MICROBIOLOGY UTA 2460 EXAM 3 STUDY
GUIDE 2026 TESTED QUESTIONS AND
PRACTICE SOLUTION GRADED A+
◉ 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
◉ What is an enrichment culture?
Answer: promotes growth of desired microbe when many different
organisms are present
◉ What is differential medium?
Answer: distinguishes between different groups of bacteria by a
change in color
◉ What method would be used to measure the concentration of
bacterial contamination in processed peanut butter?
Answer: total plate count
, ◉ In which phase would you expect to observe the most endospores
in a Bacillus cell culture?
Answer: death phase
◉ During which phase would penicillin be most effective?
Answer: log phase
◉ What is the best definition of generation time in a bacterium?
Answer: the length of time it takes for a population of cells to double
◉ What is the function of the Z ring in binary fission?
Answer: it forms a contractile ring at the septum
◉ If a culture starts with 50 cells, how many cells will be present
after five generations with no cell death?
Answer: 1,600
◉ Filamentous cyanobacteria often divide by which of the following?
Answer: fragmentation
◉ Which is a reason for antimicrobial resistance being higher in a
biofilm than in free-floating bacterial cells?
GUIDE 2026 TESTED QUESTIONS AND
PRACTICE SOLUTION GRADED A+
◉ 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
◉ What is an enrichment culture?
Answer: promotes growth of desired microbe when many different
organisms are present
◉ What is differential medium?
Answer: distinguishes between different groups of bacteria by a
change in color
◉ What method would be used to measure the concentration of
bacterial contamination in processed peanut butter?
Answer: total plate count
, ◉ In which phase would you expect to observe the most endospores
in a Bacillus cell culture?
Answer: death phase
◉ During which phase would penicillin be most effective?
Answer: log phase
◉ What is the best definition of generation time in a bacterium?
Answer: the length of time it takes for a population of cells to double
◉ What is the function of the Z ring in binary fission?
Answer: it forms a contractile ring at the septum
◉ If a culture starts with 50 cells, how many cells will be present
after five generations with no cell death?
Answer: 1,600
◉ Filamentous cyanobacteria often divide by which of the following?
Answer: fragmentation
◉ Which is a reason for antimicrobial resistance being higher in a
biofilm than in free-floating bacterial cells?
