Association for Biology Laboratory Education

Simulating Bacterial Chemostat Growth as an Introduction to Rate Modeling with Calculus
    

Pryce L. Haddix and Luke Smith

Advances in Biology Laboratory Education, 2024, Volume 44

https://doi.org/10.37590/able.v44.art9

Supplemental Materials: https://doi.org/10.37590/able.v44.sup9

Abstract

The bacterial chemostat is a device which enables experimenter control over population growth rate by restricting access to nutrients. Replacement of a small volume of fully-grown, nutrient-starved culture with an equal volume of sterile nutrient medium constitutes a continuous dilution process enabling new cell production at the rate of culture replacement. Population growth rate is directly proportional to both culture replacement rate and cell concentration but is inversely proportional to culture volume. In order to illustrate the utility of rate modeling for biology, this work describes the theoretical basis of chemostat growth in terms of both algebra and calculus. We also describe a simple and non-biohazardous dye dilution laboratory activity that illustrates the modeling. The laboratory activity may be implemented in as little as one hour as a demonstration or student activity. This activity is appropriate for an undergraduate junior-level microbiology laboratory or as a first-semester calculus demonstration.

Keywords:  mathematical modeling; chemostat; interdisciplinary connections

University of California, San Diego (2023)