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Questions and Answers
What is required for bacteria to perform fermentation?
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?
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?
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?
Why do smaller wavelengths provide better resolution in microscopy?
What does the enzyme catalase do?
What does the enzyme catalase do?
What is the first step in the Gram stain procedure?
What is the first step in the Gram stain procedure?
Which type of bacteria is described as having a thick peptidoglycan layer?
Which type of bacteria is described as having a thick peptidoglycan layer?
Which shape is described as spiral-shaped and flexible?
Which shape is described as spiral-shaped and flexible?
What indicates that Streptococcus pneumoniae is susceptible to Bacitracin?
What indicates that Streptococcus pneumoniae is susceptible to Bacitracin?
Which option describes the colony margin of Gram-negative bacteria?
Which option describes the colony margin of Gram-negative bacteria?
What is the outcome of rinsing a Gram stain slide with ethanol?
What is the outcome of rinsing a Gram stain slide with ethanol?
What feature characterizes the colony elevation of Gram-positive bacteria?
What feature characterizes the colony elevation of Gram-positive bacteria?
What is the description of 'Vibrio' bacteria?
What is the description of 'Vibrio' bacteria?
What is the primary goal of streaking for isolation in microbiology?
What is the primary goal of streaking for isolation in microbiology?
What is the effect of heat-fixing bacteria on a slide?
What is the effect of heat-fixing bacteria on a slide?
What common error might occur during the streaking for isolation technique?
What common error might occur during the streaking for isolation technique?
What can be inferred about the optimum growth temperature for different bacteria?
What can be inferred about the optimum growth temperature for different bacteria?
Where are hydrophobic amino acids typically located in a polypeptide chain?
Where are hydrophobic amino acids typically located in a polypeptide chain?
What is the result of the hemolysis test for the organism described?
What is the result of the hemolysis test for the organism described?
Which bacterium characteristic is indicated by cells staining purple?
Which bacterium characteristic is indicated by cells staining purple?
What does a resistant reaction to the bacitracin test suggest?
What does a resistant reaction to the bacitracin test suggest?
Which antibiotic would the doctor prescribe given the sensitivity results?
Which antibiotic would the doctor prescribe given the sensitivity results?
At what temperature range do mesophiles thrive?
At what temperature range do mesophiles thrive?
Which type of bacteria require high CO2 concentrations?
Which type of bacteria require high CO2 concentrations?
What bacterial shape is described as rod-shaped?
What bacterial shape is described as rod-shaped?
What is the result of the bile esculin test in this case?
What is the result of the bile esculin test in this case?
Which bacteria are identified as coagulase positive bacteria?
Which bacteria are identified as coagulase positive bacteria?
What is indicated by a negative coagulase reaction?
What is indicated by a negative coagulase reaction?
Which bacteria is noted for often giving unreliable results on the coagulase test?
Which bacteria is noted for often giving unreliable results on the coagulase test?
What further test can help identify bacteria that provide unreliable coagulase results?
What further test can help identify bacteria that provide unreliable coagulase results?
What does an unreliable coagulase reaction imply?
What does an unreliable coagulase reaction imply?
What color should Gram-positive cells stain when the procedure is performed correctly?
What color should Gram-positive cells stain when the procedure is performed correctly?
What result occurs if the decolorizer is forgotten while staining Gram-negative cells?
What result occurs if the decolorizer is forgotten while staining Gram-negative cells?
Which of the following conditions can be diagnosed using the Kinyoun acid-fast stain?
Which of the following conditions can be diagnosed using the Kinyoun acid-fast stain?
If the iodine step is omitted in the Gram staining process, what result is expected for Gram-positive cells?
If the iodine step is omitted in the Gram staining process, what result is expected for Gram-positive cells?
What should happen to acid-fast cells in a Kinyoun stain?
What should happen to acid-fast cells in a Kinyoun stain?
What does a positive result in a Bile Esculin Plate indicate?
What does a positive result in a Bile Esculin Plate indicate?
What ingredient in MSA plates serves as a selective factor?
What ingredient in MSA plates serves as a selective factor?
What is a characteristic of a negative result in a Catalase Test?
What is a characteristic of a negative result in a Catalase Test?
What is the advantage of the coagulase enzyme for bacteria?
What is the advantage of the coagulase enzyme for bacteria?
What indicates that bacteria can ferment mannitol on an MSA plate?
What indicates that bacteria can ferment mannitol on an MSA plate?
What is the role of a chromagen in microbiology?
What is the role of a chromagen in microbiology?
What is the purpose of conducting an antibiotic sensitivity test?
What is the purpose of conducting an antibiotic sensitivity test?
Does Staphylococcus aureus change the color of the MSA media?
Does Staphylococcus aureus change the color of the MSA media?
Which of the following describes what a carbon source does in microbiological media?
Which of the following describes what a carbon source does in microbiological media?
What information does a doctor seek from an antibiotic sensitivity test?
What information does a doctor seek from an antibiotic sensitivity test?
Which of the following bacteria is NOT tolerant to high salt concentrations?
Which of the following bacteria is NOT tolerant to high salt concentrations?
In microbiology, which of the following is true about a carbon source?
In microbiology, which of the following is true about a carbon source?
What is the expected result of Streptococcus pyogenes on blood agar?
What is the expected result of Streptococcus pyogenes on blood agar?
Why doesn't Staphylococcus epidermidis change the color of MSA media?
Why doesn't Staphylococcus epidermidis change the color of MSA media?
What is being tested by observing the effects of hemolysin toxins on blood agar?
What is being tested by observing the effects of hemolysin toxins on blood agar?
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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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