Sensitivity Analysis in Microbial Communities
A gnotobiotic aquatic microcosm, consisting of three species, including: bacteria, Escherichia coli; protozoa, Tetrahymena thermophila; and a primary producer, Euglena gracilis, was prepared, in which all species co-existed for over 130 days. Interactions among the species were analysed to clarify mechanisms involved in co-existence. The growth of T. thermophila depended on the number of E. coli, that is, T. thermophila grew when more than 106 E. coli cells per ml were present. No T. thermophila survived in a medium without other organisms. It, however, did grow in the presence of Eu. gracilis. As T. thermophila does not feed on Eu. gracilis, it is hypothesized that a metabolite of Eu. gracilis had a positive effect on growth of T. thermophila. Competition between E. coli and Eu. gracilis for proteose peptone in the medium was not observed. These interactions appeared to depend on successful co-existence of the three species. These results were confirmed by mathematical analysis, using parameter sensitivity of a dynamic model.
KeywordsMicrobial Community Mixed Culture Steady State Level Parameter Sensitivity Population Change
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