CHARACTERIZATION OF 2 TERMINAL OXIDASES IN BACILLUS-BREVIS AND EFFICIENCY OF ENERGY-CONSERVATION OF THE RESPIRATORY-CHAIN

The respiratory chain of Bacillus brevis was analyzed. Resting cells s howed 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 interme diate between those of Bacillus subtilis (about 4), which predominantl y expresses cytochrome aa(3)-type quinol oxidase, and Bacillus stearot hermophilus (about 6), which has quinol-cytochrome c reductase plus ca a(3)-type cytochrome c oxidase, Measurement of respiration with variou s substrates, and its inhibition by cyanide suggested that aa(3)-type quinol oxidase and caa(3)-type cytochrome c oxidase operate simultaneo usly in the respiratory chain of B. brevis, Both terminal oxidases mer e isolated by solubilizing B. brevis membranes with Triton X-100, and fractionating the extract using DEAE-Fractgel and gel-filtration colum ns. The quinol oxidase (aa(3)) was composed of four subunits (57, 34, 23, and 15 kDa), like its counterpart of B. subtilis, while three subu nits (52, 34, and 22 kDa) were identified in the cytochrome c oxidase (caa(3)) preparation in B. stearothermophilus.