THE RELATION OF PROTON MOTIVE FORCE, ADENYLATE ENERGY-CHARGE AND PHOSPHORYLATION POTENTIAL TO THE SPECIFIC GROWTH-RATE AND EFFICIENCY OF ENERGY TRANSDUCTION IN BACILLUS-LICHENIFORMIS UNDER AEROBIC GROWTH-CONDITIONS

The magnitude of the proton motive force (DELTAp) and its constituents, the electrical (DELTAPSI) and chemical potential (-ZDELTApH), were established for chemostat cultures of a protease-producing, relaxed (rel-) variant and a not protease-producing, stringent (rel+) variant of an industrial strain of Bacillus licheniformis (respectively referred to as the A- and the B-type). For both types, an inverse relation of DELTAp with the specific growth rate mu was found. The calculated intracellular pH (pH(in)) was not constant but inversely related to mu. This change in pH(in) might be related to regulatory functions of metabolism but a regulatory role for pH(in) itself could not be envisaged. Measurement of the adenylate energy charge (EC) showed a direct relation with mu for glucose-limited chemostat cultures; in nitrogen-limited chemostat cultures, the EC showed an approximately constant value at low mu and an increased value at higher mu. For both limitations, the ATP/ADP ratio was directly related to mu. The phosphorylation potential (DELTAG'p) was invariant with mu. From the values for DELTAG'p and DELTAp, a variable -->H+/ATP-stoichiometry was inferred: -->H+/ATP= 1.83 + 0.52mu, so that at a given -->H+/O-ratio of four (4), the apparent P/O-ratio (inferred from regression analysis) showed a decline of 2.16 to 1.87 for mu = 0 to mu(max) (we discuss how more than half of this decline will be independent of any change in internal cell-volume). We propose that the constancy of DELTAG'p and the decrease in the efficiency of energy-conservation (P/O-value) with increasing mu are a way in which the cells try to cope with an apparent less than perfect coordination between anabolism and catabolism to keep up the highest possible mu with a minimum loss of growth-efficiency. Protease production in nitrogen-limited cultures as compared to glucose-limited cultures, and the difference between the A- and B-type, could not be explained by a different energy-status of the cells.