The membrane of the bacterium oxidized NADH maximally at pH 7.5, and ATPase bound to the membrane exhibited maximum activity at pH

An alkalophilic bacterium belonging to the genus Bacillus was isolated from an indigo ball. The bacterium exhibited a maximum growth rate at pH 10.0 to 10.5. The incorporation of 14C-labelled amino acids or [14C]uracil,uptake of 14C-labelled aamino isobutyric acid into the bacterium and oxygen consumption of the bacterium with amino acids as substrates were all maximum at pH 9.0 to 10.5. The uptake of [U-14C]glucose into the organism and oxygen consumption with carbohydrates, on the other hand, showed little variation of rate in the pH 8 to 10 region. The oxygen consumption of intact bacteria or protoplasts in culture medium was maximum at pH 10. The membrane of the bacterium oxidized NADH maximally at pH 7.5, and ATPase bound to the membrane exhibited maximum activity at pH 7. L-Lactate, L-alanine and malate dehydrogenases in the soluble fraction exhibited maximum activities at pH 7.4 to 8.4. The alkalophilic property of the bacterium may be due to the behaviour of the membrane towards charged substances admitted into the organisms.