Lc1: Bacteriology

Question 1

external structures bacteria

Answer 1

• Pili/fimbria are adherence proteins
   Also include sex pili that are needed in horizontal gene transfer (conjugation)
   Decide to which cells of the host they can infect
• Capsule made out of carbohydrates used in adherence, protection against phagocytosis and against antibiotics
• Flagellum protein structure used for movement

Question 2

cell wall

Answer 2

Composed of peptidoglycan –> alternating (disaccharides) N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM) linked with chains of amino acids

Question 3

peptidoglycan synthesis

Answer 3

1. Bacterial enzymes called autolysins break the glycosidic bonds between the peptidoglycan monomers at the point of growth along the existing peptidoglycan and break the peptide cross-bridges that link the rows of sugars together
2. The peptidoglycan monomers are synthesized in the cytosol and bind to bactoprenol.
3. The bactoprenols transport the peptidoglycan monomers across the cytoplasmic membrane and interacts with transglycosidases to insert the monomers into existing peptidoglycan
4. Transglycosylase enzymes insert and link new peptidoglycan monomers into the breaks in the peptidoglycan
5. Finally, transpeptidase enzymes reform the peptide cross-links between the rows and layers of peptidoglycan to make the wall strong

Question 4

gram-positive bacteria

Answer 4

Gram positive bacteria have lipoteichoic acids (phosphorylated sugars) which are important in adherence and virulence

Question 5

gram-negative bacteria

Answer 5

• Gram negative bacteria have lipopolysaccharides (lipids and sugars)
• Inflammation & shock
• Endotoxin
• Consists of lipid A (anchor into membrane), inner core, outer core and an O antigen (O antigen is used to check which strain of bacteria we are dealing with very specific antigen  serotyping)

Question 6

virulence

Answer 6

Virulence is the relative capacity of a pathogen to overcome body defences

Question 7

quorum sensing

Answer 7

• Bacteria can change their phenotype depending on the amount of bacteria in a given area
• Bacteria secret acyl-homoserine lactone (AHL) which functions as a signalling molecule
• When there are many bacteria close to each other they get and give each other many signalling molecules:
• When a signalling molecules enters a bacterium it can bind to a protein and then bind to a promotor of genes that only need to be active when a sufficient amount of bacteria are present (like luciferase  glowing protein)
• Especially biofilm is important (biofilm)

Question 8

HGT

Answer 8

• gaining virulence factors to go from commensal to pathogen
• via MGE like plasmids, transposons or integrons
• Conjugation –> sex pili
• Transformation –> naked dna
• Transduction –> phages
  vesiduction

Question 9

antibiotics

Answer 9

• Antibiotics utilize the differences between eukaryotic host cells and bacterial cells
• Bacteriostatic antibiotics prevent replication of bacteria  giving the host immune system an opportunity to figth the infection
• Bactericidal antibiotics actively kill the bacteria

macrolides –> 23S ribossmal unit inhibition
(fluor)quinolones –> inhibit topoisomerase
beta-lactams –> inhibit peptidoglycan synthesis enzymes
sulphonamides –> anti metabolite
aminoglycosides –> inhibit protein synthesis