BIOENERGETIC ASPECTS OF AEROBIC GLUCOSE-METABOLISM OF ESCHERICHIA-COLI K-12 UNDER VARYING SPECIFIC GROWTH-RATES AND GLUCOSE CONCENTRATIONS

Abstract

An attempt was made to find a bioenergetical explanation for the differential effect of specific growth rate and glucose concentration on glucose metabolism of E. coli K-12 with the help of 2,4-dinitrophenol (DNP). The effect of DNP on biomass occurred only at high glucose concentrations. The presence of this uncoupler strongly stimulated glucose uptake rates and O2 uptake rates, but repressed severely Yg [molar growth yield per mole glucose] values. Increase in glucose concentration sharply decreased QO2. The amount of O2 required for maintenance was not affected by DNP, but Yo max [maximum growth yield per mole oxygen] values were much lower in the presence of DNP. The results are discussed and aerobic fermentation is probably caused by a severe reduction of site 1 of the respiratory chain region, whereas biomass formation is probably affected by repression of the terminal cytochrome a2. In comparing the effect of glucose on biomass formation at similar Qglucose levels in aerobic and anaerobic fermentation, repression occurred in both cases at glucose concentrations of 0.3% and above. Although the analyses of 15 enzymes established the metabolic differences, the repression of growth was common to both fermentation types.