The bacterial growth curve represents the growth of a bacterial population over time in a closed system (batch culture).
It has four distinct phases:
Lag Phase of Bacterial Growth Curve:
Bacteria adapt to new environment.
Metabolic activity is high, but cell division is minimal.
Synthesis of enzymes, proteins, and other molecules needed for growth.
Log (Exponential) Phase:
Rapid cell division and exponential growth.
Population size doubles at a constant rate.
Nutrients are abundant, and metabolic activity is at its peak.
Generation time (time for the population to double) is calculated in this phase.
Stationary Phase:
Growth rate slows as nutrient depletion and waste accumulation occur.
Number of new cells equals the number of dying cells.
Metabolic activity continues, but at a reduced rate.
Secondary metabolites like antibiotics may be produced.
Death (Decline) Phase:
Nutrients are exhausted, and toxic waste products accumulate.
The number of dying cells exceeds the number of new cells formed.
The population declines at an exponential rate.
The graph above illustrates the bacterial growth curve, showing the distinct phases:
Lag Phase: Initial period where bacteria adapt to the environment.
Log (Exponential) Phase: Rapid increase in population as cells divide at a constant rate.
Stationary Phase: Growth rate slows as nutrients deplete and waste accumulates.
Death (Decline) Phase: Bacterial cells die at an exponential rate due to unfavorable conditions.
This representation highlights the dynamics of bacterial population growth in a closed system over time.