Electron Transporting Components Participating in Nitrate and Oxygen Respirations from a Halotolerant Micrococcus*

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Abstract
The cells were ground with alumina in 0.05 [image] phosphate buffer (pH 7.0), and submitted to differential centrifugations to separate P2 (precipitates at 20,000 x g), P10 (precipitates at 105,000 x g) and S10 (soluble supernatant) fractions. P2 and P10 possessed the activities of cytochrome C554 (cyt. c554)-reductase with presence of succinate, reduced diphosphopyridine-nucleotide (DPNH) and formate, nitrate reductase, and cytochrome oxidase, and contained cyt. b560, whereas S10 showed only cyt. C554-DPNH reductase activity and a trace activity of other enzymes. P10 was treated vith 0.5%Na deoxycholate, 0.05% snake venom and 0.1% pancreatic lipase at pH 8.0 simultaneously by homogenization and incubation for 16 hrs. at 4[degree]C. The centrifuged supernatant was enriched by cytochrome oxidase, nitrate reductase and brown protein. These were separated by DEAE-cellulose column chromatography. With the use of P10, reoxidation of reduced cyt. C554 by nitrate proceeded at a rage higher than that by 02. The following electron transporting system in the bacterial cells is proposed: from an electron donor we proceed to a flavoprotein then to cytochrome b560 and then to cytochrome C554. From that point, one route proceeds to cytochrome c551 to cytochrome oxidase and then to O2. Another route goes from brown protein to nitrate reductase and then to nitrate.