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Microbial Nutrition and Growth
Chapter 6 Microbial Nutrition and Growth
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Result of microbial growth is discrete colony
Growth Requirements Microbial growth Increase in a population of microbes Result of microbial growth is discrete colony An aggregation of cells arising from single parent cell Reproduction results in growth 7/6/11 MDufilho 2
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Microbes obtain nutrients from variety of sources
Growth Requirements Organisms use a variety of nutrients for their energy needs and to build organic molecules and cellular structures Most common nutrients contain necessary elements such as carbon, oxygen, nitrogen, and hydrogen Microbes obtain nutrients from variety of sources 7/6/11 MDufilho 3
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Growth Requirements Associations
Organisms live in association with different species Antagonistic relationships Synergistic relationships Symbiotic relationships 7/6/11 MDufilho 4
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Growth Requirements Biofilms
Complex relationships among numerous microorganisms Develop an extracellular matrix Adheres cells to one another Allows attachment to a substrate Sequesters nutrients May protect individuals in the biofilm Form on surfaces often as a result of quorum sensing Many microorganisms more harmful as part of a biofilm 7/6/11 MDufilho 5
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Figure 6.17 Binary fission events-overview
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Growth of Microbial Populations
ANIMATION Binary Fission 7/6/11 MDufilho 7
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Figure 6.18 Comparison of arithmetic and logarithmic growth-overview
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Growth of Microbial Populations
Generation Time Time required for a bacterial cell to grow and divide Dependent on chemical and physical conditions 7/6/11 MDufilho 9
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Figure 6.19 Two growth curves of logarithmic growth-overview
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Figure 6.20 Typical microbial growth curve
Stationary phase Death (decline) phase Log (exponential) phase Number of live cells (log) Lag phase Time 7/6/11 MDufilho
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Figure 6.21 Schematic of chemostat
Fresh medium with a limiting amount of a nutrient Flow-rate regulator Sterile air of other gas Culture vessel Culture Overflow tube 7/6/11 MDufilho
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Growth of Microbial Populations
Measuring Microbial Reproduction Direct methods Serial dilution and viable plate counts Membrane filtration Most probable number Microscopic counts Electronic counters 7/6/11 MDufilho 13
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Figure 6.22 Estimating microbial population size-overview
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Figure 6.23 Use of membrane filtration to estimate microbial population-overview
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Inoculate 1.0 ml into each of 5 tubes
Figure The most probable number (MPN) method for estimating microbial numbers 1.0 ml 1.0 ml Undiluted 1:10 1:100 Inoculate 1.0 ml into each of 5 tubes Phenol red, pH color indicator, added Incubate Results 7/6/11 MDufilho 4 tubes positive 2 tubes positive 1 tube positive
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Figure 6.25 The use of a cell counter for estimating microbial numbers-overview
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Growth of Microbial Populations
Measuring Microbial Growth Indirect methods Metabolic activity Dry weight Turbidity 7/6/11 MDufilho 18
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Figure 6.26 Spectrophotometry-overview
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Growth of Microbial Populations
Measuring Microbial Reproduction Genetic methods Isolate DNA sequences of unculturable prokaryotes Used to estimate the number of these microbes 7/6/11 MDufilho 20
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Case Study–Can a trip to the dentist be life threatening?
Details of the case Why do we get our teeth cleaned? Why does Betty feel so bad? What has happened? Will the biofilm return? How did they figure out Betty had septicemia? 7/6/11 MDufilho 21
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