RESPIRATORY MECHANISMS IN FLEXIBACTERIACEAE .I. STUDIES ON TERMINAL OXIDASE SYSTEM OF LEUCOTHRIX MUCOR

Membrane fragments from the marine flexibacterium Leucothrix mucor can be obtained by disrupting the cells by sonication or high-pressure extrusion. Such preparations are active in the oxidation of NADH and succinate and are inhibited by antimycin A, HOQNO, cyanide, and CO. The antimycin inhibition can be bypassed by TMPD. NADH-oxidase is not inhibited by rotenone or amytal. The particles can also interact in oxidative activities with DPIP, PMS, ferricyanide, ascorbate, and mammalian cytochrome c. Low-temperature (-196 °) difference spectrophotometry of whole cells and particles reveals the presence of four absorption bands in the α region of cytochromes, the relative absorbencies of which are markedly affected by growth conditions of the cells. From observations on the steady-state level of reduction of these components in the presence of various substrates, reductants, and inhibitors, we propose that the sequence of electron carriers is: substrate→ B562→ C552(458)→ B558→ oxygen. The only CO-binding pigment present in this organism is photodissociable at room temperature but not at -196 ° and is spectroscopically similar to cytochrome o. We suggest that this pigment is the functional terminal oxidase in L. mucor and is equivalent to cytochrome B558. © 1968.