Bacteriology from PID

• How does bacteria grow

  • Binary fission = bacteria cell grows and replicates DNA, divides up DNA but not always evenly, splits.
  • Simple process therefore can be rapid
  • Phases of growth = lag, log, stationary, death
• Cell wall

  • Made of peptidoglycan
  • Either gram-ve or gram+ve
  • Gram +ve has thick peptidoglycan layer - purple stained
  • Gram -ve thinner peptidoglycan layer which is sandwiched between membranes, pink stained, has structures such as LPS on cell surface
• Bacterial surface structures

  • Fimbriae = adhesion
  • Pilli = adhesion, genetic exchange
  • Flagella = motility
• Innate immune system recognition

  • PAMPS
  • PRRs
• Innate immune cells which can destroy bacteria

  • Phagocytes
  • Neutrophils
  • Macrophages
  • Dendritic cells
• Ways bacteria pass on genetics

  • Horizontal gene transfer - pass genetic info from one bacteria to another (main driver of genetic variation in bacteria)
  • Vertical gene transfer - binary fission
• • If low cell density = quorom sensing will not work
  • If high cell density = they might trigger to say there's quite a lot of us now let's stop growing, let's not take it up food. Let's stop taking up nutrients. They stop taking up oxygen because if we keep doing it, we're going to die because there's not going to be enough for us.
• Bacteria need to co-ordinate the expression of virulence factors for successful pathogenicity and this is done by quorum sensing.