文档介绍：Chapter4 Microbial growth
Isolation of pure cultures
the growth curve
Measurement of microbial growth
The continuous culture of anisms
Isolation of pure cultures
Pure culture: a population of cells arising from a single cell, to characterize an individual species. They are required for the careful study of an individual microbial species.
Single colony
How to get
1. Dilute-pour/spread plate technique:
dilutepour/spread isolated colonies
2. Streak plates: inoculating loop
Petri Disk Cultivation of a Pure Strain
The Streak Plate Technique: to obtain a pure clone
Laboratory Culture of anisms
% Agar
Colony morphology and growth
individual species often form colonies of characteristic size and appearance.
The growth of colonies on agar
At the colony edge: cells grow at maximum rates;
In the center of colony: cells are lying; growth is much slower
Cause: Oxygen, nutrients and toxic products
The colony center is much thicker than the edge.
Cell-munication and quorum sensing
Microbial growth
Batch culture:  When anisms are grown in a closed system, population growth remains exponential for only a few generations and then enters a stationary phase due to factors like nutrient limitation and waste accumulation.
Continuous Culture: If a population is cultured in an open system with continual nutrient addition and waste removal, the exponential phase can be maintained for long periods.
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The growth curve
The logarithm of the number of viable cells versus the incubation time.
The Growth Cycle of Populations
(a) Lag phase: cells begin to synthesize inducible enzymes and use stored food reserves.
(b) Logarithmic growth phase: the rate of multiplication is constant.
(c) Stationary phase: death rate is equal to rate of increase.
(d) Death phase: cells begin to die at a more rapid rate than that of reproduction.