Chemostats

Abstract

A chemostat is an experimental chamber (Fig. 14.1) in which the dynamics of small, usually asexually reproducing organisms are studied under controlled laboratory conditions. While it is not a requirement, chemostats are typically maintained in a steady-state condition. A steady-state chemostat consists of a growth chamber into which a constant concentration of nutrients are pumped at a constant rate. Organisms are introduced into the chamber and allowed to take up nutrients and grow. Both the growth medium and the microorganisms are removed from the chamber at a constant rate in order to maintain a constant volume. The purpose of this arrangement is to permit the microorganisms to grow in constant abiotic (nutrient) conditions. These systems have applications in research laboratories for physiological studies, in industry as a method to produce large quantities of chemical by-products useful in research and medicine (e.g., enzymes), and in sewage treatment plants. Chemostats are not common in nature, but they are sometimes closely approximated in aquatic upwelling systems such as those located off the western coast of South America. The biological questions that models of chemostats can address include: (1) What is the effect of temporal variability on the outcome of competition? Is it likely that high species diversity in ecological communities is maintained by temporal variability? (2) Can chaos arise in simple predator-prey models?