MCB3020 EXAM 2 QUESTIONS AND ANSWERS
What is the most common mechanism for bacterial cell division? - Answers - Binary
Fission
List the four steps of the mechanism above. - Answers - 1. Elongation of the cell
2. Replication of the chromosome
3. Separation of the chromosomes into the two parts of the cell
4. Formation of septum in the middle (Cytokinesis, or septation)
Define 'Origin of replication'. - Answers - Where replication begins
How many Origins of replication do bacterial chromosomes have? - Answers - One
What is Cytokinesis? Include a brief overview of its four steps. - Answers - The division
of the cell into two via formation of a cross wall between the two daughter cells.
Define the following terms and their role in cell division:
Penicillin-binding protein (PBP): - Answers - Group of proteins that hydrolyze bonds in
existing peptidoglycan strands and link together new strands.
N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM): - Answers - Major
components of peptidoglycan that bind to a membrane protein called bactoprenol.
Autolysins: - Answers - Degrade polypeptide where new units are to be added, and the
new NAM-NAG units can then be inserted into the peptidoglycan layer.
What is crescentin? - Answers - A homologue of eukaryotic intermediate filaments
What are the other forms of asexual reproduction? Define each - Answers - -Budding:
Budding off daughter cells; seen in Listeria monocytogenes
-Baeocyte formation (multiple fission): Multiple rounds of cell division; seen in
Cyanobacteria
-Spore formation: Form multinucleoid filaments that ultimately divide to produce spores
with a single nucleus.
Know the Bacterial Growth Curve - Answers - lag,log,stationary,dead
List and define each phase of the above curve. - Answers - -Lag Phase: No net growth
because, although the nutrients are abundant, the bacteria are adjusting to new
conditions.
-Log (Exponential) Phase: Nutrients are abundant, and bacteria divide at their highest
rate.
-Stationary Phase: Number of viable microorganisms is stable because the nutrients
level off and waste products accumulate
,-Death Phase: Nutrients are depleted, and levels of waste products and toxins are high,
so the number of viable microorganisms decreases
-Long-term Stationary Phase: Nutrients are depleted, and waves of genetic variants
come and go
True or False: When nutrient levels are low, the limitation of microbial growth occurs as
a result of the saturation of transport proteins for nutrient uptake. - Answers - False;
should be when levels are high
What is generation time (GT)? - Answers - The time it takes the population to double
What phase is it best to calculate GT? - Answers - Log Phase (aka Exponential Phase)
True or False: Cells typically exist in aqueous conditions. - Answers - true
Define hypertonic and hypotonic. - Answers - Hypertonic: One solution has higher
concentration of solutes than another
Hypotonic: One solution has lower concentration of solutes than another
If a cell is in a hypertonic solution it will ____, while in a hypotonic solution it will ____. -
Answers - Shrink; Burst
What are the three distinct cardinal growth temperatures for organisms? - Answers - 1.
Minimum growth temperature: Lowest temperature at which an organism can grow and
survive
2. Maximum growth temperature: Highest temperature at which an organism can grow
and survive
3. Optimal growth temperature: Most suitable temperature for bacterial growth
Know the following microbial adaptations. Define each.
Halophiles - Answers - Grow best in extremely salty environments
b. Xerophiles: - Answers - Grow best in dry conditions
c. Psychrophiles: - Answers - Grow between 0C and 20C - refrigeration temperatures
d. Mesophiles: - Answers - Grow between 20C and 45C
e. Thermophiles: - Answers - Grow between 55C and 85C
f. Hyperthermophiles: - Answers - Grow between 85C and 113C - usually archaens
g. Aerobe: - Answers - Grow in presence of atmospheric oxygen
h. Obligate Aerobes: - Answers - Require oxygen for growth and die without it
, i. Anaerobe: - Answers - Grow in absence of oxygen
j. Obligate Anaerobes: - Answers - Cannot survive in presence of oxygen
k. Facultative Anaerobes: - Answers - Grow better with oxygen than without it (not
needed)
l. Barotolerant: - Answers - Survive increased pressures
True or False: Most human pathogens are Mesophiles. - Answers - TRUE
When does food spoilage occur? - Answers - Occurs when nutritional value, texture, or
flavor of food is changed due to presence of food spoilage organisms.
True or False: Only a select few of our foods contain food spoilage microorganisms. -
Answers - False; All of our foods do
What are the three most common food spoilage organisms? - Answers - Bacteria,
yeasts, and molds
How is food spoilage controlled? - Answers - By manipulating temperature
Define the term sessile. - Answers - Microorganisms that grows attached to a surface
rather than floating freely (planktonic growth).
What do sessile microorganisms form? Define this structure. - Answers - Biofilm: a
complex of slime-enclosed colonies that stick to each other on a surface.
Why does Dr. Bacusmo describe the structure above as an "ecosystem on its own"? -
Answers - Biofilm because a mature biofilm has a heterogenous community of
microorganisms that differ in metabolic activity and physiology.
True or False: Biofilms form only on non-living surfaces, such as medical devices. -
Answers - False: They can also form on living surfaces
What is Quorum Sensing? - Answers - A strategy in which bacteria coordinate the
expression of certain genes based on their population density.
Define and rank these terms from most to least biocidal: Antisepsis, Disinfection,
Sanitization, Sterilization - Answers - 1) Sterilization: refers to the removal or destruction
of all viable microorganisms in the medium
2) Disinfection: involves killing, removing, or inhibiting disease-causing organisms in
medium.
3) Sanitization: involves removing microbial populations to "safe" levels, according to
public health standards.
4) Antisepsis: involves preventing infection of living tissue from microorganisms
What is the most common mechanism for bacterial cell division? - Answers - Binary
Fission
List the four steps of the mechanism above. - Answers - 1. Elongation of the cell
2. Replication of the chromosome
3. Separation of the chromosomes into the two parts of the cell
4. Formation of septum in the middle (Cytokinesis, or septation)
Define 'Origin of replication'. - Answers - Where replication begins
How many Origins of replication do bacterial chromosomes have? - Answers - One
What is Cytokinesis? Include a brief overview of its four steps. - Answers - The division
of the cell into two via formation of a cross wall between the two daughter cells.
Define the following terms and their role in cell division:
Penicillin-binding protein (PBP): - Answers - Group of proteins that hydrolyze bonds in
existing peptidoglycan strands and link together new strands.
N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM): - Answers - Major
components of peptidoglycan that bind to a membrane protein called bactoprenol.
Autolysins: - Answers - Degrade polypeptide where new units are to be added, and the
new NAM-NAG units can then be inserted into the peptidoglycan layer.
What is crescentin? - Answers - A homologue of eukaryotic intermediate filaments
What are the other forms of asexual reproduction? Define each - Answers - -Budding:
Budding off daughter cells; seen in Listeria monocytogenes
-Baeocyte formation (multiple fission): Multiple rounds of cell division; seen in
Cyanobacteria
-Spore formation: Form multinucleoid filaments that ultimately divide to produce spores
with a single nucleus.
Know the Bacterial Growth Curve - Answers - lag,log,stationary,dead
List and define each phase of the above curve. - Answers - -Lag Phase: No net growth
because, although the nutrients are abundant, the bacteria are adjusting to new
conditions.
-Log (Exponential) Phase: Nutrients are abundant, and bacteria divide at their highest
rate.
-Stationary Phase: Number of viable microorganisms is stable because the nutrients
level off and waste products accumulate
,-Death Phase: Nutrients are depleted, and levels of waste products and toxins are high,
so the number of viable microorganisms decreases
-Long-term Stationary Phase: Nutrients are depleted, and waves of genetic variants
come and go
True or False: When nutrient levels are low, the limitation of microbial growth occurs as
a result of the saturation of transport proteins for nutrient uptake. - Answers - False;
should be when levels are high
What is generation time (GT)? - Answers - The time it takes the population to double
What phase is it best to calculate GT? - Answers - Log Phase (aka Exponential Phase)
True or False: Cells typically exist in aqueous conditions. - Answers - true
Define hypertonic and hypotonic. - Answers - Hypertonic: One solution has higher
concentration of solutes than another
Hypotonic: One solution has lower concentration of solutes than another
If a cell is in a hypertonic solution it will ____, while in a hypotonic solution it will ____. -
Answers - Shrink; Burst
What are the three distinct cardinal growth temperatures for organisms? - Answers - 1.
Minimum growth temperature: Lowest temperature at which an organism can grow and
survive
2. Maximum growth temperature: Highest temperature at which an organism can grow
and survive
3. Optimal growth temperature: Most suitable temperature for bacterial growth
Know the following microbial adaptations. Define each.
Halophiles - Answers - Grow best in extremely salty environments
b. Xerophiles: - Answers - Grow best in dry conditions
c. Psychrophiles: - Answers - Grow between 0C and 20C - refrigeration temperatures
d. Mesophiles: - Answers - Grow between 20C and 45C
e. Thermophiles: - Answers - Grow between 55C and 85C
f. Hyperthermophiles: - Answers - Grow between 85C and 113C - usually archaens
g. Aerobe: - Answers - Grow in presence of atmospheric oxygen
h. Obligate Aerobes: - Answers - Require oxygen for growth and die without it
, i. Anaerobe: - Answers - Grow in absence of oxygen
j. Obligate Anaerobes: - Answers - Cannot survive in presence of oxygen
k. Facultative Anaerobes: - Answers - Grow better with oxygen than without it (not
needed)
l. Barotolerant: - Answers - Survive increased pressures
True or False: Most human pathogens are Mesophiles. - Answers - TRUE
When does food spoilage occur? - Answers - Occurs when nutritional value, texture, or
flavor of food is changed due to presence of food spoilage organisms.
True or False: Only a select few of our foods contain food spoilage microorganisms. -
Answers - False; All of our foods do
What are the three most common food spoilage organisms? - Answers - Bacteria,
yeasts, and molds
How is food spoilage controlled? - Answers - By manipulating temperature
Define the term sessile. - Answers - Microorganisms that grows attached to a surface
rather than floating freely (planktonic growth).
What do sessile microorganisms form? Define this structure. - Answers - Biofilm: a
complex of slime-enclosed colonies that stick to each other on a surface.
Why does Dr. Bacusmo describe the structure above as an "ecosystem on its own"? -
Answers - Biofilm because a mature biofilm has a heterogenous community of
microorganisms that differ in metabolic activity and physiology.
True or False: Biofilms form only on non-living surfaces, such as medical devices. -
Answers - False: They can also form on living surfaces
What is Quorum Sensing? - Answers - A strategy in which bacteria coordinate the
expression of certain genes based on their population density.
Define and rank these terms from most to least biocidal: Antisepsis, Disinfection,
Sanitization, Sterilization - Answers - 1) Sterilization: refers to the removal or destruction
of all viable microorganisms in the medium
2) Disinfection: involves killing, removing, or inhibiting disease-causing organisms in
medium.
3) Sanitization: involves removing microbial populations to "safe" levels, according to
public health standards.
4) Antisepsis: involves preventing infection of living tissue from microorganisms
