Question

Explain a batch growth curve under optimal conditions and an example of an inducible operon that is a model.

Answer 1

In a batch growth curve there are four phase-

1-Lag Phase - bacteria are adopting to environment (new medium),absorb nutrients, cell synthesizing new components (enzyme), prepared for cell division, this phase varies in length.
there is no increase in bacterial number in this phase.

2-Log phase (logarithmic growth phase)-Rapid multiplication occur causing very high increase in the number of bacteria.

3-stationary phase-total number of viable cell remains constant, In this phase nutrients in the media decrease and the toxic waste resulting from bacterial metabolism increase which cause the slow multiplication of cell.

4- death phase- cell dying usually at exponential rate due to the lack of nutrients and accumulation of toxic waste.

The lac operon of E. coli is an example of an inducible operon. The lac operon contains a promoter, terminator, an operator that control the transcription and also 3 structural genes—lacZ, lacY, and lacA which coding for enzyme in hydrolysis and metabolism of lactose. It is usually off but can be turned on in the presence of lactose.