Theoretical and experimental evidence of extinction and coexistence of killer and sensitive strains of yeast grown as a mixed culture in water.

Theoretical and experimental evidences of extinction and coexistence during batch interaction of killer and sensitive strains of Saccharomyces cerevisiae grown as a mixed culture in pure water are provided. The experimental results show that in the limited nutrient conditions of growth in pure water, the killer yeast is subject to extinction when the initial concentration ratio of killer to sensitive yeast is 1:100. However, if the initial concentration ratio of killer to sensitive yeast is 1:1, both strains coexist. Substantial damped oscillations are associated with the growth process in the mixed culture. A new theoretical model that was originally developed for recovering the growth of single species in isolation is extended and applied to two species competing over a common ecological niche. The solutions of the model are shown to recover all the qualitative features captured in the experiments.