Question

What are the stages of a batch culture growth curve? Make sure you explain in full what is going on in each stage and why

Answer 1

1. Lag phase:

• the organism like bacteria become adapted to the culture media and new nutrients.
• Precursor molecules required for growth are synthesized. The synthesis proteins, nucleic acids (DNA and RNA) takes place before initiation of cell division.
• This phase requires some time to proceed.
• There is no such increase in number of cell as compared with initial number.

2. Log phase:

• It is also known as Exponential phase
• Here microbes are fully adopted to media condition.
• Proteins/enzymes are synthesized.
• Cells starts to multiply. Growth rate is at maximum
• rate of division is much more faster than rate of death. therefore number of cells in media increases very fast.
• Time period for this phase last longer as compared with other phases. i.e. few hours to days depending upon organism being cultured.
• Also metabolic waste products starts to produce in this phase.

3. Stationary phase:

• Metabolic wastes are concentrated, so the pH of the medium changes.
• Nutrients in the medium are completely utilized
• As a result, rate of cell division is nearly stopped. Rate of cell division is equal to the rate of cell death.
• Thus growth rate remains stationary or steady.

4. Death phase:

• Toxic metabolic waste makes media unsuitable for growth of cells.
• Number of cell decreases exponentially due to rapid cell death.
• Only few cells will survive longer in this phase due to mutations occured in them.