Alkaline growth pH-dependent increase of respiratory and NADH-oxidation activities of the facultatively alkalophilic strain Bacillus lentus C-125

Respiration of a facultative alkaliphile, Bacillus lentus C-125, was increased around alkaline pH near the upper pH-limit for growth of the organism. O-2-Uptake rates of the cells grown in a complex medium at pH 7-9 and 9.5-10 were 0.98-1.4 and 2.4 mu mol O atom/min/mg cell protein, respectively. Membrane vesicles from the cells grown at pH 7-9 and 9.9 incorporated O-2 at rates of 1.1-1.4 and 2.5 mu mol O atom/min/mg envelope protein, respectively, using exogenous NADH as an electron donor. In the presence of menadione as an exogenous electron acceptor, the membrane vesicles from the cells grown at pH 7-8.5 and 9.9 oxidized NADH at rates of 1.4-1.7 and 6.3 mu mol NADH/min/mg envelope protein, respectively. Levels of respiratory and NADH-oxidation activities of the organism are dependent on the growth pH, and higher than those reported previously in alkaliphilic Bacillus spp.