[Study of the mechanism of the effect of extracellular pH on the synthesis of the oxidative complex (cytochrome a+a3) of Bacillus coagulans: relationship to the "glucose effect" and role of excreted coproporphyrin III (author's transl)].

During the "respiratory adaptation" of Bacillus coagulans, it was possible to dissociate the kinetics of cytochrome a and a3 synthesis with carbon monoxide. The synthesis of cytochrome a3 is preferentially repressed when the pH of the incubation medium is pH 6.5 instead of pH 5.5. However, though the total synthesis of tetrapyrrole compounds is the same at both pH values, the excretion of coproporphyrin III is much increased at pH 6.5. Bacillus coagulans, sensitive to the "glucose effect", shows the "pH effect" only in the presence of high glucose concentrations. The repression of the oxidase complex synthesis by a slight increase of the extracellular pH appears directly related to the increase of the extracellular coproporphyrin III.