chapter 6: measuring microbial growth microbial growth requirements

1. chapter 6: measuring microbial growth microbial growth requirements

2. binary fission & biotic potential

3. microbial population growth

4. direct methods: dilution & plating The spread plate method Inoculate plate containing solid medium. 100μl Bacterial dilution Spread inoculum over surface evenly. Colonies grow only on surface of medium.

5. direct methods: microscopic counts

6. indirect methods: most probable number

7. indirect methods: spectrophotometry

8. growth requirements: temperature

9. growth requirements: temperature

10. food spoilage

11. growth requirements: osmotic pressure osmoprotectants/compatible solutes

12. growth requirements: pH • membrane proteins gather H+ or OH- • proton pumpsNa+/H+ symport & antiport

13. living with oxygen: anti-oxygen enzymes

14. oxygen requirements

15. chemical growth requirements biological macromolecule synthesis

16. media: meeting physical & chemical needs

17. media

18. special media types differential & selective media

19. Chapter Six Learning Objectives • How do most bacterial cells reproduce? Why do bacterial cells have tremendous biotic potential? • Discuss what is happening to a bacterial culture during the fourth phases of population growth. Are they growing, dividing, what is driving the change in population number? • Categorize, discuss the pros and cons and understand the mechanism of action for each of the following methods of counting the number of bacterial cells in culture: serial dilution and spread plating, microscopic counts, MPN, and spectrophotometry. • How do temperature, osmotic pressure, pH and oxygen changes affect the growth of a bacterial culture? How are organisms classified according to their needs in regard to these physical aspects of the environment? What adaptations might various bacterial species have in order to combat less than desirable environments? • Six chemical growth requirements were discussed in lecture. What are these used for in the bacterial cell? How does the availability of these affect the growth of a bacterial culture? • How are differential and selective media useful in isolating, identifying and enriching for particular bacterial species? • How do complex and chemically defined media differ? When is each useful for the routine culture of bacterial cultures?

20. chapter seven: control of microbial growth

21. the control of microbial growth

22. treatment effectivity • number of microbes/length of exposure • microbial characteristics • environment: moisture & temperature • organic matter • vegetations/biofilms 1. cells populate substrate 2. extracellular polymeric substances (EPS) produced & attaches 3 & 4. biofilm architecture develops and matures 5. cells are released from the biofilm

23. the benefits of a biofilm protection from Abx, toxins and immune cells tobramycin ciprofloxacin    planktonic cells biofilm cells biofilm colony open symbols are untreated (control)

24. terminology • decimal reduction time (DRT)- opposite of decimate • thermal death point (TDP) • lowest temperature when all cells killed in 10 min. • thermal death time (TDT) • time to kill all cells at given T

25. heat • dry heat- oxidation • flaming • incineration • hot-air sterilization • moist heat- denaturization • autoclave • pasteurization • not sterile • 63°C for 30 min • flash (UHST): 72°C for 15 sec • ultra heat treatment (UHT):>135°C for <1 sec • moist vs. dry • hot air: 170˚C, 2 hr • autoclave: 121˚C, 15 min

26. filtration • physical removal of organisms • protects heat-labile components

27. ionizing & nonionizing radiation

28. ionizing radiation

29. dip metal ring in bacteria dry at 37°C place ring in disinfectant 10 minutes @ 20°C culture in broth check survivability chemical control: use-dilution test useful for testing bactericidal properties

30. filter paper is soaked with disinfectant paper placed on“seeded” agar plate incubated examined for zone of inhibition chemical control: disk-diffusion method

31. * chemical microbial control

32. for study

33. Chapter Seven Learning Objectives • Define sterilization, commercial sterilization, disinfection, antisepsis, degerming and sanitization. Understand what is meant by “-stat,” “-lytic” and “-cide”. • How do the following affect the effectivity of a given microbial control agent: microbial load, exposure length, microbial characteristics, moisture, temperature, organic matter and vegetations/biofilms? • How is a biofilm produced? How are the microbes within it so protected from the environment? • Why is moist heat better than dry heat at killing microbes? • Define thermal death point, thermal death time, and decimal reduction time. • When is filtration a useful method of controlling microbial growth? • How do ionizing and non-ionizing radiation work to control microbial growth? • What experimental method discussed in class is useful to determine the bactericidal properties of a given chemical? Which would you use if you were only concerned with the bacteriostatic properties? • How would you rate the various kinds of microorganisms in terms of their resistance to the chemical control of microbial growth?

34. chapter eight: microbial genetics

35. the hereditary materialGriffith 1927 & Avery, et al. 1944 the “transforming principle” coined by Griffith, identified by Avery

36. the hereditary materialHershey Chase, 1952

37. the bacterial chromosome

38. plasmids • F factor (conjugative plasmid) • genes for sex pili and plasmid transfer • dissimilation plasmids • enzymes to catabolize unusual compounds • R factors • antibiotic resistance