MICROBIOLOGY UTA 2460 EXAM 3 EXAMPREP
2026 COMPLETE QUESTIONS AND ANSWERS
ALREADY PASSED
◉ 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
◉ 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
◉ 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 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
◉ What is complex medium?
Answer: contains extracts and digests of yeasts, meat, or plants
the composition is unknown
◉ What is selective medium?
Answer: inhibits unwanted growth and promotes growth of the
interested organism
2026 COMPLETE QUESTIONS AND ANSWERS
ALREADY PASSED
◉ 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
◉ 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
◉ 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 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
◉ What is complex medium?
Answer: contains extracts and digests of yeasts, meat, or plants
the composition is unknown
◉ What is selective medium?
Answer: inhibits unwanted growth and promotes growth of the
interested organism
