MODELING THE INDIVIDUAL GROWTH OF TETRAHYMENA SP AND ITS POPULATION CONSEQUENCES

Three types of mathematical growth models are presented to describe th e individual growth of the ciliate Tetrahymena sp. feeding on the bact erium Pseudomonas fluorescens. Both organisms were isolated from a dom estic waste-water treatment plant. Growth of individual ciliates and t he consequences for the whole population are considered. Experimental data, obtained by following the individual ciliate during its lifespan from cell division to cell division, are used for parameter estimatio ns. Differences between growth models for individuals turn out to have little effect on the specific population growth rate and the mean cel l volume. In case of exponential growth of individuals the unstructure d and structured population models are equivalent, even in time-varian t environments. This knowledge can be applied in the stability analysi s of food chains or forced systems. The results obtained facilitates q uantification of protozoa biomass as a function of bacterial biomass i n chemostats. More specifically, it highlights the dynamic behaviour o f bacteria and protozoa in waste-water treatment plants.