The structures of the bacterial cell surface 2

Question 1

Diff between gram +ve and gram -ve cells?

Answer 1

+ve has a thicker cell wall

Question 2

How can peptidoglycan be modified?

Answer 2

Variations to its basic structure
Variations in the AAs in the side chain
Modifications to the glycan backbone

Question 3

What can variation in peptidoglycan lead to?

Answer 3

Immune evasion and different responses to antibiotics

Question 4

Examples of modifications to the glycan backbone?

Answer 4

O-acetylation
N-deacetylation
N-glycosylation

Question 5

What variation does S.aureus have?

Answer 5

There is a pentaglycine interbridge between D-ala and L-Lys instead of a peptide crosslink between d-ala and DAP

Question 6

What do teichoic acids do?

Answer 6

Adds -ve charge to the cell wall

Question 7

Different types of teichoic acids?

Answer 7

Wall teichoic acid
Lipoteichoic acid

Question 8

Effect of D-alaynating a teichoic acid?

Answer 8

Changes -ve charge to a +ve

Question 9

Roles of outer membrane?

Answer 9

Interface to external environment
Nutrient uptake
Adherence
Barrier to and evasion of host defence
Resistance to harmful molecules

Question 10

How is the outer membrane attached to the cell wall?

Answer 10

Via lipoproteins

Question 11

Tripartite structure of lipopolysaccharide?

Answer 11

Lipid A, core polysaccharide, repeating unit/O antigen

Question 12

What is lipopolysaccharide recognised by?

Answer 12

Toll like receptor 4

Question 13

Two main important features of a lipoprotein?

Answer 13

Lysine at the end that attached to the cell wall
Cysteine residue that attaches to the outer membrane

Question 14

What is a capsule?

Answer 14

Polysaccharide layer, often covalently attached to the cell

Question 15

What is a slime layer?

Answer 15

DIffuse layer of polysaccharides, not covalently attached

Question 16

What makes up the Streptococcus pneumoniae vaccine?

Answer 16

Different types of the capsule of the bacteria

Question 17

What are the benefits to a bacteria of varying its cell surface?

Answer 17

Energy saving, adaptation to a new environment, evading the immune system

Question 18

Which type of bacteria dont always have a cell wall?

Answer 18

Intracellular bacteria

Question 19

Possible issue for bacteria that have peptidoglycan?

Answer 19

PG stimulates the immune system

Question 20

How do some bacteria function w/o a cell wall?

Answer 20

osmotic protection from living in another cell, v stable cytoplasmic membranes

Question 21

What do bacteria that done have a cell wall often contain?

Answer 21

Sterols and lipoglycans
Cross linked cysteine rich proteins

Question 22

What is an L form bacteria?

Answer 22

Bacteria that normally has a cell wall, but it is stripped away using a cell wall hydrolase

Question 23

Difficulty w/ acid fast bacteria?

Answer 23

Waxy layer of mycolic acid so makes it impermeable to antibiotics and other chemicals

Question 24

What cell wall modification does streptococcus pneumoniae have?

Answer 24

Choline binding proteins

Question 25

What cell wall modification does bacillus anthracis have?

Answer 25

S layer--> crystalline structure on the surface of the cell, protects it from everything