MICR 3060 FINAL EXAM QUESTIONS WITH VERIFIED
ANSWERS
What type of UV light is the most germicidal? - Answers - UV-C (~260 nm)
How does UV light kill bacteria? - Answers - forms thymine dimers in DNA which block
replication
Why is UV light only effective on surfaces? - Answers - it has low penetration power
Which organism was more resistant to UV: S. Aureus or B. Subtilis? Why? - Answers -
B. Subtilis because it forms endospores
How did we test UV effectiveness in lab? - Answers - exposed half a plate (with/without
cover) for varying times and compared bacterial growth
What is ammonification? - Answers - conversion of organic nitrogen into ammonia
(NH4+)
How did we test for ammonification in the lab? - Answers - used nessler's reagent on
peptone broth that contained a loopful of soil
What does a brown color with nessler's reagent indicate? - Answers - high ammonia
production
What does a light yellow color with nessler's reagent indicate? - Answers - small amount
of ammonia is present
What does a deep yellow color with nessler's reagent indicate? - Answers - moderate
amounts of ammonia are present
What is a biofilm? - Answers - a community of microbes attached to a surface in a
protective matrix
What is quorum sensing? - Answers - cell-to-cell communication that regulates group
behavior
Why are biofilms dangerous? - Answers - they are resistant to antibiotics and
disinfectants
Where are biofilms commonly found? - Answers - medical devices like catheters
What is an antimicrobial agent? - Answers - any substance that kills or inhibits microbes
, What is a disinfectant? - Answers - used on non-living surfaces
What is an antiseptic? - Answers - used on living tissue
What is an antibiotic? - Answers - a drug that specifically targets bacteria
What is the purpose of the filter paper disk method? - Answers - to test effectiveness of
disinfectants
What does a larger zone of inhibition indicate? - Answers - more effective antibiotic
What is the kirby-bauer method used for? - Answers - testing bacterial sensitivity to
antibiotics
What is a zone of inhibition? - Answers - clear area where bacteria did not grow
What does a smaller zone of inhibition indicate? - Answers - bacteria are resistant
What type of growth must be present before adding disks? - Answers - uniform bacterial
lawn
What was the purpose of the hand cleaning experiment? - Answers - To compare
effectiveness of cleaning methods
How was effectiveness measured? - Answers - Colony counts and percent reduction
What is the purpose of the methylene blue reductase test? - Answers - To assess milk
quality
Why does methylene blue lose color? - Answers - Bacteria consume oxygen
What does fast decolorization indicate? - Answers - Poor-quality milk
What does slow decolorization indicate? - Answers - High-quality milk
What does MBRT stand for? - Answers - Methylene Blue Reduction Time
What is the purpose of a standard plate count? - Answers - To determine number of
bacteria in a sample
What is CFU? - Answers - Colony forming unit
What is the formula for CFU/ml? - Answers - colonies × reciprocal of dilution
What is a countable plate? - Answers - 30-300 colonies
ANSWERS
What type of UV light is the most germicidal? - Answers - UV-C (~260 nm)
How does UV light kill bacteria? - Answers - forms thymine dimers in DNA which block
replication
Why is UV light only effective on surfaces? - Answers - it has low penetration power
Which organism was more resistant to UV: S. Aureus or B. Subtilis? Why? - Answers -
B. Subtilis because it forms endospores
How did we test UV effectiveness in lab? - Answers - exposed half a plate (with/without
cover) for varying times and compared bacterial growth
What is ammonification? - Answers - conversion of organic nitrogen into ammonia
(NH4+)
How did we test for ammonification in the lab? - Answers - used nessler's reagent on
peptone broth that contained a loopful of soil
What does a brown color with nessler's reagent indicate? - Answers - high ammonia
production
What does a light yellow color with nessler's reagent indicate? - Answers - small amount
of ammonia is present
What does a deep yellow color with nessler's reagent indicate? - Answers - moderate
amounts of ammonia are present
What is a biofilm? - Answers - a community of microbes attached to a surface in a
protective matrix
What is quorum sensing? - Answers - cell-to-cell communication that regulates group
behavior
Why are biofilms dangerous? - Answers - they are resistant to antibiotics and
disinfectants
Where are biofilms commonly found? - Answers - medical devices like catheters
What is an antimicrobial agent? - Answers - any substance that kills or inhibits microbes
, What is a disinfectant? - Answers - used on non-living surfaces
What is an antiseptic? - Answers - used on living tissue
What is an antibiotic? - Answers - a drug that specifically targets bacteria
What is the purpose of the filter paper disk method? - Answers - to test effectiveness of
disinfectants
What does a larger zone of inhibition indicate? - Answers - more effective antibiotic
What is the kirby-bauer method used for? - Answers - testing bacterial sensitivity to
antibiotics
What is a zone of inhibition? - Answers - clear area where bacteria did not grow
What does a smaller zone of inhibition indicate? - Answers - bacteria are resistant
What type of growth must be present before adding disks? - Answers - uniform bacterial
lawn
What was the purpose of the hand cleaning experiment? - Answers - To compare
effectiveness of cleaning methods
How was effectiveness measured? - Answers - Colony counts and percent reduction
What is the purpose of the methylene blue reductase test? - Answers - To assess milk
quality
Why does methylene blue lose color? - Answers - Bacteria consume oxygen
What does fast decolorization indicate? - Answers - Poor-quality milk
What does slow decolorization indicate? - Answers - High-quality milk
What does MBRT stand for? - Answers - Methylene Blue Reduction Time
What is the purpose of a standard plate count? - Answers - To determine number of
bacteria in a sample
What is CFU? - Answers - Colony forming unit
What is the formula for CFU/ml? - Answers - colonies × reciprocal of dilution
What is a countable plate? - Answers - 30-300 colonies
