Set 5: Reproduction & Population Growth Curves

What is binary fission?

Binary fission is the process by which one cell divides into two

What are the three main steps involved in the process of binary fission?

1. Elongation

2. Replication

3. Separation

What happens in Elongation in the Binary fission?

Parent cell grows.

What happens in Replication in the Binary fission?

Chromosome replicates and copies separate.

What happens in Separation in the Binary fission?

A septum (cell wall) forms, dividing the cell (septation/cytokinesis).

Define "generation time" (or doubling time)

Generation time is the time required for a complete cycle of binary fission (for one cell to become two).

How does ‘“generation time'“ differ between Mycobacterium leprae and Staphylococcus aureus?

• M. leprae: Very slow (10-30 days).

• S. aureus: Very fast (20-30 minutes).

Describe what is happening to the microbial population during the Lag phase?

Cells are synthesizing new components and adjusting to the new medium; population size does not increase significantly.

Describe what is happening to the microbial population during the Log phase?

Cells are growing and dividing at their maximum rate; population doubles at regular intervals.

What are three possible reasons a microbial culture enters the Stationary Phase?

1. Nutrient limitation.

2. Limited oxygen availability.

3. Toxic waste accumulation.

What happens during the Death Phase?

Viable cell numbers decline at a constant rate as conditions become too harmful.

What is the "Long Term Stationary Phase"?

After initial death, the population may remain constant for months or years, with some cells genetically adapting to use nutrients from dead cells. Some cells may enter a "viable but not culturable" (VNC) state.