Growth b

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Growth b

  1. 1. Microbial Growth “ Because individual cells grow larger only to divide into new individuals, microbial growth is defined not in terms of cell size but as the increase in the number of cells, which occurs by cell division."
  2. 2. Binary Fission Note nascent septum forming
  3. 3. Planes of Division (1/3) Diplococcus Streptococcus
  4. 4. Planes of Division (2/3) Tetrad Sarcinae
  5. 5. Planes of Division (3/3) Staphylococcus
  6. 6. Exponential Growth Note Logarithmic Scale
  7. 7. Exponential Growth
  8. 8. Standard Bacterial Growth Curve (1/2)
  9. 9. Log Phase
  10. 10. Continuous Culture
  11. 11. Standard Bacterial Growth Curve (2/2)
  12. 12. Decline (Death) Phase
  13. 13. Solid Medium
  14. 14. Bacterial Colonies <ul><li>Standard Bacterial Count </li></ul><ul><li>Colony-Forming Units </li></ul><ul><li>Plaque-Forming Units </li></ul><ul><li>Spread Plate </li></ul><ul><li>Pour Plate </li></ul><ul><li>Soft-Agar Overlay </li></ul>
  15. 15. Soft Agar Overlay
  16. 16. Spread & Pour Plates
  17. 17. Dilutions and Limitations
  18. 18. Serial Dilution
  19. 19. Direct Microscopic Count
  20. 20. Most Probable Number Method
  21. 21. Most Probable Number Method Most Probable Number Calculations (based on 5 tubes/dilution) dilutions (10 0 = 1 ml culure) 10 0 10 -1 10 -2 10 -3 10 -4 MPN/ml 5 5 1 0 0 33 4 5 1 0 0 33 5 4 4 1 0 40 5 4 4 0 1 40 5 5 5 5 2 5400 0 0 1 0 0 0.20 4 4 1 1 0 4.7
  22. 22. Determination of Turbidity
  23. 23. pH Optima Neutrophiles
  24. 24. Acid-Based Microbial Succession
  25. 25. Acidophiles
  26. 26. Temperature Optima Also Psychrotrophs & Thermodurics
  27. 27. Thermophiles A large channel draining from a hot pool, containing carotenoid-rich microorganisms. The temperature of this channel in the foreground is about 60 o C. Layers of white-coloured limestone (forming a rock deposit known as travertine) can also be seen. Note the footprints of buffalo in the foreground. These animals often seek the warmth of thermal areas in the winter months. limestone terraces formed by precipitation from calcium-rich water flowing from a raised hot pool. Pink, green and brown-coloured microorganisms occupy the thermal gradients in the flowing water (60-100 o C)
  28. 28. Thermophiles
  29. 29. Deep-Sea Vents
  30. 30. Oxygen Requirements
  31. 31. Microaerophiles
  32. 32. Capnophiles
  33. 33. Growing Obligate Anaerobes <ul><li>Fluid Thioglycolate Medium </li></ul><ul><li>Peptones, Yeast Extracts, Glucose </li></ul><ul><li>Thioglycolate binds O 2 </li></ul><ul><li>Agar slows diffusion of O 2 </li></ul><ul><li>Resazurin is O 2 indicator (red) </li></ul>
  34. 34. Salt Tolerance
  35. 35. Nutrient Acquisition—Exoenzymes <ul><li>Secreted into environment </li></ul><ul><li>Catabolize food products </li></ul><ul><li>Protease, DNAase, Amylase, Lipase </li></ul><ul><li>Used in bacterial identification </li></ul>
  36. 36. Growing Fastidious Microbes
  37. 37. Selective Media
  38. 38. Differential Media
  39. 39. Diagnostic Media The concepts of Selective and Differential media can be confusing, particularly because very often media are both Selective and Differential
  40. 40. Microbial Growth!
  41. 41. Winogradsky Column Allows for the development of a redox gradient in a sample, from anaerobic through to H 2 S-rich Consists of water over sediment and substrate (sometimes with sand) Other components (e.g.., carbon sources, inorganic elements) often added. (these can be manipulated to select for different populations) AIR SAND Sediment Cellulose CaSO 4 + CaCO 3 Water
  42. 42. Winogradsky Column Example Winogradsky column (from Atlas and Bartha 1999) Microbial Zones reactions Algae, cyanobacteria CO 2 > CH 2 O, H 2 O > O 2 H 2 S - oxidizers H 2 S > S 0 , CO 2 > CH 2 O Facultative anaerobes CH 2 O > C0 2 + H 2 Purple non-sulfur CH 2 O > H 2 , CO 2 > CH 2 0 photoheterotrophs Purple Sulfur Bacteria H 2 S > S 0 , CO 2 > CH 2 O Green Sulfur bacteria H 2 S > S 0 , CO 2 > CH 2 O Sulfate reducers SO 4 2- > H 2 S, CH 2 O > CO 2 Fermentative heterotrophs CH 2 O > CO 2 + H 2 H 2 O AIR SAND Sediment Cellulose CaSO 4 + CaCO 3 Aerobic Microaerophilic Anaerobic H 2 S Redox Gradient

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