BIOD 171 Module 4 Exam Questions and
100 % Correct Answers Latest2025/2026
highly graded a+: Essential
Microbiology - Portage Learning
Alpha hemolysis - CORRECT ANSWERS--Presents with greenish-brown color on blood
agar due to the partial lysis of red blood cells
Beta hemolysis - CORRECT ANSWERS--Clear zones on blood agar indicate beta
hemolysis, which is the complete lysis of red blood cells
Gamma hemolysis - CORRECT ANSWERS--Presents a white/tan on blood agar due to
the lack of hemolytic activity.
What is the primary purpose of Columbia CNA agar? - CORRECT ANSWERS--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 ANSWERS--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
ANSWERS--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
ANSWERS--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 ANSWERS--Plating. Plating microbes can be done using a sterile loop, a
sterile swab, or a sterilized wire loop. Each device is simply a means of spreading the
bacteria, most commonly in a simple back-and-forth motion, across the plate.
, What is the primary advantage of plating a bacterial culture as opposed to having it
grow in solution? - CORRECT ANSWERS--The primary advantage of plating a bacterial
sample onto agar is that cells are held in place. Unlike in a nutrient broth where
bacterial cells can multiply but are free to move around in solution, bacteria plated onto
agar are fixed in such a way as to support the formation and visualization of colonies.
What is the purpose of the quadrant streak approach? - CORRECT ANSWERS--The
purpose of this method is to generate an individual colony so that a single (pure)
bacterial sample can be picked from the plate.
In a three-phase dilution gradient, which phase most likely contains individual colonies:
phase 1 (P1) or phase 3 (P3)? - CORRECT ANSWERS--Individual colonies are most
likely going to appear within the phase 3 streaks. You being with P1 (highest
concentration), dilute during P2 and then further dilute the sample in P3. However, it is
possible to see individual colonies in P2 if only a small portion of P1 was carried over
into P2.
What growth requirements are necessary for growth and survival? - CORRECT
ANSWERS--Nutrients, temperature, and pH
Photoautotrophs - CORRECT ANSWERS---Organisms that use light as a source of
energy and carbon dioxide as a source of carbon
-Plants, algae, cyanobacteria
Chemoautotrophs - CORRECT ANSWERS---Organisms that use chemicals as a source
of energy and carbon dioxide as a source of carbon
-Hydrogen, sulfur, and nitrifying bacteria, some archaea
Photoheterotrophs - CORRECT ANSWERS---Organisms that use light as a source of
energy and organic compounds as a source of carbon
-Green nonsulfur bacteria and purple nonsulfur bacteria, archaea
Chemoheterotrophs - CORRECT ANSWERS---Organisms that use chemical
compounds as a source of energy and organic compounds as a source of carbon
-Most animals, fungi, and protozoa and many bacteria
Toxic reactive oxygen species (ROS) - CORRECT ANSWERS---1O2, O2-, O2 2-, OH-
Obligate anaerobes - CORRECT ANSWERS--Organisms that cannot live where
molecular oxygen is present (so ROS is toxic)
Obligate aerobes - CORRECT ANSWERS--Organisms that contain enzymes and
antioxidants that protect from ROS
Facultative anaerobes - CORRECT ANSWERS---Organisms that live in environments
w/ or w/o oxygen
100 % Correct Answers Latest2025/2026
highly graded a+: Essential
Microbiology - Portage Learning
Alpha hemolysis - CORRECT ANSWERS--Presents with greenish-brown color on blood
agar due to the partial lysis of red blood cells
Beta hemolysis - CORRECT ANSWERS--Clear zones on blood agar indicate beta
hemolysis, which is the complete lysis of red blood cells
Gamma hemolysis - CORRECT ANSWERS--Presents a white/tan on blood agar due to
the lack of hemolytic activity.
What is the primary purpose of Columbia CNA agar? - CORRECT ANSWERS--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 ANSWERS--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
ANSWERS--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
ANSWERS--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 ANSWERS--Plating. Plating microbes can be done using a sterile loop, a
sterile swab, or a sterilized wire loop. Each device is simply a means of spreading the
bacteria, most commonly in a simple back-and-forth motion, across the plate.
, What is the primary advantage of plating a bacterial culture as opposed to having it
grow in solution? - CORRECT ANSWERS--The primary advantage of plating a bacterial
sample onto agar is that cells are held in place. Unlike in a nutrient broth where
bacterial cells can multiply but are free to move around in solution, bacteria plated onto
agar are fixed in such a way as to support the formation and visualization of colonies.
What is the purpose of the quadrant streak approach? - CORRECT ANSWERS--The
purpose of this method is to generate an individual colony so that a single (pure)
bacterial sample can be picked from the plate.
In a three-phase dilution gradient, which phase most likely contains individual colonies:
phase 1 (P1) or phase 3 (P3)? - CORRECT ANSWERS--Individual colonies are most
likely going to appear within the phase 3 streaks. You being with P1 (highest
concentration), dilute during P2 and then further dilute the sample in P3. However, it is
possible to see individual colonies in P2 if only a small portion of P1 was carried over
into P2.
What growth requirements are necessary for growth and survival? - CORRECT
ANSWERS--Nutrients, temperature, and pH
Photoautotrophs - CORRECT ANSWERS---Organisms that use light as a source of
energy and carbon dioxide as a source of carbon
-Plants, algae, cyanobacteria
Chemoautotrophs - CORRECT ANSWERS---Organisms that use chemicals as a source
of energy and carbon dioxide as a source of carbon
-Hydrogen, sulfur, and nitrifying bacteria, some archaea
Photoheterotrophs - CORRECT ANSWERS---Organisms that use light as a source of
energy and organic compounds as a source of carbon
-Green nonsulfur bacteria and purple nonsulfur bacteria, archaea
Chemoheterotrophs - CORRECT ANSWERS---Organisms that use chemical
compounds as a source of energy and organic compounds as a source of carbon
-Most animals, fungi, and protozoa and many bacteria
Toxic reactive oxygen species (ROS) - CORRECT ANSWERS---1O2, O2-, O2 2-, OH-
Obligate anaerobes - CORRECT ANSWERS--Organisms that cannot live where
molecular oxygen is present (so ROS is toxic)
Obligate aerobes - CORRECT ANSWERS--Organisms that contain enzymes and
antioxidants that protect from ROS
Facultative anaerobes - CORRECT ANSWERS---Organisms that live in environments
w/ or w/o oxygen
