1. Microbial Growth and Culture
DARLINA DAUD

2. Growth and Cell Division
Microbial Growth Defined:
Mother or parent cell doubles in size
Divides into two daughter cells
Microbial growth is defined as the increase in the number of cells, which occurs by cell division

3. Cell Division
Binary fission (equal cell division): A cell duplicates its components and divides into two cells
Septum: A partition that grows between two daughter cells and they separate at this location
Budding (unequal cell division): A small, new cell develops from surface of exisiting cell and subsequently separates from parent cell

4. Binary Fission

5. Thin section of the bacterium Staphylococcus, undergoing binary fission

6. Environmental Factors Influencing Growth
Temperature O2 pH
Osmotic Pressure
Others: radiation,
atmospheric
pressure

7. Temperature Psychrophiles: cold-loving
Mesophiles: moderate temperature-loving
Thermophiles: heat-loving
Each has a minimum, optimum, and
maximum growth temperature

9. Oxygen Obligate aerobes Facultative anaerobes Obligate anaerobes
Aerotolerant
Microaerophiles

10. pH
Acidophiles
Neutrophiles
Alkalophiles

11. Osmotic Pressure

12. Phases of Growth
Consider a population of organisms introduced into a fresh, nutrient medium
Such organisms display four major phases of growth
The lag phase
The logarithmic phase
The stationary phase
The death phase

14. The Lag Phase Organisms do not increase significantly in number
They are metabolically active
Grow in size, synthesize enzymes, and incorporate molecules from medium
Produce large quantities of energy in the form of ATP

15. The Log Phase Organisms have adapted to a growth medium
Growth occurs at an exponential (log) rate
The organisms divide at their most rapid rate
a regular, genetically determined interval (generation time)

16. Stationary Phase:
Cell division decreases to a point that new cells are produced at same rate as old cell die.
The number of live cells stays constant.
Decline (Death) Phase:
Condition in the medium become less and less supportive of cell division
Cell lose their ability to divide and thus die
Number of live cells decreases at a logarithmic rate

17. Growth in Batch Culture
Growth is generally used to refer to the acquisition(perolehan) of biomass leading to cell division, or reproduction
A “batch culture” is a closed system in broth medium in which no additional nutrient is added after inoculation of the broth

18. Growth in Continuous Culture
A “continuous culture” is an open system in which fresh media is continuously added to the culture at a constant rate, and old broth is removed at the same rate.
This method is accomplished in a device called a chemostat.
Typically, the concentration of cells will reach an equilibrium level that remains constant as long as the nutrient feed is maintained.

19. Standard Growth Curve