The strength of interspecies interaction in a microbial community determines its susceptibility to invasion
Fig 4
Lotka–Volterra interspecific competition model corroborates the link between interspecific competition and invasion success.
Outcomes based on a three-species Lotka–Volterra interspecific competition model that was extended to include killing by toxin (Materials and methods). In this model, the strength of interspecies interactions and the degree of ecological specialization are varied by adjusting the two-way competition coefficients. Specifically, the effect of S. Typhimurium on the growth of susceptible E. coli (representing the strength of interspecies interaction) and colicin-producing E. coli (representing ecological specialization) is modified by changing the competition coefficient aES and aCS, respectively. The effect of colicin-producing E. coli on the growth of the susceptible E. coli, due to competition for resources, is varied by changing aEC (represented as different colors in the figure). X-axis represents the strength of interspecies interaction and is calculated as the ratio between aES/aEE (Materials and methods). The selection coefficient represents the outcome of competition between the colicin-producing E. coli and susceptible E. coli in 3 species communities computed by numerically solving the model and is the measure of the invasion rate of the colicin-producing E. coli. A dependence of this invasion rate on the strength of interspecies interaction and ecological specialization is observed.