Ch #3 - Phases of Bacterial Growth

Bacterial Life Cycle

• Time and number of bacteria produced in one growth period

• Occurs under ideal conditions

  • Moist environment

  • Nutrient rich

  • Ideal temperature

Step #1 - Lag Phase

• Bacteria learn environment and gear up for replication

  • Increases cell size, metabolism, and protein production

Step #2 - Log Phase

• Bacteria activate division and replication

  • Experience exponential growth

  • Most susceptible to antibiotics and disinfectants

Step #3 - Stationary Phase

• Nutrients are used up and there is decreased O2

  • Rate of Replication = Rate of Death

  • Enter survivor mode

    • Slow down growth, begin sporulation, and make secondary metabolites

    • Antibiotics = Helps bacteria survive longer

    • Virulence = Helps bacteria infect better

Step #4 - Death Phase

• Exponential death occurs

  • Increase in toxic waste

  • Endospores are released

  • Some bacteria experience lyse

  • Persistor Cells form

    • Persistor Cells = Cells that do not die and have antibiotic resistance