Simulation of a bacterial population structure in continuous cultivation by a dissociation process: An application to Rhodococcus rubropertinctus

An attempt is made to give a quantitative estimation of a possible contribution of the dissociation process in the formation of the heterogeneous population structure for the Rhodococcus rubropertinctus (Micobacterium lacticolum) in continuous cultivation. This estimation is realised with the help of a constructed mathematical model of the process. The model equations obtained describe particular biomass changes for R-, S- and M-dissociants and changes for substrate (glucose) concentration within the chemostate in continuous cultivation. Next, contributions to dissociant biomass changes were taken into account: (1) cell reproduction (each dissociant has its own specific growth rate depending on the substrate concentration), (2) cell outflow (in proportion to dissociant biomass) and (3) dissociation (dissociant genotype change during reproduction occurs for each dissociant with its own specific frequency). It is determined that if substrate growth constants are equal the rapidly growing dissociants (possessing maximal μ_max) outs the rest of them, and the greater the speed of the flow the less the time to reach a steady-state distribution of the dissociant biomasses. But, at the same time the slowly growing dissociant can become dominant in the population if it has a lower substrate growth constant.