《微生物学》课程教学课件（PPT讲稿）Chapter 4 Microbial growth

Chapter4 Microbial growth Isolation of pure cultures the growth curve Measurement of microbial growth The continuous culture of microorganisms

Chapter4 Microbial growth Isolation of pure cultures the growth curve Measurement of microbial growth The continuous culture of microorganisms

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 Dilute-pour/spread plate technique dilute→>pour/ spread→> isolated colonies 2. Streak plates: inoculating loop

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: dilute→pour/spread →isolated colonies 2. Streak plates: inoculating loop

Petri Disk Cultivation of a Pure strain 自

Petri Disk Cultivation of a Pure Strain

The streak Plate Technique to obtain a pure clone Bunsen burner Higher concentration of cells Lower concentration of cells Second set of streaks Fourth set of streaks

The Streak Plate Technique: to obtain a pure clone

Laboratory culture of microorganisms 5%Agar "F。。s

Laboratory Culture of Microorganisms 1.5% Agar

Colony morphology and growth individual species often form colonies of characteristic SIze and appearance Form 养米 Punctiform Circular Filamentous Irregular Rhizoid Spindle Elevation Raised Convex Pulvinate Umbonate Margin Entire Undulate Lobate Erose Filamentous Curled

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-cell communication and quorum sensing

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-cell communication and quorum sensing

Microbial growth Batch culture: When microorganisms are grown in a closed system, population growth remains exponential for only a few generations and then enters a stationary hase 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

Microbial growth • Batch culture: When microorganisms 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

The growth curve The logarithm of the number of viable cells versus the incubation time stationa Log number of living cells or turbidity death g Time(usually in hours) The growth Curve

. 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

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