1997 Volume 122 Issue 5 Pages 969-976
The respiratory chain of Bacillus brevis was analyzed. Resting cells showed an H+/O ratio of 4.8-5.2 (5.01±0.26), when measured using an oxygen pulse method with endogenous substrates. This value is intermediate between those of Bacillus subtilis (about 4), which predominantly expresses cytochrome aa3-type quinol oxidase, and Bacillus stearothermophilus (about 6), which has quinol-cytochrome c reductase plus caa3-type cytochrome c oxidase. Measurement of respiration with various substrates, and its inhibition by cyanide suggested that aa3-type quinol oxidase and caa3-type cytochrome c oxidase operate simultaneously in the respiratory chain of B. brevis. Both terminal oxidases were isolated by solubilizing B. brevis membranes with Triton X- 100, and fractionating the extract using DEAE-Fractgel and gel-filtration columns. The quinol oxidase (aa3) was composed of four subunits (57, 34, 23, and 15 kDa), like its counterpart of B. subtilis, while three subunits (52, 34, and 22 kDa) were identified in the cytochrome c oxidase (caa3) preparation in B. stearothermophilus.
