BIOD 171 Module 4 Exam UPDATED
ACTUAL Exam Questions and CORRECT
Answers
What is another name for a liquid growth media, and what are the basic components? -
CORRECT ANSWER - Growth media in a liquid form is often referred to as nutrient
broth. As the name implies its composition consists primarily of essential 'ingredients' such as a
rich source of sugars, amino acids, and vitamins. Together, a nutrient broth provides the microbe
with a source of carbon/energy, which, in turn, encourages its expansion.
What is selective media? - CORRECT ANSWER - Selective media allows for only the
growth of certain microbes while restricting the growth of all others.
What is differential media? - CORRECT ANSWER - Differential media is used to
distinguish between two (or more) related microbes.
What are the requirements of a fastidious microbe? - CORRECT ANSWER - A fastidious
microbe is an organism with complex growth requirements such that if absent it will not grow.
Enriched medias thus contain these specific and essential nutrients required for the growth of a
particular subset of microorganisms.
What is agar? - CORRECT ANSWER - In its simplest form agar is liquid growth media
that has had a hardening agent added to it. Agar is created when a polysaccharide derived from
seaweed (algae) extract is added to growth media. Agar is used to create a solid, smooth surface
on which microbes can grow.
LB agar is classified as a non-selective, differential media
True
False - CORRECT ANSWER - False
LB agar is non-selective and non-differential
, What are the three forms of hemolysis found on blood agar plates? - CORRECT
ANSWER - Alpha hemolysis, beta hemolysis, and gamma hemolysis
Alpha hemolysis - CORRECT ANSWER - Presents with greenish-brown color on blood
agar due to the partial lysis of red blood cells
Beta hemolysis - CORRECT ANSWER - Clear zones on blood agar indicate beta
hemolysis, which is the complete lysis of red blood cells
Gamma hemolysis - CORRECT ANSWER - Presents a white/tan on blood agar due to the
lack of hemolytic activity.
What is the primary purpose of Columbia CNA agar? - CORRECT ANSWER - As it
suppresses the growth of Gram-negative bacteria CNA agar is, therefore, used for isolation of
Gram-positive microbes.
Name the type of plate derived from BAP that contains lysed red blood cells - CORRECT
ANSWER - Lysed red blood cells (RBCs) are a primary component in the formulation of
Chocolate agar.
Define the selective and differential abilities of a MacConkey agar plate - CORRECT
ANSWER - MacConkey agar is selective in that only Gram-negative microbes will grow
on the agar -Gram-positive microbes simply do not grow. MacConkey agar is also considered a
differential media as it distinguishes between microbes capable of fermenting lactose (red
colonies) and those that are non-fermenters (white/tan colonies).
What colors would you expect to see on an EMB plate containing E. coli? - CORRECT
ANSWER - The EMB plate itself is red in color while in the presence of E. coli, the
growing colonies will take on a distinctive metallic green sheen.
What is the name of the process of spreading a bacterial culture onto a petri dish? - CORRECT
ANSWER - Plating. Plating microbes can be done using a sterile loop, a sterile swab, or a
ACTUAL Exam Questions and CORRECT
Answers
What is another name for a liquid growth media, and what are the basic components? -
CORRECT ANSWER - Growth media in a liquid form is often referred to as nutrient
broth. As the name implies its composition consists primarily of essential 'ingredients' such as a
rich source of sugars, amino acids, and vitamins. Together, a nutrient broth provides the microbe
with a source of carbon/energy, which, in turn, encourages its expansion.
What is selective media? - CORRECT ANSWER - Selective media allows for only the
growth of certain microbes while restricting the growth of all others.
What is differential media? - CORRECT ANSWER - Differential media is used to
distinguish between two (or more) related microbes.
What are the requirements of a fastidious microbe? - CORRECT ANSWER - A fastidious
microbe is an organism with complex growth requirements such that if absent it will not grow.
Enriched medias thus contain these specific and essential nutrients required for the growth of a
particular subset of microorganisms.
What is agar? - CORRECT ANSWER - In its simplest form agar is liquid growth media
that has had a hardening agent added to it. Agar is created when a polysaccharide derived from
seaweed (algae) extract is added to growth media. Agar is used to create a solid, smooth surface
on which microbes can grow.
LB agar is classified as a non-selective, differential media
True
False - CORRECT ANSWER - False
LB agar is non-selective and non-differential
, What are the three forms of hemolysis found on blood agar plates? - CORRECT
ANSWER - Alpha hemolysis, beta hemolysis, and gamma hemolysis
Alpha hemolysis - CORRECT ANSWER - Presents with greenish-brown color on blood
agar due to the partial lysis of red blood cells
Beta hemolysis - CORRECT ANSWER - Clear zones on blood agar indicate beta
hemolysis, which is the complete lysis of red blood cells
Gamma hemolysis - CORRECT ANSWER - Presents a white/tan on blood agar due to the
lack of hemolytic activity.
What is the primary purpose of Columbia CNA agar? - CORRECT ANSWER - As it
suppresses the growth of Gram-negative bacteria CNA agar is, therefore, used for isolation of
Gram-positive microbes.
Name the type of plate derived from BAP that contains lysed red blood cells - CORRECT
ANSWER - Lysed red blood cells (RBCs) are a primary component in the formulation of
Chocolate agar.
Define the selective and differential abilities of a MacConkey agar plate - CORRECT
ANSWER - MacConkey agar is selective in that only Gram-negative microbes will grow
on the agar -Gram-positive microbes simply do not grow. MacConkey agar is also considered a
differential media as it distinguishes between microbes capable of fermenting lactose (red
colonies) and those that are non-fermenters (white/tan colonies).
What colors would you expect to see on an EMB plate containing E. coli? - CORRECT
ANSWER - The EMB plate itself is red in color while in the presence of E. coli, the
growing colonies will take on a distinctive metallic green sheen.
What is the name of the process of spreading a bacterial culture onto a petri dish? - CORRECT
ANSWER - Plating. Plating microbes can be done using a sterile loop, a sterile swab, or a
