growing cells cultured under forced aeration. Stationary aerobic cells, and semianaerobically grown cells showed decreased levels of cytochromes c, aa3 and o, concomitant with a significant increase of b type cytochromes and the synthesis of a new cytochrome, tentatively identified as cytochrome d. Cell membranes with the highest content of cytochrome d (semianaerobically grown cells) showed the highest respiratory activities with NADH, succinate, malate or ascorbate-TMPD (N,N,N′,N′-tetramethyl p-phenylendiamine). In the presence of either of the above electron donors, cytochrome d was clearly reduced. NADH dependent respiration in membranes of fast growing cells (no cytochrome d detected) was abolished by 25 μM KCN. This inhibitor concentration caused only 15–20% inhibition in membranes of semianaerobically grown cells (cyt d present). Moreover, in the presence of 1–5 mM KCN, the oxidation of cyt d and a b type cytochromes was spectrally detected. It is suggested that cyt d is a functional cytochrome in the respiratory system of free-living Rhizobia, probably acting as terminal oxidase.
Cytochrome d in Rhizobium phaseoli
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ApplebyCA (1969) a) Electron transport system of Rhizobium japonicum. I. Haemoproteins, P-450, other CO-reactive pigments, cytochromes and oxidases in bacteroids from N2-fixing root nodules. Biochim Biophys Acta 172:71–87CrossRefGoogle Scholar
AuDCT, LorenceRM, GennisRB (1985) Isolation and characterization of an Escherichia coli mutant lacking the cytochrome o terminal oxidase. J Bacteriol 161:123–127PubMedPubMedCentralGoogle Scholar
BergersenFJ, TurnerGL (1980) Properties of terminal oxidases system of bacteroids from root nodules of soybean and cow pea and of N2-fixing bacteria grown in continuous culture. J Gen Microbiol 11:235–252Google Scholar
LorenceR, KolandJG, GennisRB (1986) Coulometric and spectroscopic analysis of the purified cytochrome d complex of Escherichia coli: Evidence for the identification of “cytochrome a1” as cytochrome b595. Biochemistry 25:2314–2321CrossRefGoogle Scholar
MarkwellMAK, HaasSM, TolbertNE, BieberLL (1981) Protein determination in membrane and lipoprotein samples: manual and automated procedures. Methods Enzymol 72:296–303CrossRefGoogle Scholar