Actual and potential rates of substrate oxidation and product formation in continuous cultures ofChromatium vinosum

Abstract

Kinetics of electron-donor oxidation, storage-polymer formation and growth were studied in continuous cultures ofChromatium under conditions of balanced growth as well as during transient states.

Under steady-state conditions, glycogen was accumulated at all dilution rates. This observation is consistent with previously postulated ideas about an ineffective glycogen-synthesis regulation.

Upon perturbing the steady states, brought about by injection of extra sulfide into steady-state cultures, the following phenomena were observed immediately, irrespective of the dilution rate: the specific rate of sulfide oxidation increased to the value found in batch cultures, the sulfur-oxidation rate was decreased, the specific glycogen-synthesis rate increased, the increment being higher the lower the dilution rate, but an increase in the specific growth rate, if any, was below the limit of detection. The inverse relationship between the specific rates of glycogen synthesis and growth after removing the substrate limitation is to be explained by a shortage of intermediates, rather than by a growth-rate dependent intrinsic glycogen-synthesis limitation, because upon complete inhibition of growth a further increase in the rate of glycogen synthesis was observed. Essayed in this way, identical glycogen-synthesis rates were found at all dilution rates.

Competitive advantages of such an apparently not adapted metabolism in environments with diurnal fluctuations in substrate concentrations are discussed.