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UTA Microbiology Tholen: Exam 4
Binary Fission - ....ANSWER ....✔✔ The MOST
COMMON mechanism of cell replication
Binary Fission Steps: - ....ANSWER ....✔✔ 1) Growth
of cell size and increase in cell components
2) Replication of DNA
3) Division of the cytoplasm (cytokinesis)
4) Septum formation and division of daughter cells
Z-ring Assembly - ....ANSWER ....✔✔ 1) Cytokinesis is
directed by Ftsz protein
2) Ftsz assembles z-ring to form divisome
3) Divisome activates production of peptidoglycan and
septum
Generation Time - ....ANSWER ....✔✔ aka Doubling
Time; the time it takes for the pop. to double thru one
round of binary fission
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Bacterium Generation Times - ....ANSWER ....✔✔ E.
coli: 20 mins
B. subtilis: 120 mins
S. aureus: 30 mins
M. tuberculosis: 15-20 hrs
Formula for Generation Time - ....ANSWER ....✔✔
Nn= N02^n; n= # of generations, N0= initial # of cells
Growth Curve - ....ANSWER ....✔✔ closed cultures
have finite resources
open system cultures have infinite resources
Nutrients and air are replenished, dead cells and waste
are removed = BENEFICIAL FOR INDUSTRIAL
MICROBIOLOGY
Growth Curve Phases - ....ANSWER ....✔✔ 1) Lag
phase: cells adjust to culture medium, no change in
pop.
2) Log (exponential) phase: binary fission occurs; cell
replication > cell death
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3) Stationary phase: resources are depleted; cell
replication = cell death
4) Death phase: endospores can form; cell replication <
cell death
Measuring Growth - ....ANSWER ....✔✔ Quantifying
pop. size is important to determine infection,
contamination of water or food supply, etc.
Measuring Growth Methods: Microscopic cell count -
....ANSWER ....✔✔ cells are counted under a
microscope; known volume is transferred to a
calibrated slide and cells are manually counted; cannot
distinguish live vs. dead
Measuring Growth Methods: Fluorescence staining -
....ANSWER ....✔✔ cells are counted under a
microscope/ flow cytometer; Red stains binds to
damaged cells to indicate dead cells
Measuring Growth Methods: Viable cell counts -
....ANSWER ....✔✔ samples are diluted and grown as
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solid media; results expressed in colony forming units
per volume (CFU/mL)
Viable cell counts are limited to - ....ANSWER ....✔✔
easily cultured species
Serial dilution is plated and counted by - ....ANSWER
....✔✔ pour plate or spread plate technique
Dilutions are often on - ....ANSWER ....✔✔ log scale
Dilution factor is used to determine - ....ANSWER
....✔✔ original CFU count
Most Probable Number (MPN) - ....ANSWER ....✔✔
statistical method used when counts are VERY low (<30
CFU/mL); used in food and water testing
Growth can be determined as either - ....ANSWER
....✔✔ positive or negative; Pattern= 5,2,0
UTA Microbiology Tholen: Exam 4
Binary Fission - ....ANSWER ....✔✔ The MOST
COMMON mechanism of cell replication
Binary Fission Steps: - ....ANSWER ....✔✔ 1) Growth
of cell size and increase in cell components
2) Replication of DNA
3) Division of the cytoplasm (cytokinesis)
4) Septum formation and division of daughter cells
Z-ring Assembly - ....ANSWER ....✔✔ 1) Cytokinesis is
directed by Ftsz protein
2) Ftsz assembles z-ring to form divisome
3) Divisome activates production of peptidoglycan and
septum
Generation Time - ....ANSWER ....✔✔ aka Doubling
Time; the time it takes for the pop. to double thru one
round of binary fission
,2|Page
Bacterium Generation Times - ....ANSWER ....✔✔ E.
coli: 20 mins
B. subtilis: 120 mins
S. aureus: 30 mins
M. tuberculosis: 15-20 hrs
Formula for Generation Time - ....ANSWER ....✔✔
Nn= N02^n; n= # of generations, N0= initial # of cells
Growth Curve - ....ANSWER ....✔✔ closed cultures
have finite resources
open system cultures have infinite resources
Nutrients and air are replenished, dead cells and waste
are removed = BENEFICIAL FOR INDUSTRIAL
MICROBIOLOGY
Growth Curve Phases - ....ANSWER ....✔✔ 1) Lag
phase: cells adjust to culture medium, no change in
pop.
2) Log (exponential) phase: binary fission occurs; cell
replication > cell death
,3|Page
3) Stationary phase: resources are depleted; cell
replication = cell death
4) Death phase: endospores can form; cell replication <
cell death
Measuring Growth - ....ANSWER ....✔✔ Quantifying
pop. size is important to determine infection,
contamination of water or food supply, etc.
Measuring Growth Methods: Microscopic cell count -
....ANSWER ....✔✔ cells are counted under a
microscope; known volume is transferred to a
calibrated slide and cells are manually counted; cannot
distinguish live vs. dead
Measuring Growth Methods: Fluorescence staining -
....ANSWER ....✔✔ cells are counted under a
microscope/ flow cytometer; Red stains binds to
damaged cells to indicate dead cells
Measuring Growth Methods: Viable cell counts -
....ANSWER ....✔✔ samples are diluted and grown as
, 4|Page
solid media; results expressed in colony forming units
per volume (CFU/mL)
Viable cell counts are limited to - ....ANSWER ....✔✔
easily cultured species
Serial dilution is plated and counted by - ....ANSWER
....✔✔ pour plate or spread plate technique
Dilutions are often on - ....ANSWER ....✔✔ log scale
Dilution factor is used to determine - ....ANSWER
....✔✔ original CFU count
Most Probable Number (MPN) - ....ANSWER ....✔✔
statistical method used when counts are VERY low (<30
CFU/mL); used in food and water testing
Growth can be determined as either - ....ANSWER
....✔✔ positive or negative; Pattern= 5,2,0
