UTA Microbiology 2460 Exam 3|218
Questions and Answers A+ Rated
What is FtsZ? - -protein that directs cytokinesis and cell division during
binary fission
- What is culture density? - -the number of cells per unit volume
- What is the lag phase? - -inoculum cells are added and adjust to culture
medium
- What is the log phase? - -cells are dividing by binary fission, cell replication
exceeds cell death, when most susceptible to disinfectants and antibiotics
- What is the stationary phase? - -waste accumulates and nutrients gradually
used up, cell replication equals cell death
- What is the death phase? - -toxic waste accumulates and nutrients are
exhausted, cell replication is less than cell death
- What are persisters? - -surviving cells with slow metabolism, associated
with certain chronic infections like tuberculosis and antibiotic resistance
- What is direct microscopic cell count? - -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? - -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? - -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? - -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? - -30-300 CFU/ml
- What is the membrane filtration technique? - -known volume is filtered thru
a membrane, membrane is plated, and colonies are counted
, - What is Most probable number (MPN)? - -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? - -measured turbidity of a sample with a
spectrophotometer, more turbidity equals more growth
- What is extracellular polymeric substances (EPS)? - -substance secreted by
organisms in the biofilm, hydrated polysaccaride gel with other
macromolecules and channels
- What are the steps of formation of a biofilm? - -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)? - -it is all-purpose
medium
- What is enriched medium? - -contains growth factors, vitamins, and others
to promote growth of fastidious organisms
- What is chemically defined medium? - -exact chemical composition is
known
- What is complex medium? - -contains extracts and digests of yeasts, meat,
or plants
the composition is unknown
- What is selective medium? - -inhibits unwanted growth and promotes
growth of the interested organism
- What is an enrichment culture? - -promotes growth of desired microbe
when many different organisms are present
- What is differential medium? - -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? - -total plate count
- In which phase would you expect to observe the most endospores in a
Bacillus cell culture? - -death phase
, - During which phase would penicillin be most effective? - -log phase
- What is the best definition of generation time in a bacterium? - -the length
of time it takes for a population of cells to double
- What is the function of the Z ring in binary fission? - -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? - -1,600
- Filamentous cyanobacteria often divide by which of the following? - -
fragmentation
- Which is a reason for antimicrobial resistance being higher in a biofilm than
in free-floating bacterial cells? - -Cells are metabolically inactive at the base
of a biofilm
- Quorum sensing is used by bacterial cells to determine ___? - -the density
of the population
- Which of the following statements about autoinducers is incorrect?
a. they bind directly to DNA to activate transcription
b. they can activate the cell that secreted them
c. N-acylated homoserine lactones are autoinducers in gram-negative cells
d. autoinducers may stimulate the production of virulence factors - -a. they
bind directly to DNA to activate transcription
- An inoculated thioglycolate medium culture tube shows dense growth at
the surface and growth throughout the rest of the tube. What is your
conclusion? - -the organisms are faculatative anaerobes
- An inoculated thioglycolate medium culture tube is clear throughout the
tube except for dense growth at the bottom of the tube. What is your
conclusion? - -the organisms are obligate anaerobes
- Pseudomonas aeruginosa is a common pathogen that infects the airways
of patients with cystic fibrosis. It does not grow in the absence of oxygen.
The bacterium is probably ___? - -an obligate aerobe
- Streptococcus mutans is a major cause of cavities. It resides in the gum
pockets, does not have catalase activity, and can be grown outside of an
anaerobic chamber. The bacterium is probably ___? - -an aerotolerant
anaerobe
Questions and Answers A+ Rated
What is FtsZ? - -protein that directs cytokinesis and cell division during
binary fission
- What is culture density? - -the number of cells per unit volume
- What is the lag phase? - -inoculum cells are added and adjust to culture
medium
- What is the log phase? - -cells are dividing by binary fission, cell replication
exceeds cell death, when most susceptible to disinfectants and antibiotics
- What is the stationary phase? - -waste accumulates and nutrients gradually
used up, cell replication equals cell death
- What is the death phase? - -toxic waste accumulates and nutrients are
exhausted, cell replication is less than cell death
- What are persisters? - -surviving cells with slow metabolism, associated
with certain chronic infections like tuberculosis and antibiotic resistance
- What is direct microscopic cell count? - -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? - -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? - -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? - -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? - -30-300 CFU/ml
- What is the membrane filtration technique? - -known volume is filtered thru
a membrane, membrane is plated, and colonies are counted
, - What is Most probable number (MPN)? - -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? - -measured turbidity of a sample with a
spectrophotometer, more turbidity equals more growth
- What is extracellular polymeric substances (EPS)? - -substance secreted by
organisms in the biofilm, hydrated polysaccaride gel with other
macromolecules and channels
- What are the steps of formation of a biofilm? - -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)? - -it is all-purpose
medium
- What is enriched medium? - -contains growth factors, vitamins, and others
to promote growth of fastidious organisms
- What is chemically defined medium? - -exact chemical composition is
known
- What is complex medium? - -contains extracts and digests of yeasts, meat,
or plants
the composition is unknown
- What is selective medium? - -inhibits unwanted growth and promotes
growth of the interested organism
- What is an enrichment culture? - -promotes growth of desired microbe
when many different organisms are present
- What is differential medium? - -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? - -total plate count
- In which phase would you expect to observe the most endospores in a
Bacillus cell culture? - -death phase
, - During which phase would penicillin be most effective? - -log phase
- What is the best definition of generation time in a bacterium? - -the length
of time it takes for a population of cells to double
- What is the function of the Z ring in binary fission? - -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? - -1,600
- Filamentous cyanobacteria often divide by which of the following? - -
fragmentation
- Which is a reason for antimicrobial resistance being higher in a biofilm than
in free-floating bacterial cells? - -Cells are metabolically inactive at the base
of a biofilm
- Quorum sensing is used by bacterial cells to determine ___? - -the density
of the population
- Which of the following statements about autoinducers is incorrect?
a. they bind directly to DNA to activate transcription
b. they can activate the cell that secreted them
c. N-acylated homoserine lactones are autoinducers in gram-negative cells
d. autoinducers may stimulate the production of virulence factors - -a. they
bind directly to DNA to activate transcription
- An inoculated thioglycolate medium culture tube shows dense growth at
the surface and growth throughout the rest of the tube. What is your
conclusion? - -the organisms are faculatative anaerobes
- An inoculated thioglycolate medium culture tube is clear throughout the
tube except for dense growth at the bottom of the tube. What is your
conclusion? - -the organisms are obligate anaerobes
- Pseudomonas aeruginosa is a common pathogen that infects the airways
of patients with cystic fibrosis. It does not grow in the absence of oxygen.
The bacterium is probably ___? - -an obligate aerobe
- Streptococcus mutans is a major cause of cavities. It resides in the gum
pockets, does not have catalase activity, and can be grown outside of an
anaerobic chamber. The bacterium is probably ___? - -an aerotolerant
anaerobe
