Microbiology

Question 1

Give the gram stain and structure of Neisseria meningitidis

Answer 1

gram -ve diplococcus

Question 2

Give the gram stain and structure of streptococcus mutans

Answer 2

gram +ve streptococcus

Question 3

Give the gram stain and structure of streptococcus pneumoniae

Answer 3

gram +ve diplococcus

Question 4

Give the gram stain and structure of haemophilus influenzae

Answer 4

gram -ve coccobacillus

Question 5

Give the gram stain and structure of vibrio cholerae

Answer 5

gram -ve vibrio

Question 6

Give the gram stain and structure of salmonella typhi

Answer 6

gram -ve rod

Question 7

Give the gram stain and structure of corynebacterium diptheriae?

Answer 7

gram +ve rod

Question 8

Give the gram stain and structure of clostridium difficile

Answer 8

gram +ve rod

Question 9

Categorise s. aureus and s. pyogenes as catalase positive or negative. What does this test mean?

Answer 9

S. aureus = catalase +ve
S. pyogenes (+ all other streps) = catalase -ve

Catalase converts hydrogen peroxide to water and o2.

Question 10

Which dye is responsible for the colouration of gram +ve bacteria?

Answer 10

Crystal violet - purple

Question 11

Which dye is responsible for the colouration of gram -ve bacteria?

Answer 11

Safranin

Question 12

What is the purpose of passing the microscope slide through a Bunsen burner?

Answer 12

This is to fix the bacteria firmly to the slide.

It also kills the bacteria, making it safe to handle, without destroying internal structures.

Question 13

What are inclusion bodies and where are they found?

Answer 13

They are stores of carbon, fats and phosphates.

They are found in the cytoplasm.

Question 14

Which environment is most likely to result in a bacteria making a pilus:
low shear force or high shear force

Answer 14

High shear force as the bacteria may want to adhere to the surface so it doesn’t move away from its optimum site.

Question 15

Why don’t bacteria express pili all the time?

Answer 15

Because it requires a lot of energy and nutrients to make and it reduces the surface area available for metabolic processes.

Question 16

What type of bacteria are found on the skin mainly?

Answer 16

Gram +ve bacteria

Although behind neck, on hands etc don’t get much air so they are mainly gram -ve

Question 17

Which protein systems move
a) folded
b) unfolded
proteins across the inner membrane?

Answer 17

folded = sec 
unfolded = TAT (twin-arginine translocation pathway)

Question 18

What are slime layers and capsules made of?

What is the difference between the two?

Answer 18

They are made of polysaccharides

Capsules are highly organised and are hard to remove.
Slime layers are disorganised and easy to remove.

Question 19

Name some encapsulated bacteria and an encapsulated fungus.

Answer 19

Way to remember =
SHiN Kills Some Patients with Capsules

Streptococcus pneumoniae
Haemophilus influenzae
Neisseria meningitidis
Klebsiella pneumoniae
Salmonella typhi
Pseudomonas aeruginosa
Cryptococcus neoformans - only encapsulated fungus

Question 20

Define these words?
Monotrichous

Amphitrichous

Peritrichous

Answer 20

Monotrichous = one flagellum

Amphitrichous = one flagellum at each end

Peritrichous = spread over entire cell surface

Question 21

What is the word to describe an organism with clusters of flagella at one or both ends?

Answer 21

Iophotrichous

Question 22

Give an example of a bacteria with iophotrichous flagella?

Answer 22

Legionella pneumophilia

Question 23

What sort of flagella does salmonella have?

Answer 23

peritrichous

Question 24

What type of bacteria usually form endospores?

Answer 24

Gram +ve rods

Question 25

What are AB toxins?

Answer 25

Some exotoxins are AB toxins…

A - has derogatory function on the cell
B - facilitates the uptake of A

Question 26

What is the indole test testing?

Answer 26

It is testing for the presence of tryptophanase which converts tryptophan into indole.

Question 27

Give an example of indole test positive bacteria?

Answer 27

E. coli

Question 28

What is the carbohydrate utilisation test and what is it testing?

Answer 28

Different carbohydrates are placed into the container with bacteria.
It is testing whether or not the bacteria can ferment the carbohydrates, producing a byproduct of acid.
This acid will turn the phenol indicator yellow.

Question 29

What is alpha, beta and gamma haemolysis?

Answer 29

Alpha = partial haemolysis, turns green
Beta = full haemolysis
Gamma = no haemolysis