Microbio Lab Exam 1 Flashcards
What is the purpose of saffron in the Gram stain?
Stained gram-negative bacteria, pink/red
What is the purpose of crystal violet in the Gram stain?
Colors purple
Differentiating, gram-negative, and positive bacteria based on cell wall structures
What is the purpose of Grams iodine in the gram stain?
Act as a mordant
What is the purpose of the decolorizer/ethanol in the Gram stain?
Dissolves outer lipid layer of gram-negative cell, allowing crystal violet stain to wash out
What color are gram-positive cells after the Gram stain?
Purple/blue
What color are gram-negative cells after the gram stain
Pink/red
What is a mordant
Of fixative the combines with a dye/stain to intensify colorfastness
What is peptidoglycan made of?
Peptide + sugars
AA + NAM + NAG CHAINS CROSS, LINKED BY AA
What is the catalyze test test testing for?
What indicates a positive or negative result
Testing for presence of enzyme catalyze
Positive is immediate and visible bubbling
Negative is no bubbling
What is the oxidase test testing for?
What indicates a positive or negative result
Bacteria that have cytochrome C oxidase vs not.
Positive results react to reagent, turning purple or blue
Negative reacts with no color change
What is MR-VP Test testing for
Determines the type of glucose fermentation, a bacterium uses
What does a positive result for MR look like? What does it indicate?
Positive= Red color in MR test
Indicates mixed acid fermentation
What does a positive result for VP look like? What does it indicate?
Positive = Pink/red color
Presence of acetoin
What does growth on mannitol salt agar indicate
Bacteria can ferment mannitol
What changes color on mannitol salt if the bacteria ferment mannitol?
Red ——> yellow
Acid production
What does TSI stand for?
Triple sugar iron
What does a yellow base in the TSI indicate
Acid production
What does a red base in the TSI indicate?
No fermentation of glucose, lactose, sucrose. Instead metabolizes, peptones and indicates alkaline reaction.
What does a yellow slant in the TSI indicate?
Fermentation of either glucose, lactose, sucrose
What does a red slant in the TSI indicate?
Alkaline reaction
What are the three colors of bromothymol blue and what does each indicate?
Yellow – acidic
Green – neutral
Blue – basic
What are the three colors of phenol red? And what does each indicate
Yellow – acidic
Red – neutral
Pink – alkaline
What does the thioglycolate test show?
Oxygen requirements
Identifying aerobic or anaerobic
What is the site rate test test testing for? What indicates a positive result or a negative result.
Identifies gram-negative pathogens
Positive – green —-> blue
Negative - no growth or color change
