EXAM 1 INTRO TO CLINICAL MICROBIOLOGY
1. What are the key differences between eukaryotes and prokaryotes?
Answer Eukaryotes- (Algae, fungi, protozoa) enclosed in a nuclear membrane, membrane-bound organelles
Prokaryotes- (bacteria) have a cell wall, don't have membrane-bound organelles
2. How do you correctly write an organism name using binomial nomenclature?-
Answer The first name is capitalized, the second is lowercase, and both genus and species are written. Example
: Streptococcus
pyogenes.
3. What is the principle of the gram stain?
Answer Place a drop of sterile water on a dry slide, with a sterile loop, pick up a little bit and mix the water.
After the slide is dry, fix with methanol over the sink for 1 minute. Note heat fixing the slide will distort the specimen. Rinse.
Add crystal violet to the slide for 1 minute; this is the primary stain. It penetrates the cell wall and stains all bacteria purple. Raise.
Add Iodine for 1 minute; this is a mordant it enhances the reaction between the cell wall and the primary stain, making a complex.
Rinse.
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,Add a decolorizer like ethyl/acetone, which damages the outer membrane if the Gram-negative cells, then the peptidoglycan layer is
exposed. Rinse immediately or you will -decolorize.
Add Safranin for 30 seconds, which is a counterstain; this will color the gram-negative cells pink. Raise then pat dry and air dry, read
them at 100x oil immersion.
4. Nonselective- supports growth of most nonfastidious organisms. Ex.BAP
Answer -
supports growth of most nonfastidious organisms. Ex.BAP
5. Differential- allow grouping of organisms by their ability to demonstrate phenotypic
differences on the agar. Ex. BAP
Answer - allow grouping of organisms by their ability to demonstrate phenotypic ditterences on the agar. Ex. BAP
6. Selective
Answer - allow grouping of one organism but not another.
7. What are the atmospheric requirements of aerobes?
Answer Aerobes grow in ambient air (78%
nitrogen, 21% oxygen, 1% other gases).
8. Enriched
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, Answer - nonselective media that include additional growth enhancers to allow fastidious organisms to grow. Ex. CHOC.
9. obligate aerobes
Answer - requires oxygen
10. obligate anaerobes
Answer - cannot grow in the presence oxygen
11. facultative anaerobes
Answer - can grow with/without the presence of oxygen
12. Microaerophiles- requires small amounts to grow
Answer - requires small amounts to grow
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1. What are the key differences between eukaryotes and prokaryotes?
Answer Eukaryotes- (Algae, fungi, protozoa) enclosed in a nuclear membrane, membrane-bound organelles
Prokaryotes- (bacteria) have a cell wall, don't have membrane-bound organelles
2. How do you correctly write an organism name using binomial nomenclature?-
Answer The first name is capitalized, the second is lowercase, and both genus and species are written. Example
: Streptococcus
pyogenes.
3. What is the principle of the gram stain?
Answer Place a drop of sterile water on a dry slide, with a sterile loop, pick up a little bit and mix the water.
After the slide is dry, fix with methanol over the sink for 1 minute. Note heat fixing the slide will distort the specimen. Rinse.
Add crystal violet to the slide for 1 minute; this is the primary stain. It penetrates the cell wall and stains all bacteria purple. Raise.
Add Iodine for 1 minute; this is a mordant it enhances the reaction between the cell wall and the primary stain, making a complex.
Rinse.
1/
19
,Add a decolorizer like ethyl/acetone, which damages the outer membrane if the Gram-negative cells, then the peptidoglycan layer is
exposed. Rinse immediately or you will -decolorize.
Add Safranin for 30 seconds, which is a counterstain; this will color the gram-negative cells pink. Raise then pat dry and air dry, read
them at 100x oil immersion.
4. Nonselective- supports growth of most nonfastidious organisms. Ex.BAP
Answer -
supports growth of most nonfastidious organisms. Ex.BAP
5. Differential- allow grouping of organisms by their ability to demonstrate phenotypic
differences on the agar. Ex. BAP
Answer - allow grouping of organisms by their ability to demonstrate phenotypic ditterences on the agar. Ex. BAP
6. Selective
Answer - allow grouping of one organism but not another.
7. What are the atmospheric requirements of aerobes?
Answer Aerobes grow in ambient air (78%
nitrogen, 21% oxygen, 1% other gases).
8. Enriched
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19
, Answer - nonselective media that include additional growth enhancers to allow fastidious organisms to grow. Ex. CHOC.
9. obligate aerobes
Answer - requires oxygen
10. obligate anaerobes
Answer - cannot grow in the presence oxygen
11. facultative anaerobes
Answer - can grow with/without the presence of oxygen
12. Microaerophiles- requires small amounts to grow
Answer - requires small amounts to grow
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