The document discusses various ways to monitor and measure bacterial growth, including direct and indirect methods. Direct methods involve counting cells directly, such as through plate counts, filtration, or microscopic counts. Indirect methods measure growth factors associated with cells, like turbidity, metabolic activity by products, or dry cell weight. The document provides details on calculations for determining generation time and number of generations from growth curve data.

1. The Growth of Bacterial Cultures
Ways of monitoring and measuring
growth, directly and indirectly
Prof. Dr. Mohammad Minnatul karim
Department of Biotechnology and Genetic Engineering
Islamic University, Kushtia

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

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

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

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. Figure 6.14
Phases of Growth

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)
Figure 6.15
Bacterial Lawn

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

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. 600nm to measure Pichia growth
Optical Density Measurement

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