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growth and nutrition of bacteria

Growth and Nutrition of Bacteria

Bacteria divided by binary fission.

Bacterial Growth

Bacterial growth may be considered two level;

1. Increase in size of individual cell.

2. Increase in number of cells.

Bacterial Growth Curves

When bacteria is inoculated into suitable culture medium and incubated growth is occured.

All growth phases are represented on graph Known as growth curve.

Growth curve has four phases;

1st phase (lag phase)

2nd phase (log phase)

3rd phase (stationary phase)

4th phase (Phase of decline)

1. Lag phase 

After inoculation of culture medium, multiplication doesn't begin immediately.

The period between inoculation and beginning of multiplication known as lag phase.

Lag phase is the phase of intense metabolic activity.

Initial phase characterized by cellular activity but not growth.


2. Log phase or exponential phase

Cell division starts and their numbers increase all their maximum rate.

This also known as growth phase.

The time required for bacterium to give rise to two daughter cells under optimum conditions is known as generation time.

3. Stationary Phase

After log phase, bacterial growth almost completely due to exhaustion of nutrient. 

The viable count remains stationary as equilibrium exists between the dying cells and newly formed cells.

Sporulation occurs at this phase.

4. Phase of decline

After period of stationary phase, bacterial population decreases due to death of cells.

The decline phase starts due to exhaustion of nutrient and toxic accumulation.

Cell death may also be caused due due by autolytic enzyme.

But not complete death of bacteria occur at this phase.

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