MICROBIOLOGY UTA 2460 EXAM 3 ACTUAL
SCRIPT 2026 COMPLETE QUESTIONS AND
CORRECT ANSWERS GRADED A+
◉ 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 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 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 type of medium is tryptic soy both/agar (TSB/TSA)?
Answer: it is all-purpose medium
◉ 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
◉ If a culture starts with 50 cells, how many cells will be present
after five generations with no cell death?
Answer: 1,600
◉ Which environment would harbor psychrophiles?
Answer: mountain lake with a water temperature of 12 degrees C
, ◉ What is the reason jams and dried meats often do not require
refrigeration to prevent spoilage?
Answer: low water activity
◉ Bacteria living in salt marshes are most likely ___?
Answer: halotolerant
◉ EMB agar is a medium used in the identification and isolation of
pathogenic bacteria. It contains digested meat proteins as a source
of organic nutrients. Two indicator dyes, eosin and methylene blue,
inhibit the growth of gram-positive bacteria and distinguish
between lactose fermenting and nonlactose fermenting organisms.
Lactose fermenters form metallic green or deep purple colonies,
whereas the nonlactose fermenters form completely colorless
colonies. EMB agar is an example of ___?
Answer: a selective medium, a differential medium, and a complex
medium
◉ Haemophilus influenzae must be grown on chocolate agar, which
is blood agar treated with heat to release growth factors in the
medium. H. influenzae is described as ___.
Answer: fastidious
◉ Direct count of total cells can be performed using a ________ or a
________.
SCRIPT 2026 COMPLETE QUESTIONS AND
CORRECT ANSWERS GRADED A+
◉ 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 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 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 type of medium is tryptic soy both/agar (TSB/TSA)?
Answer: it is all-purpose medium
◉ 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
◉ If a culture starts with 50 cells, how many cells will be present
after five generations with no cell death?
Answer: 1,600
◉ Which environment would harbor psychrophiles?
Answer: mountain lake with a water temperature of 12 degrees C
, ◉ What is the reason jams and dried meats often do not require
refrigeration to prevent spoilage?
Answer: low water activity
◉ Bacteria living in salt marshes are most likely ___?
Answer: halotolerant
◉ EMB agar is a medium used in the identification and isolation of
pathogenic bacteria. It contains digested meat proteins as a source
of organic nutrients. Two indicator dyes, eosin and methylene blue,
inhibit the growth of gram-positive bacteria and distinguish
between lactose fermenting and nonlactose fermenting organisms.
Lactose fermenters form metallic green or deep purple colonies,
whereas the nonlactose fermenters form completely colorless
colonies. EMB agar is an example of ___?
Answer: a selective medium, a differential medium, and a complex
medium
◉ Haemophilus influenzae must be grown on chocolate agar, which
is blood agar treated with heat to release growth factors in the
medium. H. influenzae is described as ___.
Answer: fastidious
◉ Direct count of total cells can be performed using a ________ or a
________.
