Read the summary and the most important questions on 2.2 Microbial components influencing host physiology | Erwin G. Zoetendal

• 1 Microbial surface molecules

  This is a preview. There are 1 more flashcards available for chapter 1
  Show more cards here

• How are host-microbe interactions studied?

  Germ-free animals and epithelial cell lines are used, since they can be inoculated with controlled (mono-) cultures of microbes.

• What are bacterial impacts on the gut-brain axis (3)?

  1: activation of neural afferent circuits to the brain

  2: activation of mucosal immune responses

  3: production of metabolites that directly influence the CNS

• What is the structure of a Gram-positive  and a Gram-negative cell envelope?

  Gram-positive: cytoplasmic membrane - thick peptidoglycan layer
  Gram-negative: cytoplasmic membrane - thin peptidoglycan layer - outer membrane

• How are Gram-positive bacteria recognized by the host?

  Lipoteichoic acids (LTA) in the PG layer can bind to TLR2
  knock-out of D-alanine in LTA: pro-infl. -> anti-inflammatory response
  Peptidoglycan can bind to TLR4

• What is the structure of LPS of Gram-negative bacteria?

  Recognized by TLR4
  O-specific polysaccharide: variable among G- bacteria, used for recognition
  Core polysaccharides
  Lipid A: endotoxic

• Name 3 other envelope structures and their functions.

  1: flagellum: motility
  2: fimbriae: attachment
  3: pili: attachment, conjugation (DNA transfer)

• What are contingency genes, and how do they work?

  Genes with a higher mutation rate -> adaptation to changing environment
  i.e.: fimbriae: necesaary for host infection, but prone for immune recognition
  strand slipping: nucleotide sequence is repeated, copy on homologues strand pair out of register. Leads from single base deletions to larger deletions.

• 2 Metabolites

  This is a preview. There are 5 more flashcards available for chapter 2
  Show more cards here

• What are the 3 pathways of carbohydrate degradation?

  Complex polymers -> [hydrolysis] -> monomers -> [primary fermenters] -> 1: acetate ->
  2: H2, CO2 -> [Acetogenesis] -> acetate ->
  3: propionate, butyrate, succinate, alcohols -> [syntrophy] -> H2, CO2 + acetate ->
  -> [methanogenesis] -> CH4, CO2

• Give a model of cross-feeding in the small intestine.

  glucose -> [Streptococcus] -> lactate -> [Veilonella] -> propionate, acetate -> host
  glucose -> [E. coli] -> acetate (+ lactate) -> [Clostridium] -> butyrate -> host

• What are the 3 propionate production pathways?

  Via acrylate, succinate or propanediol