Effects of attachment of bacteria to chemostat walls in a microbial predator-prey relationship.

Mixed cultures of the protozoan Tetrahymena pyriformis and the bacterium Escherichia coli were propagated in chemostats fed with glucose and minimal mineral salts medium. The interior surfaces of some chemostats were treated with a silicone compound but those of other chemostats were not. Data obtained showed that bacteria but not protozoans were attached strongly to the walls of the chemostats, that silicone treatment reduced the density of the attached bacteria by two orders of magnitude or more, and that the presence of the attached bacteria had significant effects on the dynamics of the microbial predator-prey system. Attempts were made to simulate the data by various mathematical models. It was found that a model based on combination of the Topiwala-Hamer model for wall attachment and a multiple saturation model for growth of the protozoans on the bacteria gave a reasonable fit of all the data.