BIOL 3201 (Micro Lab 3) Study Guide
and All Correct Answers 2026.
Selective medium - Answer media that will allow only certain microorganisms to grow and will
inhibit the growth of other microorganisms
what is mixed in to media to create selective conditions - Answer antibiotics, antifungals,
inhibitory compounds
the incorporation of _____ _____ into mannitol salt agar (MSA) selects for Staphylococcus but
inhibits the growth of bacteria that cannot tolerate the salt concentration - Answer sodium
chloride
differential medium - Answer contains substances that cause some bacteria to take on an
appearance that distinguishes them from othe rbacteria
When Staphylococcus aureus grows on _________________, it ferments mannitol producing
acid and changing a pH indicator in the media from what color to what color around the
colonies. - Answer mannitol salt agar (MSA), red to yellow
another differential medium - Answer sheep blood agar
beta hemolysis - Answer complete lysis of red blood cells around a colony. results in clear zone
surrounding the colonies
alpha hemolysis - Answer partial breakdown of red blood cells producing a greenish
discoloration around the colonies
gamma hemolysis - Answer species of bacteria that do not exhibit any hemolysis of blood
display
aerobic bacteria - Answer require oxygen for growth. produce water and hydrogen peroxide
(by-product)
do avoid the damage hydrogen peroxide does to aerobic bacteria, they produce what enzyme.
what does it do? - Answer catalase, degrades peroxide into water and oxygen
strict anaerobes - Answer bacteria that cannot grow in presence of oxygen
, aerotolerant bacteria - Answer anaerobes that tolerate oxygen
facultative anaerobes - Answer bacteria that can grow by respiration or fermentation, and
with or without oxygen (both produce catalase)
if an organism can break down carbohydrates by oxidation or fermentation, ____ is usually
produced - Answer acid
The presence of acid is indicated by a color change in the pH indicator, phenol red, from _____
at alkaline pH values to _____ at acidic pH values - Answer red, yellow
what are the two constituents of a starch macromolecule - Answer amylose, amylopectin
amylose - Answer straight chain polymer of 200-300 glucose molecules
bacteria that hydrolyze starch produce ______ that degrade starch molecules into maltose,
glucose, and dextrin molecules - Answer amylases
starch hydrolysis is detected who - Answer by adding gram's iodine to a starch agar plate
bile esculin agar - Answer selective and differential medium used to presumptively identify
Enterococcus and streptococcus based on ability of organism to hydrolyze esculin
when an organism hydrolyzes esculin, what's formed? which product reacts with ferric citrate to
turn medium dark brown or black - Answer esculetin and dextrose, esculetin
A test using bile esculin agar is only positive when? - Answer more than half the medium is
dark brown/black after incubation
what is the coagulase test good for - Answer confirming identification of S. aureus
The procedure is simple. It involves inoculating a small tube of blood plasma with a loopful of
the organism and incubating it in at 37°C for 24 hours. If the plasma coagulates (clots), the
organism produces coagulase and is considered coagulase positive. - Answer procedure for
coagulase test
and All Correct Answers 2026.
Selective medium - Answer media that will allow only certain microorganisms to grow and will
inhibit the growth of other microorganisms
what is mixed in to media to create selective conditions - Answer antibiotics, antifungals,
inhibitory compounds
the incorporation of _____ _____ into mannitol salt agar (MSA) selects for Staphylococcus but
inhibits the growth of bacteria that cannot tolerate the salt concentration - Answer sodium
chloride
differential medium - Answer contains substances that cause some bacteria to take on an
appearance that distinguishes them from othe rbacteria
When Staphylococcus aureus grows on _________________, it ferments mannitol producing
acid and changing a pH indicator in the media from what color to what color around the
colonies. - Answer mannitol salt agar (MSA), red to yellow
another differential medium - Answer sheep blood agar
beta hemolysis - Answer complete lysis of red blood cells around a colony. results in clear zone
surrounding the colonies
alpha hemolysis - Answer partial breakdown of red blood cells producing a greenish
discoloration around the colonies
gamma hemolysis - Answer species of bacteria that do not exhibit any hemolysis of blood
display
aerobic bacteria - Answer require oxygen for growth. produce water and hydrogen peroxide
(by-product)
do avoid the damage hydrogen peroxide does to aerobic bacteria, they produce what enzyme.
what does it do? - Answer catalase, degrades peroxide into water and oxygen
strict anaerobes - Answer bacteria that cannot grow in presence of oxygen
, aerotolerant bacteria - Answer anaerobes that tolerate oxygen
facultative anaerobes - Answer bacteria that can grow by respiration or fermentation, and
with or without oxygen (both produce catalase)
if an organism can break down carbohydrates by oxidation or fermentation, ____ is usually
produced - Answer acid
The presence of acid is indicated by a color change in the pH indicator, phenol red, from _____
at alkaline pH values to _____ at acidic pH values - Answer red, yellow
what are the two constituents of a starch macromolecule - Answer amylose, amylopectin
amylose - Answer straight chain polymer of 200-300 glucose molecules
bacteria that hydrolyze starch produce ______ that degrade starch molecules into maltose,
glucose, and dextrin molecules - Answer amylases
starch hydrolysis is detected who - Answer by adding gram's iodine to a starch agar plate
bile esculin agar - Answer selective and differential medium used to presumptively identify
Enterococcus and streptococcus based on ability of organism to hydrolyze esculin
when an organism hydrolyzes esculin, what's formed? which product reacts with ferric citrate to
turn medium dark brown or black - Answer esculetin and dextrose, esculetin
A test using bile esculin agar is only positive when? - Answer more than half the medium is
dark brown/black after incubation
what is the coagulase test good for - Answer confirming identification of S. aureus
The procedure is simple. It involves inoculating a small tube of blood plasma with a loopful of
the organism and incubating it in at 37°C for 24 hours. If the plasma coagulates (clots), the
organism produces coagulase and is considered coagulase positive. - Answer procedure for
coagulase test
