BIOD 171 Portage Learning Exam 4
Questions With Verified Answers
What is another name for a liquid growth media, what are the basic components? -
answer✔Nutrient broth. The basic components are sugar, amino acids, and vitamins.
What is selective media? - answer✔Selective media is when you only allow certain microbes to
grow while restricting the growth of the other microbes.
What is differential media? - answer✔Differential media is used to differentiate between two or
more related microbes.
What are the requirements of a fastidious media? - answer✔Fastidious media has complex
growth requirements. If it is absent, it will not grow.
What is agar? - answer✔It is a liquid growth media that has a hardening agent. It is used to allow
microbes to grow.
True or False: LB agar is classified as non-selective, differential media. - answer✔False
What are the three forms of hemolysis found on blood agar plates? - answer✔Alpha hemolysis:
Are greenish, brown due to incomplete lysis of red blood cells.
Beta hemolysis: Capacity of a microbe to completely lyse red blood cells. The resulting lysis
presents as a distinct zone of clearing around the growing colony
Gamma hemolysis: White/tan in color with red background.
What is the primary purpose of Columbia CNA agar? - answer✔It is sued to isolate Gram-
positive microbes.
Name the type of plate derived from BAP that contains lysed red blood cells. - answer✔Lysed
red blood cells.
Define the selective and differential abilities of a MacConkey agar plate. - answer✔It is selective
because it only allows Gram-negative microbes to grow. It is differential because it is capable of
distinguishing between microbes capable of fermenting lactose and those that don't.
What colors would you expect to see on an EMB plate containing E. coli.? - answer✔A green
sheen.
What is the name of the process of spreading a bacterial culture onto a Petri dish? -
answer✔Plating.
What is the primary advantage of plating a bacterial culture as opposed to having it grow in
solution? - answer✔The advantage is that it holds the cells in place.
What is the purpose of the quadrant streak approach? - answer✔To generate an individual colony
so a single pure culture can be picked.
In a three-phased dilution gradient, which phase most likely contains individual colonies: phase 1
or phase 3? - answer✔Phase 3 streaks.
A
Sorbitol- MacConkey Agar: PINK, TO detect the presence of the pathogenic strain or E.coli.
Eosin Methylene Blue Agar: is dark red in color and is selective and differential. Contains eosin
and meth. blue.
Mannitol Salt Agar: red in color and both selective and differential media. - answer✔LB Agar:
Are pale yellow, non selective and non differential. Commonly used for growing E.coli.
Trypticase Soy Agar: Same color as LB Agar (yellow pale) It is non selective and non
differential. Serves as the base/
Blood Agar: Red color, non selective yet differential media. Detects hemolysis. Streptococcus.
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