Learn about the growth of bacteria and it's steps. How they grow up .

1. Bsc nursing 1 year
Microbiology
Unit :- 2 (bacterial growth
curve)
BY :- PRAGYA TIWARI

2. Bacterial growth curve :-
 When organism are cultured in appreciate fluid media, their would be increased
in size of the bacteria without any multiplication for some time (lag).
 This is followed by multiplication and increase in no. Of bacterial to the extent
that media look turbid (cloudy, opaque) to the naked eyes. (Log phase) .
 After sometim growth rate become stationary and later on decline.
 Counting of bacteria at different periods after inoculation and then events of
sequences are represented on a high graph which is called growth curve.

4. Lag phase :-
 It has short duration (1-40hrs), During this phase :-
1. Increase in size of cell.
2. Increase in metabolic rate.
3. Adaptation to new environment and necessary enzymes plus intermediate metabolites are build up for
multiplication to proceed.
The length of the lag phase depends upon the :-
 Type of bacteria.
 Better the medium, shorter the lag phase.
 The phase of culture from which inoculation is taken.
 Size of inoculum.
 Envirnment factor like :- temp.

5. Stationary phase :-
 After sometime (few hrs to few days) q stage comes when rate of multiplication
and death becomes all most equal. (Death rate and birth rate become equal).
1. It may be due to depletion of nutrition.
2. Accumulation of toxic products.
3. Sporulation may occur during this phase.

6. Log phase :-
 It’s duration is 8 hrs. In log phase cell start dividing and their no. Increase by
geometric progression with time.
During this phase :-
1. Bacteria have high rate of metabolism.
2. Bacteria develop best morphological with typical biochemical reaction.
3. Bacteria aee most sensitive to antibiotics at this stage.

7. Decline phase :-
 Durning this phase (few hrs to few days) population decrease due to death
of cell.
 Factors responsible for this phase are :-
 Toxic accumulation
 Nutritional exhaustion.
 Autolytic enzymes.
 Involuation (shrinkage of an organ in old age) is common phase of decline.

8. Survival:-
 When most organism have die, a few survive for several months to years.