chapter 2 physiology of bacteria section 1 and section 2(study by yourself)
TRANSCRIPT
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Chapter 2 Physiology of
Bacteria
Section 1 and section 2(study by yourself)
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Ⅳ.the bacterial metabolic products of biosynthesis(p31)
A.pyrogen:It is polysaccharide in nature ,resistant to high heat even at 120℃/20min , usually use distill
B.Exotoxin:secrete toxic subtance
C.Endotoxin: G-,toxic component from the cell wall
D.Pigments:
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E.antibiotic:A few of bacteria produce some bactericidal or bacteristasis substances that are known as antibiotics
F.Bacteriocin
G.Vitamin
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Section3 Bacterial growth and multiplication
Bacteria replicate by binary fission and undergo exponential growth
Number of cells 1 2 4 8 16Exponential 20 21 22 23 24
Definitions: Binary fission: process in which one bacterium splits into two
cells.
Generation time: The time it takes a population of bacteria
to double in number.
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Requirements for bacterial growth
Nutritional requirements
Water
Carbon source: CO2, glucose, sucrose, etc.
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Nitrogen source: N2, nitrates, ammonia, etc
Inorganic salts: S, P, K, Mg, Ca, etc.
Growth factors: organic compounds that a cell must have for growth but cannot synthesize itself.
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pH
1. Many bacteria grow best at neutral pH.
2. Some specialized bacteria can survive and even grow in acid or alkaline conditions.
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TemperatureTemperature
Bacteria may grow at a variety of temperatures fromclose to freezing (pyschrophile) to near to the boilingpoint of water (thermophiles).
Mesophiles: grow best at human body temperature(includes all human pathogens and opportunists)
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Requirements for bacterial growth
Gas requirementsOxygen (O2)
Obligate aerobes: organisms that grow only in the presence of
oxygen.Microaerophiles: organisms that require a low concentration of
oxygen (about 4%) for growth, but higher concentrations are inhibitory.
meningitides
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Obligate anaerobes: organisms that grow only in the absence of
oxygen and, in fact, are often inhibited or killed by its presence.
Facultative anaerobes: organisms that grow with or without oxygen,
but generally better with oxygen.
Carbon dioxide (CO2): e.g., Neissria
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Measuring bacterial mass in liquid cultures.
Common methods include:
Turbidity
1. The cloudiness of a liquid culture of bacteria.
2. A measure of total bacteria [live and dead].
3. This is usually quantitated with a spectrophotometer.
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Determination of the number of viable bacteria in a culture.Usually assessed by counting the number of colonies that grow after streaking a known volume on a plate ("plate counting" of colony forming units).
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Bacterial growth-Standard growth curve Lag phase: The number does not increase; Metabolism is active;Lasts for a few minutes to several hours.
Exponential phase / log (logarithmic) phaseDivide at their most rapid rate;
Size, shapes, biochemical activation, and sensitivity to antimicrobial agents of
bacteria are typical.
Lasts for 8-18hrs
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Bacterial growth-Standard growth curve
Stationary phaseThe number of live cells is constant.Spores, exotoxins, and antibiotics are produced.
Decline phaseThe number of live cells decreases.
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Media for laboratory studies
Basal mediumEnriched mediunSynthetic mediumDifferential mediumSelective mediumAnaerobic medium
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Media for laboratory studies
Liquid medium
solid medium
semi-solid medium
triangular flask
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inoculating loopalcohol lamp
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Blood Agar PlateBlood Agar Plate
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Some question
What is the growth curve?why?
The enviromental factors effecting growth include?