UMHB MICROBIOLOGY LAB FINAL
EXAM QUESTIONS AND ANSWERS
GRADED A+ 2025/2026
The two terms describe the movement of bacteria based on the rotation direction of their
flagella ______
and _______. - ANS Running and tumbling
You are looking at pond water with a 40x objective lens and see roundish green things. You
conclude they are what? - ANS Algae
Give at least two reasons why microbes are often hard to see in wet preparations(living
samples) - ANS - Motile bacteria move very quickly
- They are not stained which makes them hard to see
Name four different structures that cells can use for motility - ANS -flagella
- fimbriae
- pili
- axial filaments
1 @COPYRIGHT 2026 ALLRIGHTS RESERVED.
, How can flagella enhance a bacterium's virulence? - ANS Flagella allows them to move away
from phagocyte's and harmful chemicals, and flagella allow them to move around and spread
quickly
amphitrichous flagella - ANS flagella at both ends(ambidextrous)
What is a pure culture of bacteria? - ANS a culture consisting of only 1 bacterial species
Why mixed cultures are of little use in studying microorganisms? - ANS Because they are so
close together it is hard to identify specific structures
Why would pour plate technique be used instead of the streak plate method to obtain colonies?
- ANS Because the colony growth is restricted by being embedded into the agar
Why is MacConkey agar considered both a selective and a differential medium? - ANS - It is
selective because gram + does not grow, while it promotes gram - bacteria
- It is differential because it has a difference in reaction depending on what the color changes.
Between the lactose fermenter and the non-lactose fermenter
What two components make MacConkey's agar a differential medium? - ANS Neutral Red
and Lactose
What two components make MacConkey's agar a selective medium? - ANS Bile salts and
crystal violet
What is tge purpose of NaCL in MacConkey's agar - ANS maintain osmotic pressure
2 @COPYRIGHT 2026 ALLRIGHTS RESERVED.
EXAM QUESTIONS AND ANSWERS
GRADED A+ 2025/2026
The two terms describe the movement of bacteria based on the rotation direction of their
flagella ______
and _______. - ANS Running and tumbling
You are looking at pond water with a 40x objective lens and see roundish green things. You
conclude they are what? - ANS Algae
Give at least two reasons why microbes are often hard to see in wet preparations(living
samples) - ANS - Motile bacteria move very quickly
- They are not stained which makes them hard to see
Name four different structures that cells can use for motility - ANS -flagella
- fimbriae
- pili
- axial filaments
1 @COPYRIGHT 2026 ALLRIGHTS RESERVED.
, How can flagella enhance a bacterium's virulence? - ANS Flagella allows them to move away
from phagocyte's and harmful chemicals, and flagella allow them to move around and spread
quickly
amphitrichous flagella - ANS flagella at both ends(ambidextrous)
What is a pure culture of bacteria? - ANS a culture consisting of only 1 bacterial species
Why mixed cultures are of little use in studying microorganisms? - ANS Because they are so
close together it is hard to identify specific structures
Why would pour plate technique be used instead of the streak plate method to obtain colonies?
- ANS Because the colony growth is restricted by being embedded into the agar
Why is MacConkey agar considered both a selective and a differential medium? - ANS - It is
selective because gram + does not grow, while it promotes gram - bacteria
- It is differential because it has a difference in reaction depending on what the color changes.
Between the lactose fermenter and the non-lactose fermenter
What two components make MacConkey's agar a differential medium? - ANS Neutral Red
and Lactose
What two components make MacConkey's agar a selective medium? - ANS Bile salts and
crystal violet
What is tge purpose of NaCL in MacConkey's agar - ANS maintain osmotic pressure
2 @COPYRIGHT 2026 ALLRIGHTS RESERVED.
