Microbiology Lab Techniques and Bacteria
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Questions and Answers

What is required for bacteria to perform fermentation?

  • Temperature control
  • Nutrient medium
  • Oxygen source
  • Carbon source (correct)

    • Which term describes an organism that thrives in high temperatures?

  • Thermophile (correct)
  • Mesophile
  • Halophile
  • Psychrophile

    • What effect does immersion oil have when using a microscope?

  • Increases magnification
  • Eliminates light refraction (correct)
  • Increases light penetration
  • Decreases resolution

    • Why do smaller wavelengths provide better resolution in microscopy?

    <p>They diffract less around the object</p> Signup and view all the answers

    What does the enzyme catalase do?

    <p>Detoxifies free radical oxygen molecules</p> Signup and view all the answers

    What is the first step in the Gram stain procedure?

    <p>Prepare a heat-fixed slide</p> Signup and view all the answers

    Which type of bacteria is described as having a thick peptidoglycan layer?

    <p>Gram-positive bacteria</p> Signup and view all the answers

    Which shape is described as spiral-shaped and flexible?

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

    What indicates that Streptococcus pneumoniae is susceptible to Bacitracin?

    <p>Presence of colored circles around bacteria</p> Signup and view all the answers

    Which option describes the colony margin of Gram-negative bacteria?

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

    What is the outcome of rinsing a Gram stain slide with ethanol?

    <p>It acts as a decolorizer</p> Signup and view all the answers

    What feature characterizes the colony elevation of Gram-positive bacteria?

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

    What is the description of 'Vibrio' bacteria?

    <p>Curved rod-shaped</p> Signup and view all the answers

    What is the primary goal of streaking for isolation in microbiology?

    <p>To separate individual bacterial colonies</p> Signup and view all the answers

    What is the effect of heat-fixing bacteria on a slide?

    <p>It kills bacteria and causes them to adhere to the slide</p> Signup and view all the answers

    What common error might occur during the streaking for isolation technique?

    <p>Not flaming the loop between streaks</p> Signup and view all the answers

    What can be inferred about the optimum growth temperature for different bacteria?

    <p>Optimum growth temperature varies between bacterial species</p> Signup and view all the answers

    Where are hydrophobic amino acids typically located in a polypeptide chain?

    <p>In the interior, away from water</p> Signup and view all the answers

    What is the result of the hemolysis test for the organism described?

    <p>Complete (beta) hemolysis</p> Signup and view all the answers

    Which bacterium characteristic is indicated by cells staining purple?

    <p>Gram positive bacteria</p> Signup and view all the answers

    What does a resistant reaction to the bacitracin test suggest?

    <p>No zone of clearance over 15mm</p> Signup and view all the answers

    Which antibiotic would the doctor prescribe given the sensitivity results?

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

    At what temperature range do mesophiles thrive?

    <p>12-45°C</p> Signup and view all the answers

    Which type of bacteria require high CO2 concentrations?

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

    What bacterial shape is described as rod-shaped?

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

    What is the result of the bile esculin test in this case?

    <p>None (gamma)</p> Signup and view all the answers

    Which bacteria are identified as coagulase positive bacteria?

    <p>Staphylococcus oculus and Staphylococcus aureus</p> Signup and view all the answers

    What is indicated by a negative coagulase reaction?

    <p>Both the control and test latex show no coagulation.</p> Signup and view all the answers

    Which bacteria is noted for often giving unreliable results on the coagulase test?

    <p>Enterococcus faecalis</p> Signup and view all the answers

    What further test can help identify bacteria that provide unreliable coagulase results?

    <p>Esculine test</p> Signup and view all the answers

    What does an unreliable coagulase reaction imply?

    <p>There is ambiguous reactivity in the test latex.</p> Signup and view all the answers

    What color should Gram-positive cells stain when the procedure is performed correctly?

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

    What result occurs if the decolorizer is forgotten while staining Gram-negative cells?

    <p>The cells stain purple</p> Signup and view all the answers

    Which of the following conditions can be diagnosed using the Kinyoun acid-fast stain?

    <p>Tuberculosis (TB)</p> Signup and view all the answers

    If the iodine step is omitted in the Gram staining process, what result is expected for Gram-positive cells?

    <p>They will stain pink or lighter</p> Signup and view all the answers

    What should happen to acid-fast cells in a Kinyoun stain?

    <p>They stain pink</p> Signup and view all the answers

    What does a positive result in a Bile Esculin Plate indicate?

    <p>Bacteria can hydrolyze esculin.</p> Signup and view all the answers

    What ingredient in MSA plates serves as a selective factor?

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

    What is a characteristic of a negative result in a Catalase Test?

    <p>No bubbles form.</p> Signup and view all the answers

    What is the advantage of the coagulase enzyme for bacteria?

    <p>It protects bacteria from the immune response.</p> Signup and view all the answers

    What indicates that bacteria can ferment mannitol on an MSA plate?

    <p>Appearance of yellow colonies.</p> Signup and view all the answers

    What is the role of a chromagen in microbiology?

    <p>It alters the color of cells.</p> Signup and view all the answers

    What is the purpose of conducting an antibiotic sensitivity test?

    <p>To guide the selection of effective antibiotics.</p> Signup and view all the answers

    Does Staphylococcus aureus change the color of the MSA media?

    <p>Yes, it changes the media to yellow.</p> Signup and view all the answers

    Which of the following describes what a carbon source does in microbiological media?

    <p>It produces energy for bacterial growth.</p> Signup and view all the answers

    What information does a doctor seek from an antibiotic sensitivity test?

    <p>The appropriate treatment with antibiotics.</p> Signup and view all the answers

    Which of the following bacteria is NOT tolerant to high salt concentrations?

    <p><em>Streptococcus pyogenes</em></p> Signup and view all the answers

    In microbiology, which of the following is true about a carbon source?

    <p>It can be used for metabolic processes.</p> Signup and view all the answers

    What is the expected result of Streptococcus pyogenes on blood agar?

    <p>Clear (beta-hemolysis)</p> Signup and view all the answers

    Why doesn't Staphylococcus epidermidis change the color of MSA media?

    <p>It does not ferment mannitol.</p> Signup and view all the answers

    What is being tested by observing the effects of hemolysin toxins on blood agar?

    <p>Destruction of red blood cells</p> Signup and view all the answers

    Study Notes

    Faulk Woodall's Microbiology Lab Notes

    • Gram-positive bacteria: stain purple.
    • Gram-negative bacteria: stain pink.
    • Catalase test: bubbles indicate a positive result; the enzyme catalase detoxifies free radical oxygen molecules.
    • Coagulase test: determines if bacteria produce coagulase, an enzyme that causes blood plasma to clot, protecting bacteria from the immune response.
    • Heat-fixing: kills bacteria and causes them to adhere to the slide.
    • Streaking for isolation: separates individual bacterial colonies.
    • Bacterial growth temperatures:
      • Psychrophiles: thrive in 0-20°C
      • Mesophiles: thrive in 12-45°C
      • Thermophiles: thrive at 40-70°C
    • Aerobes: need oxygen for ATP production.
    • Anaerobes: do not require oxygen for ATP production.
    • Capnophiles: need high CO2 concentrations.
    • Microaerophiles: need low oxygen concentrations.
    • Bacterial Shapes:
      • Cocci: round
      • Bacilli: rod-shaped
      • Vibrio: comma-shaped
      • Spirilla: spiral-shaped
    • MSA (Mannitol Salt Agar):
      • Staphylococcus aureus grows on MSA, ferments mannitol, and turns the media yellow.
      • Staphylococcus epidermidis grows on MSA but does not ferment mannitol, thus does not change the color of the media.
      • Streptococcus pyogenes does not grow on MSA because it is not tolerant to high salt concentrations.
    • Blood Agar Plate:
      • Streptococcus pyogenes causes beta-hemolysis (clear zone) on blood agar.
      • Enterococcus faecalis can cause alpha-hemolysis (partial clearing), gamma hemolysis (no clearing) or no reaction at all.
      • Strep. pyogenes causes beta-hemolysis (clear zone) on blood agar.
    • Bile Esculin Plate:
      • Selective ingredient: Bile
      • Differential ingredient: esculin
      • Positive result: Black agar.
      • Negative result: No change in appearance.
    • MSA Plate:
      • Selective ingredient: Salt.
      • Differential ingredient: Mannitol.
    • Gram Staining Procedure:
      • Gram-positive cells: expect purple staining.
      • Gram-negative cells: expect pink or red staining.
      • Potential Errors and Consequences:
        • Forgetting the decolorizer: False positive (purple stain) for both Gram-positive and Gram-negative cells.
        • Forgetting iodine: False negative (pink or clear) for both Gram-positive and Gram-negative cells.
        • Forgetting safranin: False negative (clear) for both Gram-positive and Gram-negative cells
    • Kinyoun Stain (Acid-Fast Staining): Acid-fast cells turn pink.
    • Antibiotic Sensitivity Test: Determines which antibiotics are effective against a particular bacterium, helping doctors prescribe the appropriate medication.

    Bacterial Infections and Diagnosis

    • Streptococcus pyogenes: Symptoms are common in the throat.
    • Staphylococcus aureus: Typically infects the skin, causing skin infections.
    • Tuberculosis (TB): Diagnosed using acid-fast staining.
    • Coagulase test: Staphylococcus oculus (likely a typo, it's Aureus) and Aureus have a positive reaction.
    • Enterococcus Faecalis: Often gives unreliable results on the coagulase test.
    • Dichotomous Key: A tool used for the identification of bacteria.

    Microbiology Lab Definitions:

    • Chromagen: A substance that changes the color of cells.
    • Antibiotic: Medication used to fight bacterial infections.
    • Carbon source: A substance that provides carbon sources for bacteria, such as MSA, sugars, and salts.

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    Description

    Test your knowledge on key concepts of microbiology, including the characteristics of Gram-positive and Gram-negative bacteria, different bacterial growth conditions, and essential lab techniques such as heat-fixing and the catalase test. This quiz covers various bacterial shapes and the requirements for different types of bacteria.

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