Bacterial Growth Curve

What happens during the lag phase in bacterial growth?

Cells adjust to new environment, synthesize enzymes, but do not divide yet.

Why is there no increase in population during the lag phase?

Cells are adapting and producing enzymes needed for new nutrient sources.

Example of enzyme activity during lag phase?

Cells in lactose medium produce lactose transport proteins and lactase.

What characterizes the log (exponential) phase?

Rapid cell division, exponential population growth, high DNA/protein synthesis.

Why is log phase ideal for industrial production?

Cells are metabolically most active and productive.

When are bacteria most vulnerable to antibiotics?

During the log phase.

What causes the stationary phase?

Nutrient depletion, oxygen scarcity, and waste buildup.

What is the growth pattern in the stationary phase?

Growth rate equals death rate; population size remains constant.

Name two starvation responses during stationary phase.

Endospore formation and production of starvation proteins.

How is stationary phase delayed in industry?

Using a chemostat to remove waste and add fresh nutrients.

What marks the death phase of bacterial growth?

Death rate exceeds growth rate due to toxic waste and lack of nutrients.

Do all cells die during the death phase?

No, some survive by forming endospores.

What is batch culture?

A closed system with no addition or removal of nutrients after inoculation.

What growth phases occur in batch culture?

Lag → Log → Stationary → Death

How is growth measured in batch culture?

Using Optical Density (OD) or Log CFU/ml.

How can growth rate be increased under ideal conditions?

By increasing temperature within the microbe’s tolerance range.

What limits growth under non-ideal conditions?

Limiting factors like nutrients, oxygen, pH, and salinity.

How can growth rate be optimized in environmental conditions?

Identify and adjust limiting factors or use different microbes/substrates.