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The Growth of Bacterial Cultures

The Growth of Bacterial Cultures. Ways of monitoring and measuring growth, directly and indirectly. Reproduction in Prokaryotes. Bacteria normally reproduce through Binary fission

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The Growth of Bacterial Cultures

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  1. The Growth of Bacterial Cultures • Ways of monitoring and measuring growth, directly and indirectly

  2. Reproduction in Prokaryotes • Bacteria normally reproduce through Binary fission • There are a few bacterial species that reproduce through Budding,Conidiospores (actinomycetes), or by Fragmentation

  3. Binary Fission Figure 6.11

  4. Generation Time -Time required for cell to divide (and its population to double) Figure 6.12b

  5. Why we use logarithmic graphing for bacterial growth Figure 6.13

  6. Calculations • If 5 cells were allowed to divide 9 times Then, 5 x 29 = 2560 cells • To calculate the number of generations, you need to convert into logarithms. The log of 2 (0.301) is used because one cell divides into two Refer to Appendix D of your textbook

  7. If 100 cells growing for 5 hours produced 1,720,320 cells: = log 1,720,320 – log 100 = 6.2356 - 2 =14 generations 0.301 0.301 = 60 minutes x 5 hours = 21minutes/generation 14 generations *These calculations are useful to compare growth conditions

  8. Phases of Growth Figure 6.14

  9. Direct Measurements of Microbial Growth • Plate Counts • Filtration • Direct Microscopic Count

  10. Direct Measurements of Microbial Growth • Plate Counts: Perform serial dilutions of a sample Figure 6.15, top portion

  11. Plate Count • Inoculate Petri plates from serial dilutions Figure 6.16

  12. Plate Count • After incubation, count colonies on plates that have 25-250 colonies (CFUs) Bacterial Lawn Figure 6.15

  13. Cell Viability Measurement: Spread Plate Optimal number to count is 30-300 colonies

  14. Direct Measurements of Microbial Growth • Filtration Figure 6.17a, b

  15. Direct Measurements of Microbial Growth • Multiple tube MPN test • Count positive tubes and compare to statistical MPN table. Figure 6.18b

  16. Direct Measurements of Microbial Growth Figure 6.19

  17. Direct Measurements of Microbial Growth • Direct Microscopic Count

  18. Indirect Measurements of Microbial Growth • Turbidity • Metabolic Activity • Dry weight

  19. Estimating Bacterial Numbers by Indirect Methods • Turbidity Figure 620

  20. Optical Density Measurement 600nm to measure Pichia growth

  21. Estimating Bacterial Numbers by Indirect Methods • Metabolic Activity -measure product as a function of time Example: Bacterial culture produces acid as a metabolic product, therefore you can monitor growth by monitoring change in pH over time. • Dry weight-filter all cells, dry in desiccator, and weigh on scale

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