The structures of the bacterial cell surface 2 Flashcards
Diff between gram +ve and gram -ve cells?
+ve has a thicker cell wall
How can peptidoglycan be modified?
Variations to its basic structure
Variations in the AAs in the side chain
Modifications to the glycan backbone
What can variation in peptidoglycan lead to?
Immune evasion and different responses to antibiotics
Examples of modifications to the glycan backbone?
O-acetylation
N-deacetylation
N-glycosylation
What variation does S.aureus have?
There is a pentaglycine interbridge between D-ala and L-Lys instead of a peptide crosslink between d-ala and DAP
What do teichoic acids do?
Adds -ve charge to the cell wall
Different types of teichoic acids?
Wall teichoic acid
Lipoteichoic acid
Effect of D-alaynating a teichoic acid?
Changes -ve charge to a +ve
Roles of outer membrane?
Interface to external environment
Nutrient uptake
Adherence
Barrier to and evasion of host defence
Resistance to harmful molecules
How is the outer membrane attached to the cell wall?
Via lipoproteins
Tripartite structure of lipopolysaccharide?
Lipid A, core polysaccharide, repeating unit/O antigen
What is lipopolysaccharide recognised by?
Toll like receptor 4
Two main important features of a lipoprotein?
Lysine at the end that attached to the cell wall
Cysteine residue that attaches to the outer membrane
What is a capsule?
Polysaccharide layer, often covalently attached to the cell
What is a slime layer?
DIffuse layer of polysaccharides, not covalently attached
What makes up the Streptococcus pneumoniae vaccine?
Different types of the capsule of the bacteria
What are the benefits to a bacteria of varying its cell surface?
Energy saving, adaptation to a new environment, evading the immune system
Which type of bacteria dont always have a cell wall?
Intracellular bacteria
Possible issue for bacteria that have peptidoglycan?
PG stimulates the immune system
How do some bacteria function w/o a cell wall?
osmotic protection from living in another cell, v stable cytoplasmic membranes
What do bacteria that done have a cell wall often contain?
Sterols and lipoglycans
Cross linked cysteine rich proteins
What is an L form bacteria?
Bacteria that normally has a cell wall, but it is stripped away using a cell wall hydrolase
Difficulty w/ acid fast bacteria?
Waxy layer of mycolic acid so makes it impermeable to antibiotics and other chemicals
What cell wall modification does streptococcus pneumoniae have?
Choline binding proteins
What cell wall modification does bacillus anthracis have?
S layer–> crystalline structure on the surface of the cell, protects it from everything
