BACTERIA'S GROWTH AND NUTRITION

                  INTRODUCTION 

1. The minimum nutrition requirement for growth and multiplication of bacteria includes sources of carbon , nitrogen, hydrogen, oxygen and some inorganic salts.

2. Bacteria divide by binary fission.

3. Generation time:  it is the time required for a bacterium to give rise to two daughter cells under optimum conditions.

4. Total count:  this indicates the total number of bacteria in the specimen, irrespective of whether they are living or dead.

5. Viable count: It measures the number of living ( viable) bacteria.

          

       BACTERIAL GROWTH CURVE

 When a bacterium is inoculated into a suitable culture medium and incubated, it's growth follows a definite courses. When bacterial count of such culture is determined at different intervals and plotted in relation to time , a growth curve is obtained .

The growth curve has four phases.

1.LAG PHASE: the period between inoculation and beginning of multiplication is known as Lag phase .

2. Log or Exponential phase :  The cell division starts and their number increased exponentially or by geometric progression with time. 

3. Stationary phase: The bacterial growth is almost completely due to exhaustion of nutrients and accumulation of toxic products.

4. Phase of Decline: The bacterial population decrease due to the death of cell. 

                  BACTERIAL NUTRITION 

:-  Obligate aerobes : the bacteria which grow only in the presence of oxygen. 

:- Facultative anaerobes :- The bacteria that are ordinary aerobes  but can also grow without oxygen . Most of the pathogenic bacteria are facultative in anaeropes.

:- Microaerophilic:- These bacteria can grow in the presence of trace of oxygen. 

:-  Anaerobes :-  The obligate or strict anaerobes can grow only in the absence of oxygen. 

:- Capnophilic bacteria:- These bacteria require much higher level of carbon dioxide ( 4-10 % ) for their growth epicially for primary isolation. 

:- Mesophiles :- The bacteria which grow optimally at temperature range of 25° C to 40° C majority of the pathogenic bacteria belong to this group.

:- Psychrophiles :-  These Victoria grow optimally at temperature below 20° C. 

:-  Thermophiles :- The optimum temperature for growth of this bacteria is between 55°  to 80° C.