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Microbiology Lab Exam 2 (SCSU) questions well answered graded A+
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Microbiology Lab Exam 2 (SCSU) questions well answered graded A+
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Microbiology Lab Exam 2 (SCSU)Selective Media - correct answer ✔✔A selective media selects for one group of species and inhibits the
growth of all others
Differential Media - correct answer ✔✔allows for someone to differentiate between two or more
species and inhibits the growth of all others.
Enriched Media - correct answer ✔✔contains chemical nutrients to support the growth of organisms
with complex nutritional requirements.
Pure Culture - correct answer ✔✔a culture containing a single kind of organism free from other
organisms.
Mannitol Salt Agar(MSA) - correct answer ✔✔-Is both selective and differential
-Selective because it only allows growth of Staph species.
- It inhibits all other because it contains a high amount of sodium chloride which makes it hospitable for
salt- intolerant species
-Is differential because it can distinguish between mannitol fermenters and non fermenters
Phenylethyl alcohol agar(PEA) - correct answer ✔✔Is a selective Media
Selective because it selects for gram(+) and inhibits gram(-)
-Phenylethyl alcohol interferes with DNA replication and destorys the plasma membrane of gram (-)
bacteria.
-Gram (-) die at low concentrations of phenylethyl
-gram (+) can tolerate higher concentrations of Phenylethyl alcohol
MacConkey Agar - correct answer ✔✔Is Selective and Differential
-Selective for some gram (-) bacteria and inhibit the growth of all gram(+) and some gram(-)
- Differential
-The gram(-) that survive are differentiated based on their ability to ferment lactose.
, (The media is selective because of the bile salts and crystal violet)
-Fermentation of lactose will lower the ph of the medium and cause it change to a pink to red color.
Eosin Methylene Blue (EMB) - correct answer ✔✔Is a partially selective and differential media
-Selective for Gram (-) bacteria and inhibit gram(+)
-Differentiates on the gram(-) bacteria's ability to ferment lactose.
-If a microbe is capable of fermenting lactose it will turn a purple color
-E.coil when on a EMB agar will turn green due to contain large amounts of lactose
Tryptic Soy Agar - correct answer ✔✔is not selective or differential
-allows the grow of all species of organisms both gram(+) and gram(-)
Questions - correct answer ✔✔
phenylethyl alcohol agar(PEA) is considered a selective media. Describe the chemical features that make
the PEA agar selective for gram(+) cell survival. - correct answer ✔✔selective for gram(+) bacteria
because they can tolerate high and low concentrations of phenylethyl alcohol .
Why is PEA not considered a differential media? - correct answer ✔✔Not considered a differential media
because it only allows growth of gram(+) bacteria and inhibits the growth of gram(-)
What is the selective agent in the MacConkey agar that inhibits the growth of gram(+) organisms? -
correct answer ✔✔The selective agents are bile salts and crystal violet that inhibit the growth of gram
(+)
What would be the best agar to use to identify E.coli? - correct answer ✔✔The best agar would be the
EMB agar because E.coli forms a green color when put onto this plate, making it easy to identify
Explain why EMB is a differential and selective media - correct answer ✔✔its differential because it
differentiates lactose fermentation
Its a selective media because it inhibits the growth gram(+) and allows the growth of gram(-)
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