Competition between plasmid-bearing and plasmid-free organisms in a chemostat

In this paper, we consider a model of competition between plasmid-bearing and plasmid-free organisms in the chemostat, where the yield coefficients and growth rates are assumed to be general functions of the nutrient concentration. We give a characterization of the outcome of this competition in terms of the relevant parameters. Conditions of the existence and local stability of the rest points are obtained, and the global asymptotic behavior of the solutions is analyzed. In contrast to the corresponding model with constant yields rate, it is demonstrated that the variability of the yield coefficient may lead to oscillatory coexistence of plasmid-bearing and plasmid-free organisms in continuous culture.