Experiments on Enzyme Induction in the Unicellular Green Alga Chlorella fusca

The ability of microorganisms to adapt their enzyme complement in response to varying growth conditions has been established since the early years of this century. The experiments reported here use the unicellular green alga, Chlorella fusca , in a study of the induction of the enzyme isocitrate lyase in response to the presence of acetate in the growth medium in a variety of growth conditions. These include variation in the light and aeration regimes, and the presence and absence of glucose. The experiments are essentially simple and do not employ sophisticated techniques. However, they do represent a different approach to conventional experiments on enzyme induction that, almost invariably, use the bacterium Escherichia coli as the test organism in a straightforward examination of the time course of induction of β -galactosidase in response to lactose. In addition to the “basic” experiment, a wide range of additional experiments are suggested based on the same general approach. This enables the generation of experimental data that are either relatively straightforward to interpret, or data that can tax an advanced student. The experiments outlined are suitable for a practical class of 3 h or can be extended to provide a project that might occupy a student, or group of students, for 10 or more 6-h practical sessions.