Chapter 6 (6-2,3)Microbial Growth and Its Control.ppt

Growth and Its Control
In Microbiology, growth is defined as an increase in the number of cells.
Control of Microbial Growth:
Physical ways,
Chemical ways.
Cell Growth
Growth rate is the change in cell number or mass per unit time.
The time interval for the formation of two cells from one is called generation time.
The number of cells doubles during each unit time period, is referred to as exponential growth.
Relationship between the number of cells present in a culture initially (N0) and the number present after a period of exponential growth (N):
N=N02n or n=(log(N)-log(N0))/log2
n=the number of generation
3 types of cell division: Fission, b. Budding, c. Multiple Fission
Binary Fission (二分裂)
Budding (芽殖)
Multiple Fission
Measuring cell density:
Turbidity vs Cell density
Measurement of cell growth
Total cell count (direct observation under microscope)
Viable count (plate count or colony count)
Spread plate method
Pour plate method
The plates required to have between 30 and 300 colonies.
Viable count: Spread plate methodand Pour plate method
Three basic steps:
Dilution,
Plating
Incubation
Viable Count: Dilution