ABSTRACT
As a widespread phenomenon in nature, many species of motile bacteria exhibit a chemotactic response toward oxygen, sugars, amino acids, and various other inorganic and organic substances. In cases for which the bacterial population is very large and the number of cells per unit volume varies in a virtually continuous fashion through the medium, one can formulate a phenomenological theory for bacterial chemotaxis. The distribution of chemotactic cells and the varying concentration of the limiting attractant are governed by coupled partial differential equations. This chapter reviews the mathematical details of the phenomenological theory for bacterial chemotaxis. The chemotaxis of motile bacteria plays a key role in symbiotic associations of microorganisms in natural habitats, and the phenomenological theory for bacterial chemotaxis can be applied to illuminate certain quantitative aspects of these symbiotic associations. Oxygen-depleted, organically rich ponds, swamps, and other fresh water habitats provide natural ecosystems for large steady-state populations of methanobacteria.
