Microbiology: Control of Microorganisms
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Questions and Answers

Which scientist developed the criteria now known as Koch's postulates?

  • John Tyndall
  • Louis Pasteur
  • Ferdinand Cohn
  • Robert Koch (correct)
  • What did John Tyndall demonstrate about dust?

  • It can carry microorganisms (correct)
  • It is responsible for spontaneous generation
  • It fixes atmospheric nitrogen
  • It is necessary for the process of photosynthesis
  • Which role is not performed by microorganisms in nature?

  • Fixing atmospheric carbon
  • Regulating weather patterns (correct)
  • Decomposing organisms to recycle nutrients
  • Fixing atmospheric nitrogen
  • Which microorganism-related product is incorrectly paired?

    <p>Riboflavin - Antibiotics</p> Signup and view all the answers

    Which activities were demonstrated by Ferdinand Cohn?

    <p>Establishing the relationship between Bacillus anthracis and anthrax</p> Signup and view all the answers

    What did the germ theory of disease disprove?

    <p>The theory of spontaneous generation</p> Signup and view all the answers

    Which suffix is used to identify methods that cause the killing of microorganisms?

    <p>-cide</p> Signup and view all the answers

    Which of the following treatments stops the growth of bacteria without killing them?

    <p>Bacteriostatic</p> Signup and view all the answers

    What factors determine whether a treatment is -cidal or -static?

    <p>Concentration of chemical used, nature of treatment, types of microorganisms</p> Signup and view all the answers

    In microbial control, what does the Decimal reduction time (D-value) represent?

    <p>Time taken for a treatment to reduce the microbial population by 90%</p> Signup and view all the answers

    How is the effectiveness of an antimicrobial treatment commonly plotted in a microbial death curve?

    <p>As semi-log plots depicting logarithmic reduction in the microbial population</p> Signup and view all the answers

    Which statement best describes the microbial death curve?

    <p>The rate of killing remains constant as a fixed percentage of the population.</p> Signup and view all the answers

    Which suffix indicates a method that kills targeted microorganisms?

    <p>-cide</p> Signup and view all the answers

    What factors determine the level of treatment required for reducing microbes on fomites?

    <p>Application for which the item will be used and resistance of potential pathogen</p> Signup and view all the answers

    Which example illustrates a method that stops microbial growth rather than killing the microorganism?

    <p>Bacteriostatic</p> Signup and view all the answers

    What does a D-value represent in microbial death curves?

    <p>Time required for a 90% reduction in the microbial population</p> Signup and view all the answers

    Which of the following factors does NOT determine the effectiveness of a microbicide?

    <p>Color of the microbicide</p> Signup and view all the answers

    How is the microbial death rate typically expressed on a death curve?

    <p>As a percentage decrease in the microbial population</p> Signup and view all the answers

    Why do canned foods require a higher treatment level for microbial control compared to clothing?

    <p>Because they can harbor resistant spores</p> Signup and view all the answers

    Which microbial control method is described by the suffix -static?

    <p>Methods that inhibit the growth of microorganisms</p> Signup and view all the answers

    Study Notes

    Measuring Control of Microorganisms

    • Methods that kill microorganisms (suffix -cide or -cidal) include:

      • Bactericides, which kill bacteria
      • The prefix identifies the type of microbe being killed
    • Methods that stop microbial growth (suffix -stat or -static) include:

      • Bacteriostatic, which inhibits bacterial growth
      • Fungistatic, which inhibits fungal growth
    • Factors affecting the -cidal or -static nature of a method include:

      • Type of microorganism being targeted
      • Concentration of chemical used
      • Nature of the treatment applied

    Microbial Control

    • Microbial death curve:
      • Describes the progress and effectiveness of an antimicrobial treatment
      • Often plotted as a semi-log plot, similar to microbial growth curves
      • Rate of killing remains constant as a fixed percentage of the microbial population
      • D-value (decimal reduction time) measures the effectiveness of an antimicrobial treatment
      • D-value is the time taken for a specific treatment to result in the death of 90% of the microbial population

    Microorganisms

    • Microorganisms are ubiquitous and play essential roles in nature
    • They:
      • Photosynthesize and fix atmospheric carbon
      • Fix nitrogen and enrich soil
      • Recycle nutrients back to soil when organisms die
      • Benefit mankind in food production, beverage manufacturing, and vitamin production

    Microorganisms and Disease

    • John Tyndall showed that dust carries microorganisms
    • Ferdinand Cohn established a relationship between Bacillus anthracis and anthrax
    • Robert Koch developed criteria to prove that disease is caused by a microorganism
    • Koch's postulates are still used today to establish the relationship between disease and microorganisms

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    Description

    Learn about the methods to control microorganisms, including killing and stopping the growth of infecting agents. Understand the differences between cidal and static methods.

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