BIOS 2150 Microbiology_Class_Notes Physiology

BIOS 2150 Microbiology Tuesday 9/18/18


Exams will be back to you on Thursday right before break.

Unit 2: Physiology

1. Compare and demonstrate the use of the techniques used to measure microbial
growth and population size.

Bacterial Growth

Generation Time (Chapter 9 page 362)
 Time required for a cell to divide
o 20 minutes to 24 hours
 We looked at two ways that this could happen
o Binary Fission
o Mitosis

Bacterial Growth Curve
1. Lag phase: no increase in number of living bacterial cells
2. Log phase: exponential increase in number of living bacterial cells
3. Stationary Phase: plateau in number of living bacterial cells; rate of cell
division and death roughly equal
4. Death or decline phase: exponential decrease in number of living bacterial
cells

Bell-Shaped Growth Curve
1. Lag Phase
a. Metabolically really busy
b. Manufacturing the things that they need to divide
c. Even though the numbers are not there, the activity is massive
d. “Behind the scenes work”
2. Exponential Growth Phase / Log Phase
a. “Logarithmic growth”
b. Mr. Templeton prefers the term “Exponential Growth”
c. Has enough nutrients, has the right temperature, plenty of room to
grow, conditions are ideal for growth
d. Consider west Omaha growing faster than other areas of town
3. Stationary Phase
4. Death or decline phase:
a. Run out of nutrients

Now that we know that they are growing, the next question is how many do we
have?




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