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Chapter 6

Chapter 6. Microbial Nutrition and Growth. 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. Growth Requirements.

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Chapter 6

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  1. Chapter 6 Microbial Nutrition and Growth

  2. 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 Growth Requirements MDufilho

  3. 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 Growth Requirements MDufilho

  4. Associations Organisms live in association with different species Antagonistic relationships Synergistic relationships Symbiotic relationships Growth Requirements MDufilho

  5. 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 Growth Requirements MDufilho

  6. Figure 6.17 Binary fission events-overview MDufilho

  7. Growth of Microbial Populations ANIMATION Binary Fission MDufilho

  8. Figure 6.18 Comparison of arithmetic and logarithmic growth-overview MDufilho

  9. Generation Time Time required for a bacterial cell to grow and divide Dependent on chemical and physical conditions Growth of Microbial Populations MDufilho

  10. Figure 6.19 Two growth curves of logarithmic growth-overview MDufilho

  11. Stationary phase Figure 6.20 Typical microbial growth curve Death(decline)phase Log(exponential)phase Number of live cells (log) Lag phase Time MDufilho

  12. Fresh medium witha limiting amountof a nutrient Flow-rateregulator Sterile airof othergas Figure 6.21 Schematic of chemostat Culturevessel Culture Overflowtube MDufilho

  13. Measuring Microbial Reproduction Direct methods Serial dilution and viable plate counts Membrane filtration Most probable number Microscopic counts Electronic counters Growth of Microbial Populations MDufilho

  14. Figure 6.22 Estimating microbial population size-overview MDufilho

  15. Figure 6.23 Use of membrane filtration to estimate microbial population-overview MDufilho

  16. 1.0 ml 1.0 ml Undiluted 1:10 1:100 Figure 6.24 The most probable number (MPN) method for estimating microbial numbers Inoculate 1.0 ml intoeach of 5 tubes Phenol red, pHcolor indicator,added Incubate Results MDufilho 4 tubes positive 2 tubes positive 1 tube positive

  17. Figure 6.25 The use of a cell counter for estimating microbial numbers-overview MDufilho

  18. Measuring Microbial Growth Indirect methods Metabolic activity Dry weight Turbidity Growth of Microbial Populations MDufilho

  19. Figure 6.26 Spectrophotometry-overview MDufilho

  20. Measuring Microbial Reproduction Genetic methods Isolate DNA sequences of unculturable prokaryotes Used to estimate the number of these microbes Growth of Microbial Populations MDufilho

  21. 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? Case Study–Can a trip to the dentist be life threatening? MDufilho

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