Coexistence of two asexual strains on a single resource.

A stable equilibrium was obtained for two F(-) strains of Escherichia coli in a glucose minimal medium. This equilibrium cannot readily be explained by traditional models of population genetics and apparently violates some forms of the ecological principle of competition exclusion. A mechanism involving an inverse relationship between the growth rates of these strains at the exponential and "stationary" phases is suggested as a possible explanation for the observed stable equilibrium.