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Electron Transport System Associated with Membranes of Bacillus cereus During Vegetative Growth and Sporulation

¹ Department of Biology, Syracuse University, Syracuse, New York 13210

ABSTRACT

Membranes isolated from Bacillus cereus ATCC 4342 during vegetative growth and during sporulation contained cytochromes b, c and a + a₃ as well as flavoprotein as determined from reduced-minus-oxidized difference spectra. Although there appeared to be no qualitative change in the cytochromes, there was a significant increase in the amount of cytochromes associated with membranes isolated from sporulating cells. Succinate and nicotinamide adenine dinucleotide (reduced form) (NADH) reduced the same cytochromes indicating similar pathways of electron transport. The electron transport inhibitors—cyanide, azide, 2-heptyl-4-hydroxyquinoline-N-oxide, dicumarol and atebrine—were examined for their effect on succinate oxidase (succinate: [O₂] oxidoreductase) and NADH oxidase (NADH: [O₂] oxidoreductase). NADH oxidase associated with vegetative cell membranes was less sensitive to certain inhibitors than was succinate oxidase, suggesting a branched electron transport pathway for NADH oxidation. In addition to electrons being passed to O₂ through a quinone-cytochrome chain, it appears that these intermediate carriers can be bypassed such that O₂ is reduced by electrons mediated by NADH dehydrogenase. Both oxidases associated with sporulating cell membranes were inhibited to a lesser degree than were the oxidases associated with vegetative cell membranes.