On the coexistence of three microbial populations competing for two complementary substrates in configurations of interconnected chemostats

We examine the question of coexistence of three microbial populations compe ting for two complementary rate-limiting substrates in configurations of in terconnected chemostats. It is known that coexistence of two populations co mpeting for two rate-limiting substrates is possible in a single chemostat, but coexistence is not possible when three populations are involved. We ex amine whether coexistence of three populations becomes possible by consider ing configurations of two or three interconnected chemostats, thus allowing for effects of spatial heterogeneity. Computational analysis of the model equations indicates that in the case of two chemostats coexistence is possi ble only for specific discrete parameter values where the system is structu rally unstable and therefore the coexistence state is not practically attai nable, whereas in the case of three chemostats coexistence is possible for a whole range of parameter values where the system is structurally stable a nd therefore the coexistence state can be realized in practice. (C) 1998 Pu blished by Elsevier Science Inc. All rights reserved.