BIOL 351 EXAM 2 2026-2027 QUESTIONS AND
CORRECT ANSWERS GRADED A+
What is the standard tool for measuring the effectiveness of antimicrobials against
pathogenic microorganisms?
Kirby-Bauer test or disk diffusion test
The size of the "zone of inhibition" depends upon
Sensitivity of the bacteria to the specific microbial agent
If a clear zone appears around the disk, is the organism susceptible or resistant to
the antimicrobial?
Susceptible
Brilliant Green Lactose Bile Broth (BGLB) is what type of medium?
Selective and differential
How does Brilliant Green Lactose Bile (BGLB) have selective media
characteristics?
The broth contains bile and brilliant green dye which inhibit the growth of gram
(+) organisms
,How does Brilliant Green Lactose Bile (BGLB) have differential media
characteristics?
The broth contains lactose as the main source for fermentation, only organisms that
can ferment lactose will grow
What indicates a positive result after inoculation of Brilliant Green Lactose Bile
(BGLB)?
Turbidity (cloudiness) in the broth and gas bubbles in the Durham tubes
What is the formula to calculate the original cell density (CFU/mL)?
# of colonies / (volume plated * dilution)
What is the largest majority of microbes found in the soil?
Saprophytes
What microorganism can break down organic matter to enrich the soil?
Saprophytes
Which two microbes are responsible for about 2/3rds of the antibiotics used today?
Actinobacteria and fungi
, What type of media is Tryptic Soy Agar (TSA)?
Non-selective
Where do fecal coliforms live?
The digestive tract of animals
What are the 4 bacteria that make up the total number of coliforms?
Enterobacter, Klebsiella, Citrobacter, or Escherichia
How can the number of total coliforms in a water sample be determined by
statistical estimation?
Most probable number (MPN) test
Why are the number of total coliforms tested by multiple series of Durham
fermentation tubes and not a plate count method?
Non-coliform microorganisms in the sample would interfere if a plate count
method was used
What is the presumptive test?
CORRECT ANSWERS GRADED A+
What is the standard tool for measuring the effectiveness of antimicrobials against
pathogenic microorganisms?
Kirby-Bauer test or disk diffusion test
The size of the "zone of inhibition" depends upon
Sensitivity of the bacteria to the specific microbial agent
If a clear zone appears around the disk, is the organism susceptible or resistant to
the antimicrobial?
Susceptible
Brilliant Green Lactose Bile Broth (BGLB) is what type of medium?
Selective and differential
How does Brilliant Green Lactose Bile (BGLB) have selective media
characteristics?
The broth contains bile and brilliant green dye which inhibit the growth of gram
(+) organisms
,How does Brilliant Green Lactose Bile (BGLB) have differential media
characteristics?
The broth contains lactose as the main source for fermentation, only organisms that
can ferment lactose will grow
What indicates a positive result after inoculation of Brilliant Green Lactose Bile
(BGLB)?
Turbidity (cloudiness) in the broth and gas bubbles in the Durham tubes
What is the formula to calculate the original cell density (CFU/mL)?
# of colonies / (volume plated * dilution)
What is the largest majority of microbes found in the soil?
Saprophytes
What microorganism can break down organic matter to enrich the soil?
Saprophytes
Which two microbes are responsible for about 2/3rds of the antibiotics used today?
Actinobacteria and fungi
, What type of media is Tryptic Soy Agar (TSA)?
Non-selective
Where do fecal coliforms live?
The digestive tract of animals
What are the 4 bacteria that make up the total number of coliforms?
Enterobacter, Klebsiella, Citrobacter, or Escherichia
How can the number of total coliforms in a water sample be determined by
statistical estimation?
Most probable number (MPN) test
Why are the number of total coliforms tested by multiple series of Durham
fermentation tubes and not a plate count method?
Non-coliform microorganisms in the sample would interfere if a plate count
method was used
What is the presumptive test?
