Bacterial Growth Curve :

Bacterial Growth Curve : ___/``````\___

The Bacterial Growth Curve represents the number of live cells in a bacterial population over a period of time.There are four distinct phases of the Growth curve : 

¹.Lag , 

².Exponential (log), 

³.Stationary, &

⁴.Death. 

The growth of bacteria (or other microorganisms, as protozoa, microalgae or yeasts) in batch culture can be modeled with Four different Phases : lag phase (A), log phase or exponential phase (B), stationary phase (C), and death phase (D)

                             ___/``````\___

The initial phase is the lag phase where bacteria are metabolically active but not dividing.Bacterial growth is proliferation of bacterium into two daughter cells, in a process called binary fission.Providing no event occurs, the resulting daughter cells are genetically identical to the original cell. Hence, bacterial growth occurs.

¹.Lag Phase : ⏸ ___

Acclimatization -(Process of adjusting to a new environment habituation)

When cells are in the stationary phase growth of bacterial cultures are transferred to fresh media for the lag phase occurrence.

The lag phase is due to thie situation of time required for the physiological adaptation of stationary phase cells in preparation for the growth.

The lag phase can ve due to the time required for the recovery of cells from toxic products of metabolism that may accumulate in the external medium such as Acids, Bases, Alcohols or Solvents.lag phase can be avoided if the inoculation is taken from the exponential phase of the growth and transferred to fresh medium of thr same compositions.

².Log Phase (Exponential Phase) : ↗️ /

After the lag phase the organisms adjust themselves to their new environment cell begins to grow and devide at the exponential rate characteristics.

If their is single source of Carbon the population of cell will be continue to grow at the same rate until they have almost exhausted the substrates.In more complex media containing mixtures of substrates the organisms can control their utilization of substrates so that one can consumed it first ten others until all are exhausted under these conditions the slope of the growth curve is not constant.

³.Stationary Phase : ➡️ ----

The reason behind why the cells stop growing and enter into stationary phase because of the exhaustion of Nutrients, Limitation of Oxygen or the accumulation of the toxic products such as Alcohol, Acids and Bases.The accumulation of toxic product is a problem for fermenting cells because most of the nutrients are not converted into cell required material but excreted as waste product.

Unnecessory components are slowly degraded to provide energy required for maintain the cells where in stationary phase some micro-organism can survive for the extensive periods.

⁴.Death Phase : ↘️ \

Death Can be result from several factors including the depletion of the cellular energy and activity of catalytic enzymes.Some bacteria are die within hours(hrs) of entering the stationary phase.However many bacteria remain viable for longer periods.

Example -

Some Bacteria sporulate or form cysts in exponential phase.

The spores and cysts are resting cells that remain viable for and germinate in the fresh media.

                   Bacterial Growth Curve