Bacterial Reproduction and Growth

Bacterial Reproduction

• Binary fission is the method bacteria use to increase their numbers.
• One bacterial cell divides into two identical daughter cells.
• The daughter cells are similar to the parent cell.

Bacterial Generation Time

• Bacterial generation time is the time it takes for a bacterial population to double in number.
• For many common bacteria, the generation time is between 20-60 minutes under optimal conditions.

Steps of Binary Fission (Visual Aid)

• DNA Replication: The bacterial DNA replicates.
• Cell Elongation: The cell elongates, preparing to divide.
• Septum Formation: A septum forms to divide the cell into two compartments.
• Completion of Septum: The septum formation is complete and distinct walls form.
• Cell Separation: The two daughter cells separate.

Bacterial Growth Curve

• Bacteria are grown in a liquid nutrient medium.
• Bacteria are counted at regular intervals.
• The results are plotted to create a growth curve.
• The bacterial growth curve has four distinct phases: lag phase, exponential (log) phase, stationary phase, and death (decline) phase.

Phases of Bacterial Growth Curve

Lag Phase

• Initial phase where bacteria adapt to the environment.
• No cell division happens during this phase.
• Bacteria synthesize enzymes and molecules needed for replication.
• Few live cells, many dead cells initially.

Exponential (Log) Phase

• Rapid cell division occurs during this phase.
• The number of bacterial cells steadily increases over time.
• This is the best time for antibiotic action.
• Differentiate between 'rapid grower' and 'slowly grower'

Stationary Phase

• Nutrients in the medium become depleted.
• Toxic products accumulate.
• Rate of bacterial growth decreases.
• Number of dying cells equals the number of new cells formed.
• Number of living bacteria remains relatively constant.

Death Phase

• Nutrient exhaustion and toxic buildup continues.
• Death rate exceeds the multiplication rate.
• Number of living bacteria decreases.