1|Page
UTA MICROBIOLOGY 2460 EXAM 3 QUESTIONS
| WITH ACTUAL ANSWERS!!
What is FtsZ? - ....ANSWER ....✔✔ protein that directs
cytokinesis and cell division during binary fission
What is culture density? - ....ANSWER ....✔✔ the
number of cells per unit volume
What is the lag phase? - ....ANSWER ....✔✔ inoculum
cells are added and adjust to culture medium
What is the log phase? - ....ANSWER ....✔✔ cells are
dividing by binary fission, cell replication exceeds cell
death, when most susceptible to disinfectants and
antibiotics
What is the stationary phase? - ....ANSWER ....✔✔
waste accumulates and nutrients gradually used up, cell
replication equals cell death
,2|Page
What is the death phase? - ....ANSWER ....✔✔ toxic
waste accumulates and nutrients are exhausted, cell
replication is less than cell death
What are persisters? - ....ANSWER ....✔✔ surviving
cells with slow metabolism, associated with certain
chronic infections like tuberculosis and antibiotic
resistance
What is direct microscopic cell count? - ....ANSWER
....✔✔ cells are manually counted on a Petroff-
Hausser chamber slide under a microscope, cannot
distinguish between living and dead cells, not good with
dilute cultures
What is fluorescence staining? - ....ANSWER ....✔✔
cells are counted under a microscope or flow cytometer
after staining, red stain on dead cells, green on live cells
What is a coulter counter? - ....ANSWER ....✔✔
electronically scans a fluid as it passes through a tiny
pipette, cannot distinguish between living and dead
cells, not good with concentrated cultures
,3|Page
What is a viable plate count? - ....ANSWER ....✔✔
samples are diluted, using serial dilution, and plated via
pour plate or spread plate techniques
counted using CFU/ml
What is the countable range in a plate count? -
....ANSWER ....✔✔ 30-300 CFU/ml
What is the membrane filtration technique? - ....ANSWER
....✔✔ known volume is filtered thru a membrane,
membrane is plated, and colonies are counted
What is Most probable number (MPN)? - ....ANSWER
....✔✔ statistical method used when counts are less
than 30 CFU/ml, 3 log dilutions grown in 3-5 replicates,
growth pattern is compared to reference table
What is optical density? - ....ANSWER ....✔✔
measured turbidity of a sample with a
spectrophotometer, more turbidity equals more growth
What is extracellular polymeric substances (EPS)? -
....ANSWER ....✔✔ substance secreted by organisms
, 4|Page
in the biofilm, hydrated polysaccaride gel with other
macromolecules and channels
What are the steps of formation of a biofilm? -
....ANSWER ....✔✔ 1) reversible attachment of
planktonic cells
2)first colonizers (sessile cells) become irreversibly
attached
3)growth and cell division on substrate
4)production of EPS and formation of water channels
5) attachment of secondary colonizers and dispersion of
microbes to new locations
What type of medium is tryptic soy both/agar
(TSB/TSA)? - ....ANSWER ....✔✔ it is all-purpose
medium
What is enriched medium? - ....ANSWER ....✔✔
contains growth factors, vitamins, and others to promote
growth of fastidious organisms
What is chemically defined medium? - ....ANSWER
....✔✔ exact chemical composition is known
UTA MICROBIOLOGY 2460 EXAM 3 QUESTIONS
| WITH ACTUAL ANSWERS!!
What is FtsZ? - ....ANSWER ....✔✔ protein that directs
cytokinesis and cell division during binary fission
What is culture density? - ....ANSWER ....✔✔ the
number of cells per unit volume
What is the lag phase? - ....ANSWER ....✔✔ inoculum
cells are added and adjust to culture medium
What is the log phase? - ....ANSWER ....✔✔ cells are
dividing by binary fission, cell replication exceeds cell
death, when most susceptible to disinfectants and
antibiotics
What is the stationary phase? - ....ANSWER ....✔✔
waste accumulates and nutrients gradually used up, cell
replication equals cell death
,2|Page
What is the death phase? - ....ANSWER ....✔✔ toxic
waste accumulates and nutrients are exhausted, cell
replication is less than cell death
What are persisters? - ....ANSWER ....✔✔ surviving
cells with slow metabolism, associated with certain
chronic infections like tuberculosis and antibiotic
resistance
What is direct microscopic cell count? - ....ANSWER
....✔✔ cells are manually counted on a Petroff-
Hausser chamber slide under a microscope, cannot
distinguish between living and dead cells, not good with
dilute cultures
What is fluorescence staining? - ....ANSWER ....✔✔
cells are counted under a microscope or flow cytometer
after staining, red stain on dead cells, green on live cells
What is a coulter counter? - ....ANSWER ....✔✔
electronically scans a fluid as it passes through a tiny
pipette, cannot distinguish between living and dead
cells, not good with concentrated cultures
,3|Page
What is a viable plate count? - ....ANSWER ....✔✔
samples are diluted, using serial dilution, and plated via
pour plate or spread plate techniques
counted using CFU/ml
What is the countable range in a plate count? -
....ANSWER ....✔✔ 30-300 CFU/ml
What is the membrane filtration technique? - ....ANSWER
....✔✔ known volume is filtered thru a membrane,
membrane is plated, and colonies are counted
What is Most probable number (MPN)? - ....ANSWER
....✔✔ statistical method used when counts are less
than 30 CFU/ml, 3 log dilutions grown in 3-5 replicates,
growth pattern is compared to reference table
What is optical density? - ....ANSWER ....✔✔
measured turbidity of a sample with a
spectrophotometer, more turbidity equals more growth
What is extracellular polymeric substances (EPS)? -
....ANSWER ....✔✔ substance secreted by organisms
, 4|Page
in the biofilm, hydrated polysaccaride gel with other
macromolecules and channels
What are the steps of formation of a biofilm? -
....ANSWER ....✔✔ 1) reversible attachment of
planktonic cells
2)first colonizers (sessile cells) become irreversibly
attached
3)growth and cell division on substrate
4)production of EPS and formation of water channels
5) attachment of secondary colonizers and dispersion of
microbes to new locations
What type of medium is tryptic soy both/agar
(TSB/TSA)? - ....ANSWER ....✔✔ it is all-purpose
medium
What is enriched medium? - ....ANSWER ....✔✔
contains growth factors, vitamins, and others to promote
growth of fastidious organisms
What is chemically defined medium? - ....ANSWER
....✔✔ exact chemical composition is known
