CMB1003/L02 Bacterial Shape, Size etc

Question 1

Describe the process of Gram staining. (4)

Answer 1

Primary stain - crystal violet
Iodine - mordant
Wash with alcohol decolouriser
Safranin counterstain

Question 2

What colour do Gram negative and positive bacteria stain?

Answer 2

Gram positive - purple
Gram negative - pink

Question 3

What is the difference between Gram positive and negative bacteria?

Answer 3

+ve - outer many layers of peptidoglycan
-ve - inner and outer membrane with peptidoglycan between

Question 4

Why are bacterial cell walls important? (3)

Answer 4

Protection against osmotic and environmental stresses
Defines shape
Helps with uniform cell division

Question 5

What is the bacterial cell wall a target for?

Answer 5

Immune defenses
Antibiotics

Question 6

What is Green Fluorescent Protein (GFP)?

Answer 6

Genetic manipulation to make protein-GFP fusion

Question 7

What does Green Fluorescent Protein enable?

Answer 7

Live cell, time lapse imaging

Question 8

Give 2 disadvantages to Green Fluorescent Protein.

Answer 8

Many fusion proteins malfunction
Localisation may be misleading

Question 9

What is the FtZ ring in bacteria equivalent to in eukaryotes?

Answer 9

Eukaryotic tubulin

Question 10

What is MreB equivalent to in eukaryotes?

Answer 10

Eukaryotic actin

Question 11

Which cells have a proteinaceous S-layer?

Answer 11

Many bacteria
Most archaea

Question 12

What is a proteinaceous S-layer?

Answer 12

Outermost layer of cell envelope
Crystalline lattice of single protein

Question 13

What is the function of the proteinaceous S-layer?

Answer 13

Protective, selective sieve

Question 14

Why is the protective S-layer often lost in lab strains?

Answer 14

Bacteria can survive without it/ no longer need it

Question 15

What are capsules made from?

Answer 15

Usually polysaccharide

Question 16

What is the role of bacterial capsules?

Answer 16

Avoidance of immune response

Question 17

What are pili and fimbriae made from?

Answer 17

Protein polymers

Question 18

What is the difference between pili and fimbriae? (2)

Answer 18

Pili are usually longer than fimbriae
Usually fewer pili

Question 19

What gives directionality to flagella?

Answer 19

Chemotaxis

Question 20

What are endospores triggered by?

Answer 20

Starvation

Question 21

What are biofilms?

Answer 21

Communities often with multiple species held together by a matrix

Question 22

What can a biofilm ‘matrix’ consist of? (3)

Answer 22

Mainly polysaccharide
Protein
Nucleic acids

Question 23

What is the function of biofilms? (2)

Answer 23

Adhesion
Resistance