Ecology and toxicology of a Tetrahymena pyriformis - Escherichia coli community : a modeling study with an individual based approach

The dynamics of a microbial community Tetrahymena pyriformis - Escherichia coliin a batch culture is investigated by means of a mathematical model with an individual based approach. It is shown that utilization of an individual - based approach as a modeling technique leads to expansion of the coexistence domain of bacteria in the presence of ciliates and, in general, improves agreement of theoretical results with experimental data. The influence of processes that might interfere with feeding of both populations and contribute to community coexistence such as accumulation of E. coli sized particles and accumulation of E. coli toxic metabolites is also evaluated. Investigation of the possible effects of nonpolar narcotics on the ciliate - bacterial community is contained in the second part of the study. The basis for the exposure model is passive diffusion. It is shown that effects of toxicants can be stimulative for more resistant species, bacteria, while their predators, more susceptible, are adversely affected. Moreover, it is shown that in a closed, batch system presence of nonviable organic material modifies bioavailability of a toxicant and allows for existence of species above levels that would cause mortality in a continuous culture.