GROWTH CYCLE OF BACTERIA

Bacteria reproduce by Binary fission, a process by which a parent cell divides in two progeny cells. As one cell gives rise to two daughter cells, bacteria is said to undergo logarithmic (exponential growth).

The doubling time for bacteria ranging from as little as 20 minute (E.coli) to more than 24 hour (Mycobacterium Tuberculosis). The doubling time varies not only with species but also with the amount of nutrients, pH, temperature and so many other factors. The growth cycle of bacteria has four phases. If a small number of bacteria are inoculated into a liquid nutrient medium and bacterial count is made at frequent intervals, the typical phases of the standard growth curve can be made.

Standard growth has four phases.

1. LAG Phase:

In this phase vigorous metabolic activity occurs but no division takes place.

2. Logarithmic Phase:

In this phase rapid cell division takes place.

3. Stationary Phase:

In this phase depletion of nutrients or production of toxic metabolic substances cause growth to slow until the number of new cell produce balances the cells that die.

4. Decline Phase:

In this phase there is marked death of bacterium and the number of viable bacteria declines.