ASU MIC 205 PENTON EXAM 1 QUESTIONS WITH CORRECT ANSWERS.
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ASU MIC 205
Institution
ASU MIC 205
ASU MIC 205 PENTON EXAM 1 QUESTIONS WITH CORRECT ANSWERS.ASU MIC 205 PENTON EXAM 1 QUESTIONS WITH CORRECT ANSWERS.ASU MIC 205 PENTON EXAM 1 QUESTIONS WITH CORRECT ANSWERS.ASU MIC 205 PENTON EXAM 1 QUESTIONS WITH CORRECT ANSWERS.ASU MIC 205 PENTON EXAM 1 QUESTIONS WITH CORRECT ANSWERS.ASU MIC 205 PE...
ASU MIC 205 PENTON EXAM 1
QUESTIONS WITH CORRECT ANSWERS.
What is the difference between a simple and differential stain?
-Simple: bacteria differ chemically from inner surroundings and thus can be stained to
contrast with their environment
-Differential: detects peptidoglycan, can distinguish between two bacteria
What does a Gram stain detect?
differences in the composition of the cell wall (i.e. peptidoglycan)
How does a gram stain differentiate bacterial cells?
by dying them a different color
What color is a Gram-positive organism?
purple
What color is a Gram-negative organism?
pink/red
What are the principle differences between a gram negative and gram positive
bacterial cell?
gram + has a thicker layer of peptidoglycan and no outer membrane
- Gram + cells have Techoic Acids
-Antigenic determinants
-Species identification
-Some (e.g. Mycobacterium) have Mycolic Acid (tuberculum): waxy lipid, survive
dessication, difficult to stain (acid-fast stain)
gram - has a thinner layer of peptidoglycan and an outer membrane, Gram - have an
outer bilayer membrane
Outer portion is composed of lipopolysaccharide (LPS) lipid+sugar
Outer membrane allows for survival in harsh environments
The outer sugar portion is called the O antigen, an antigenic determinant.
Lipid portion of LPS is called Lipid A, an Endotoxin (e.g. E. coli)
Dead cells release lipid A, trigger fever, inflammation, shock, blood clotting
What do penicillin antibiotics act on with the bacterial cell?
peptidoglycan layer
Are gram + or gram - bacteria more susceptible to penicillin antibiotics? Why
don't they harm eukaryotes?
Gram - are usually harder to treat due to the outer membrane
(many antibiotics target peptidoglycan layer-penicillin) making gram + more susceptible
to penicillin than gram -
What does an acid-fast stain detect?
differentiates cells with a waxy cell wall that contain high amounts of mycolic acid (ex;
mycobacterium and nocardia)
What color are acid-fast organisms after staining with an acid-fast stain?
red
How does an acid-fast stain differentiate bacterial cells?
, makes them appear red
Name an acid-fast organism.
Mycobacterium
Nocardia
Is a Schaeffer-Fulton stain a differential stain or a simple stain?
differential stain because the malachite green must be driven with heat to penetrate cell
walls because they are impermeable to almost all chemicals
In a Schaeffer-Fulton stain, what has to be done to the proteins in the cell
membrane in order to drive the primary stain into the endospore?
uses heat to drive the primary stain, malachite green, into the endospore
What is an endospore?
a dormant, tough, and temporarily non-reproductive structure produced by certain
bacteria.
Why do bacteria make endospores?
to survive in unfavorable enviorments
What bacterial group discussed in class is medically important and form
endospores? How does this relate to C. diff?
Bacillus is a type of bacteria that has endospores, which is a concern for food
processors. healthcare because it is resistant to treatment C. diff is a spore-forming G+
anaerobic bacillus and produces 2 exotoxins. --> 2 toxins : toxin A and toxin B--
colonoscopies
What does it mean for a bacterial growth medium to be selective?
Selective bacterial growth medium of every bacteria except the bacteria that will grow
on it.
What does it mean for a bacterial growth medium to be differential?
allows the different bacteria to be differentiated.
if a bacteria can use the nutrients in the substrate, an indicator will change the color and
allow you to tell what specific strain of bacteria it is
blood is not selective
Understand the selective and differential aspects of MacConkey's agar (MAC)
isolates the gram negative and enteric bacteria
differentiates them based on lactose fermentation
What information does MacConkey's agar provide about bacteria growing on this
medium?
Lac+ produce lactic acid, lowers the pH, changing
the colonies to pink (due to a pH indicator-neutral
red)
Lac - do not ferment lactose, no lactic acid
produced, white
Understand the selective and differential aspects of Mannitol Salt agar (MSA).
high salt (7.5%)- selective
mannitol- differential
What information does MSA provide about bacteria growing on this medium?
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