Bacterial Growth Curve

Bacterial Growth Curve



• Bacterial growth follows a definite course when a bacterium is added to a suitable liquid

medium and incubated. .

• Growth curve is obtained when the bacterial counts made at intervals after inoculation is

plotted in relation to time.

Growth curve shows 4 phases.

1) Lag phase 2) Log phase 3) Stationary phase 4) Phase of decline

Lag phase

• No increase in the number but increase in the size of the cells – bacterial size is maximum.

• This phase is the time required for adaptation to new environment.

• Necessary enzymes and metabolic intermediates are produced in adequate quantities for

multiplication to proceed.



Log / Exponential / Logarithmic phase

• Division of the cells and increase in their number exponentially.

• Due to division, bacterial cell size is small and they stain uniformly.


Stationary phase

• Cell division stops due to depletion of nutrients and accumulation of toxic products.

• Progeny cells replace the dead cells.

• Equilibrium exists between dying cells and newly formed cells – viable count is

Stationary.

• Irregular staining, sporulation and production of exotoxins and antibiotics.

Phase of decline

• Bacterial cell death due to autolytic enzymes – decrease in population.

• Involution forms are common.