Microbial Nutrition: Macronutrients and Micronutrients
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Questions and Answers

What percentage of cell dry weight is composed of a few major elements?

  • 50%
  • 95% (correct)
  • 75%
  • 99%

    • Which of the following macroelements is required for the activity of enzymes involved in protein synthesis?

  • Calcium (Ca2)
  • Potassium (K) (correct)
  • Iron (Fe2 and Fe3)
  • Magnesium (Mg2)

    • What is the primary function of magnesium in the cell?

  • Stabilizes ribosomes and cell membranes
  • Participates in electron transport chains
  • Serves as a cofactor for many enzymes (correct)
  • Contributes to heat resistance of bacterial endospores

    • What is the role of iron in the cell?

    <p>Serves as a cofactor for enzymes and electron-carrying proteins</p> Signup and view all the answers

    What are the four macroelements that exist in the cell as cations?

    <p>Potassium, calcium, magnesium, and iron</p> Signup and view all the answers

    What is the primary function of carbon in the cell?

    <p>Forms the skeletons or backbones of all organic molecules</p> Signup and view all the answers

    What is the primary mechanism of extinguishing a candle's flame in a candle jar?

    <p>Oxygen deprivation</p> Signup and view all the answers

    What type of microorganisms are typically grown in candle jars?

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

    What is the purpose of inoculating the second half of the Petri dish with Serratia marcescens?

    <p>To consume oxygen</p> Signup and view all the answers

    What is the main purpose of maintaining quality control (QC) stocks in a microbiology laboratory?

    <p>To test culture media, kits, and reagents</p> Signup and view all the answers

    What is the primary reason for maintaining the purity of a microorganism in a pure culture?

    <p>To prevent contamination</p> Signup and view all the answers

    What is the purpose of sealing the Petri dish with wax or paraffin?

    <p>To prevent contamination</p> Signup and view all the answers

    What is a characteristic of obligate anaerobes?

    <p>They can live only in the absence of oxygen</p> Signup and view all the answers

    What is the primary function of extracellular electron transfer in microorganisms?

    <p>To capture or deliver electrons to donors or acceptors</p> Signup and view all the answers

    Why are anaerobes killed by oxygen?

    <p>Because they lack enzymes such as catalase, peroxidase, and superoxide dismutase</p> Signup and view all the answers

    What is the primary reason why Fe(II) is more available to microorganisms than Fe(III)?

    <p>Fe(II) is more soluble than Fe(III) at neutral pH</p> Signup and view all the answers

    What is the purpose of Fe(II) oxidizing microorganisms coupling the oxidation of iron to intracellular reduction of oxygen, carbon dioxide, and nitrate?

    <p>To avoid cell encrustation</p> Signup and view all the answers

    What is the purpose of boiling the culture medium during the preparation of Prereduced media?

    <p>To drive off most of the dissolved oxygen</p> Signup and view all the answers

    What is the function of superoxide dismutase in anaerobic bacteria?

    <p>To convert superoxide to hydrogen peroxide</p> Signup and view all the answers

    What is the essential requirement for microorganisms to grow?

    <p>Incorporation of large quantities of nitrogen, phosphorus, and sulfur</p> Signup and view all the answers

    Why are specimens from the throat or vaginal swab not submitted for anaerobic culture?

    <p>Because they are contaminated with anaerobes</p> Signup and view all the answers

    What is the result of microorganisms changing the redox state of metals?

    <p>The metals become more bioavailable</p> Signup and view all the answers

    What is the purpose of adding a reducing agent, such as cysteine, to the culture medium during the preparation of Prereduced media?

    <p>To decrease the oxygen content</p> Signup and view all the answers

    Where do microorganisms carry out the process of extracellular electron transfer?

    <p>Extracellularly, outside the cell boundaries</p> Signup and view all the answers

    At what temperature should isolates be stored for long-term preservation?

    <p>-70°C or below</p> Signup and view all the answers

    What is the recommended method for long-term preservation of bacterial culture?

    <p>Freezing at -70°C or below</p> Signup and view all the answers

    How often should non-fastidious organisms be thawed, reisolated, and refrozen when frozen at -70°C?

    <p>Every five years</p> Signup and view all the answers

    What is the purpose of adding a cryoprotectant to a solution when storing viruses at -70°C?

    <p>To protect the viruses from freezing damage</p> Signup and view all the answers

    What is the temperature of an ultralow freezer?

    <p>-70°C</p> Signup and view all the answers

    What is the term for freezing in liquid nitrogen at -196°C or in the gas phase above the liquid nitrogen at -150°C?

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

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