4/27/25, 11:15 bio 229 exam 2 |
AM
BIO 229 EXAM 2 EXAM QUESTIONS AND ANSWERS WITH COMPLETE
SOLUTIONS VERIFIED GRADED A++
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Terms in this set (96)
Selective:
➢ Gram +
➢ Colistin (disrupts cytoplasmic
membrane of Gram -) &
Nalidixic acid (prevents DNA
replication in Gram -)
Differential:
Colombia CNA w/ 5% ➢ Sheep's blood
Sheep Blood Agar differentiates organisms
based on hemolysis
patterns
● Types:
○ B-hemolysis:
colonies surrounded
by white/clear zone
no blood cells
○ A-hemolysis: zone of intact but
discolored blood cells (green/brown)
○ Y-hemolysis:
microbes lyse cells =
no change in
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,4/27/25, 11:15 bio 229 exam 2 |
AM
medium
Selective:
➢ Gram -
➢ Crystal Violet and bile salts inhibit Gram +
Differential:
➢ Lactose fermentation
visualized by neutral red
MacConkey Agar indicator
● If organism ferments lactose, acidic
by-products build up & pH
around colony drops causing
the colony to absorb
indicator
○ Results in pink to brick-red colonies
● If organism does not
ferment lactose, will
remain translucent
2/35
,4/27/25, 11:15 bio 229 exam 2 |
AM
Selective:
➢ Halophiles
➢ Contains 7.5% NaCl
Differential:
➢ Mannitol fermentation
Mannitol Salt Agar visualized by phenol red
indicator
● If organism ferments
mannitol, resulting acids
lower pH of medium
causing pH indicator to
change from red to
yellow
● If organism does not
ferment mannitol, will
remain translucent
○ Defined: all components & amounts known
○ Complex: not all components are known, will
support growth of most organisms
● Selective vs. Nonselective:
Differences between ○ "Selects" for growth of some organisms inhibits
Complex media, growth of others
selective media, &
selective & differential ● Differential vs. Non Differential:
○ "Differentiates" microbes based on metabolic
media
activity
● Selective & Differential:
○ Selects for and differentiates
between organisms based on
organism's ability to grow
under selective conditions
Discuss biochemical a thick layer that adheres tightly to
makeup of a capsule organisms composed of polysaccharide,
polypeptide, or both
3/35
, 4/27/25, 11:15 bio 229 exam 2 |
AM
○ Form of Glycocalyx- protects organisms
Describe how the from drying out and retain nutrients for
presence of the
organisms
capsule contributes
○ Capsule- protects bacteria from immune
to an organism's
response of host; primary determinant of
potential
pathogenicity virulence-relative ability of a bacterium to
cause disease;
helps provide immunological disguise for
organisms when in human body; can
facilitate attachment
View a capsule stain of a Visible as halos around bacteria; difficult to
bacterial culture stain because of their solubility in water
○ Capsule- composed of chemicals similar
to host; allows bacteria to attach to various
surfaces
Differentiate between
○ Slim layer(only found in bacteria)- loosely
capsular material and
attached to cell and to allow bacteria to
bacterial cell itself
adhere to objects; protects cell from drying
out, trap nutrients ,
& helps formation of biofilms
○ Bacteria- encased in capsules/ slim layer
and forms micro colonies attached to
surfaces which are apart of biofilms
● Gram +
Discuss what makes an ● Cell walls composed of mostly mycolic acids
organism acid-fast & ● Mycolic acids:
the Gram -Are long fatty acids
classification of acid- -Create barrier to hydrophilic molecules
fast
organisms
Cell Wall Composition:
○ Mycolic acids are closely packed in a monolayer
○ Has a low permeability
Explain the ● Impact on Virulence:
composition of the cell ○ Mycolic lipids are "waxy"
wall in acid fast protecting them from antibiotics &
4/35
AM
BIO 229 EXAM 2 EXAM QUESTIONS AND ANSWERS WITH COMPLETE
SOLUTIONS VERIFIED GRADED A++
Leave the first rating
Save
Terms in this set (96)
Selective:
➢ Gram +
➢ Colistin (disrupts cytoplasmic
membrane of Gram -) &
Nalidixic acid (prevents DNA
replication in Gram -)
Differential:
Colombia CNA w/ 5% ➢ Sheep's blood
Sheep Blood Agar differentiates organisms
based on hemolysis
patterns
● Types:
○ B-hemolysis:
colonies surrounded
by white/clear zone
no blood cells
○ A-hemolysis: zone of intact but
discolored blood cells (green/brown)
○ Y-hemolysis:
microbes lyse cells =
no change in
1/35
,4/27/25, 11:15 bio 229 exam 2 |
AM
medium
Selective:
➢ Gram -
➢ Crystal Violet and bile salts inhibit Gram +
Differential:
➢ Lactose fermentation
visualized by neutral red
MacConkey Agar indicator
● If organism ferments lactose, acidic
by-products build up & pH
around colony drops causing
the colony to absorb
indicator
○ Results in pink to brick-red colonies
● If organism does not
ferment lactose, will
remain translucent
2/35
,4/27/25, 11:15 bio 229 exam 2 |
AM
Selective:
➢ Halophiles
➢ Contains 7.5% NaCl
Differential:
➢ Mannitol fermentation
Mannitol Salt Agar visualized by phenol red
indicator
● If organism ferments
mannitol, resulting acids
lower pH of medium
causing pH indicator to
change from red to
yellow
● If organism does not
ferment mannitol, will
remain translucent
○ Defined: all components & amounts known
○ Complex: not all components are known, will
support growth of most organisms
● Selective vs. Nonselective:
Differences between ○ "Selects" for growth of some organisms inhibits
Complex media, growth of others
selective media, &
selective & differential ● Differential vs. Non Differential:
○ "Differentiates" microbes based on metabolic
media
activity
● Selective & Differential:
○ Selects for and differentiates
between organisms based on
organism's ability to grow
under selective conditions
Discuss biochemical a thick layer that adheres tightly to
makeup of a capsule organisms composed of polysaccharide,
polypeptide, or both
3/35
, 4/27/25, 11:15 bio 229 exam 2 |
AM
○ Form of Glycocalyx- protects organisms
Describe how the from drying out and retain nutrients for
presence of the
organisms
capsule contributes
○ Capsule- protects bacteria from immune
to an organism's
response of host; primary determinant of
potential
pathogenicity virulence-relative ability of a bacterium to
cause disease;
helps provide immunological disguise for
organisms when in human body; can
facilitate attachment
View a capsule stain of a Visible as halos around bacteria; difficult to
bacterial culture stain because of their solubility in water
○ Capsule- composed of chemicals similar
to host; allows bacteria to attach to various
surfaces
Differentiate between
○ Slim layer(only found in bacteria)- loosely
capsular material and
attached to cell and to allow bacteria to
bacterial cell itself
adhere to objects; protects cell from drying
out, trap nutrients ,
& helps formation of biofilms
○ Bacteria- encased in capsules/ slim layer
and forms micro colonies attached to
surfaces which are apart of biofilms
● Gram +
Discuss what makes an ● Cell walls composed of mostly mycolic acids
organism acid-fast & ● Mycolic acids:
the Gram -Are long fatty acids
classification of acid- -Create barrier to hydrophilic molecules
fast
organisms
Cell Wall Composition:
○ Mycolic acids are closely packed in a monolayer
○ Has a low permeability
Explain the ● Impact on Virulence:
composition of the cell ○ Mycolic lipids are "waxy"
wall in acid fast protecting them from antibiotics &
4/35
