THE DYNAMICAL ANALOGY BETWEEN MICROBIAL-GROWTH ON MIXTURES OF SUBSTRATES AND POPULATION-GROWTH OF COMPETING SPECIES

There is a similarity between the metabolic dynamics of a microbial sp ecies growing on a mixture of two substrates and the dynamics of growt h of two competing populations. Specifically, the enzymes catalyzing t he uptake and catabolism of substrates exhibit phenomena analogous to extinction and coexistence. ''Extinction'' of the enzymes associated w ith one of the substrates results in sequential utilization of the sub strates (diauxie) (Monod, 1942). ''Coexistence'' of the enzymes associ ated with the substrates results in simultaneous utilization of the su bstrates (Egli, 1995). Here, we formulate a simple model that shows th e basis for this dynamical similarity: The equations describing the ev olution of the enzyme levels are dynamical analogs of the Lotka-Volter ra model for two competing species. The analogy suggests ways of captu ring the experimentally observed preculture-dependent growth patterns, i.e., growth patterns that vary depending on the physiological state of the preculture. (C) 1998 John Wiley & Sons, Inc.