Suppose you inoculate three flasks of minimal salts broth with E. coli. Flask A contains
glucose. Flask B contains glucose and lactose. Flask C contains lactose. After a few hours of incubation, you test the flasks for the presence of ß-galactosidase. Which flask(s) do you predict will have this enzyme?
a. A
b. B
c. C
d. A and B
e. B and C

Verified step by step guidance

1. Understand that ß-galactosidase is an enzyme that breaks down lactose into glucose and galactose.
2. Recall that E. coli produces ß-galactosidase only when lactose is present, as it is part of the lac operon system.
3. Consider Flask A, which contains only glucose. E. coli will not produce ß-galactosidase because there is no lactose to induce the enzyme's production.
4. Consider Flask B, which contains both glucose and lactose. Initially, E. coli will prefer glucose, but once glucose is depleted, lactose will induce ß-galactosidase production.
5. Consider Flask C, which contains only lactose. E. coli will produce ß-galactosidase to metabolize lactose from the start.

Key Concepts

Metabolism of E. coli

E. coli is a versatile bacterium capable of utilizing various carbon sources for energy. It can metabolize glucose through glycolysis, while lactose requires the enzyme ß-galactosidase to break it down into glucose and galactose. Understanding how E. coli metabolizes these sugars is crucial for predicting enzyme production in different growth conditions.

Inducible Enzymes

Inducible enzymes are produced in response to the presence of specific substrates. In the case of lactose, ß-galactosidase is an inducible enzyme that is synthesized when lactose is available, allowing E. coli to utilize it as a carbon source. This concept is essential for predicting which flasks will show enzyme activity based on their contents.

Lactose Utilization in Bacteria

Lactose utilization in bacteria involves the transport of lactose into the cell and its subsequent hydrolysis by ß-galactosidase. Flask B, containing both glucose and lactose, will likely show ß-galactosidase activity due to the presence of lactose, while Flask C will also show activity as it contains only lactose. Flask A, containing only glucose, will not produce this enzyme.