BACTERIAL GROWTH CURVE

1. Dr. R. Haritha Lecturer in Biotechnology Visakha Government Degree College for Women Visakhapatnam BACTERIAL GROWTH CURVE

2. an increase in bacterial numbers does not refer to an increase in size of the individual cells What is Bacterial Growth?

3. Binary Fission - Most common method of reproduction - Asexual reproduction - Splitting of parent cell into two daughter cells Budding - Asexual reproduction - Outgrowths (buds) of mature organisms - Form of mitotic cell division - Bud separates as it reaches the size of the parent cell Bacterial Division

4. The population of bacterial cells divide at a constant rate so that the total number of cells doubles with each division Logarithmic or Exponential Growth

5. Microbial Growth Calculating Population Size A) Population growth is exponential 2  4  8  16  32  64  128… B) Population size can be calculated Nt = (No)2n a) Nt = final number of cells b) No = original number of cells c) n = number of divisions Example N0 = 10 cells in original population n = 12 • 4 hours assuming 20 minute generation time Nt = 10 x 212 Nt = 10 x 4,096 Nt = 40,960

7. Mean Generation Time / Doubling Time • The amount of time required for the concentration of cells to double during the log stage. • It is expressed in units of minutes. Growth rate (min-1) = • Depends on environmental conditions such as temperature or pH level. • Escherichia coli 20 mins • Mycobacterium tuberculosis 18 hrs • Mycobacterium leprae 14 days Generation time

8. Lag Log (logarithmic) Stationary Death Stages of Bacterial Growth

9. Growth curve or cycle

10. Period of little or no cell division Cells are not dormant Period of intense metabolic activity : DNA, RNA and enzyme synthesis Depend on type of bacterial species, culture medium, and environmental factors 1-4 hour long Lag Phase

11. Exponential or logarithmic phase Growth is Exponential i.e., shows logarithmic increase Cellular respiration is most active during this period Metabolic activity is active and is most preferable for industrial purposes Sensitive to adverse conditions 8 hrs long Log Phase

12. Period of equilibrium Metabolic activity of surviving cells slows down which stabilizes the population Exhaustion of nutrients, accumulation of waste products and harmful changes in Ph Few hours to days Stationary Phase

13. Also known as Logarithmic Decline Phase. Exhaution of nutrients, accumulation of toxic products and autolytic enzymes. Some population dies out completely. Others retain surviving cells indefinitely while others only retain for a few days. Death Phase

14. Amount of nutrients Temperature pH Other Environmental factors Factors affecting Bacterial Growth

15. Bacteria grow non synchronously in culture medium Synchronous growth- When all bacterial cells in culture medium divide simultaneously. Chemostat – Continuous culture used in industrial fermentation Synchronous growth is for studies on - DNA synthesis - Susceptibility of cell to lethal agent Synchronous growth

17. Generation time of E.coli is........ A • 20 hours C • 20 Mins • 20 Mins D • 200 hours B • 20 days

18. Starvation o Bacteria occurs during which of the following phases of Growth? C A Lag Phase • Log Phase Death Phase • Stationary Phase B D Death Phase

19. During Exponential growth, the Growth rate is....... A • No. of Generations per unit time C • Both A & B • Both A & B D • None of these B • Reciprocal to Generation Time

20. In which of the following Phases, the Growth rate is equal to the Death rate? Stationary Phase C A Stationary Phase • Log Phase • Lag Phase B D Death Phase

21. If we begin with 4 cells & ended up with 128 cells. How many Generations did the cell go through? A • 64 C • 6 • 6 B • 32 D • 7