NAPHTHOQUINONE INTERMEDIATE IN THE RESPIRATION OF BACILLUS STEAROTHERMOPHILUS.

Downey, R. J. (U.S. Department of Agriculture, Washington, D.C.). Naphthoquinone intermediate in the respiration of Bacillus stearothermophilus. J. Bacteriol. 84:953-960. 1962.-A vitamin K-like naphthoquinone has been isolated from Bacillus stearothermophilus. The compound was susceptible to light (360 mmu) and can be extracted from electron-transport particles with organic solvents. The reduced diphosphopyridine nucleotide (DPNH) oxidase and DPNH-cytochrome c reductase activities in such particles were restored to original levels by the addition of the extracted intermediate, by vitamin K(1), or by menadione. Phosphorylation coupled to the oxidation of malate was restored by addition of the isolated naphthoquinone. Discrepancies in the rate of succinate oxidase and succinate-naphthoquinone reductase activities suggested the intermediate functions in a collateral pathway in the succinate oxidase system of this organism. Anaerobic and aerobic cultivation of the microorganism produced no detectible differences in the character of the intermediate. Reduction of nitrate by the thermophile was not completely dependent upon the naphthoquinone but was significantly stimulated in its presence. No evidence was obtained for the existence of a mixed quinone system in the bacillus.