How many arrows do you see in the following shape?

1. How many arrows do you see in the following shape?

2. Microbial Growth Microbiology 2314

3. Bacterial Growth • Bacterial Growth is Bacterial Reproduction • The Numbers of Bacteria are Increasing • We see: 1. Observable Increases in Colonies Growing on Solid Media 2. Turbidity, Sediment, Scum or a Change in Color in Broth Cultures

5. Turbidity indicates bacterial numbers are increasing.

6. Binary Fission

8. Generation Time The Time Required for a Cell to Divide

9. Rapid Growth of Bacterial Population

11. Cockroaches Left Unchecked and Allowed to Multiply At Will

12. Generation Time N = (log10Nf – log10No ) / .301 N Number of generations Nf Final Concentration of Cells No Original concentration of cells .301 Conversion Factor to Convert Log2 to Log10

13. What is a Logarithm? • Logarithm is a functionthat gives the exponent in the equation bn = x. It is usually written as logbx = n. • For example: 34 = 81 Therefore log3 81 = 4

14. Example 1N = (log10Nf – log10No ) / .301 Measure Culture at 9:00 a.m. 10,000 cells / ml Measure Culture at 3:00 p.m. 100,000 cells / ml Calculate N N = (log10Nf – log10No ) / .301 N = (5-4)/0.301 N = 1/0.301 N = 3.33 Generations in 6 Hours We Know: 6 Hours = 360 Minutes Therefore: Generation Time = 360 Minutes / 3.33 Generations N = 108 Minutes to Generate

15. Example 2N = (log10Nf – log10No ) / .301 Measure Culture at 9:00 a.m. 10,000 cells / ml Measure Culture at Noon 1,000,000 cells / ml Calculate N

16. Example 2N = (log10Nf – log10No ) / .301 Measure Culture at 9:00 a.m. 10,000 cells / ml Measure Culture at Noon 1,000,000 cells / ml Calculate N N = (log10Nf – log10No ) / .301 N = (6-4)/0.301 N = 2/0.301 N = 6.64 Generations in 3 Hours We Know: 3 Hours = 180 Minutes Therefore: Generation Time = 180 Minutes / 6.64 Generations N = 27 Minutes to Generate

17. Example 3N = (log10Nf – log10No ) / .301 Measure Culture at 9:00 a.m. 2000 cells / ml Measure Culture at 1:00 p.m. 18,000 cells / ml Calculate N

18. Example 3N = (log10Nf – log10No ) / .301 Measure Culture at 9:00 a.m. 2000 cells / ml Measure Culture at 1:00 p.m. 18,000 cells / ml Calculate N N = (log10Nf – log10No ) / .301 N = (4.25-3.30)/0.301 N = .95/0.301 N = 3.16 Generations in 4 Hours We Know: 4 Hours = 240 Minutes Therefore: Generation Time = 240 Minutes / 3.16 Generations N = 75.9 Minutes to Generate N = 1.27 Hours to Generate

19. Bacterial Growth Can Be Modeled With Four Different Phases

20. Phases of Microbial Growth

21. Typical bacterial exponential Growth Curve. In a rich culture medium bacteria, grown under aerobic conditions, achieve a final concentration of 2-5 x 109 cells per ml in about 12-18 hours. Although plotted on a different time scale the human growth curve looks the same; the human population at similar points on the growth curve are shown in red.

22. Remember the Four Main Stages • Lag Phase Initial Phase / Metabolic Activities • Exponential Phase 2nd Phase / Optimum Growth / Doubling • Stationary Phase 3rd Phase / Exhaustion of Nutrients / Accumulation of Wastes • Death Phase Final Phase / Continued Accumulation 90% of Cells Die, then 90% of Remaining Cells Die, etc.

23. Quantification of Bacteria • Cell Numbers • Total Mass of the Population • Population Per Media cells / ml or cells / gram • Direct County Methods and Indirect Counting Methods

24. Direct Counting Methods • Normally Viable Counts • Remember that a Colony Starts Out as 1 Bacteria that Reproduces • Colonies May Not All Be The Same Size

25. Types of Direct Measurements • Plate Count a. Spread (Streak) Plate b. Pour Plate 2. Direct Observation on Slides a. Petroff-Hausser Chamber Slide 3. Filtration 4. Most Probable Number

26. Direct Count Spread or Streak Plate

31. Advantages to a Streak Plate?Disadvantages?

32. Direct Count Pour Plate

34. Advantages to a Pour Plate?Disadvantages?

35. Petroff-Hausser Chamber Slide

36. What are You Counting on a Petroff-Hausser Slide?

37. Direct Method Filtration

39. Most Probable Number • Statistical Procedure used to estimate the number of bacteria that will grow in liquid media. • Gives a 95% probability that the bacterial numbers will fall within a certain range.

40. Indirect Measurements Turbidity a. No turbidity = < 107 cells/ml b. Slight = 107 – 108 cells/ml c. High = 108 – 109 cells/ml d. Very High = > 109 cells/ml Metabolic Activity Dry Weight

41. There Are More Accurate Methods to Determine Turbidity Levels

42. Chemical and Physical Requirements for Bacterial Growth

43. Physical Requirements

46. Why is Mexican Food Spicy?

47. Oklahoma is #1

48. Cardinal Temperatures • Minimum Temperature • Optimum Temperature • Maximum Temperature

49. Classification of Bacteria by Temperature Requirements

50. Buffers Are Added to Media to Maintain Proper pH • Phosphates • Peptones • Amino Acids