Prokaryote cell biology 2

• what is a plus

  straight and relatively rigid cell extensions
• features of pili

  • 100-1000 per cell, 1-2 µm long and 2-8 nm wide
  • Pili are dynamic, they can retract and grow
  • Pili function in DNA exchange between cells and surface adhesion
• structure of a plus

  • Pili are thin polymers of one protein (pilin)
  • Pilin molecules interact via hydrophobic extensions
  • The biogenesis of bacterial adhesion pilli (P-pili)
  • The un-polymerized pilin protein forms a complex with a chaprerone to protect the hydrophobic extension
• what is the gliding mechanism of Myxococcus xanthus

  1. The Glt complex bridges the cell envelope and moves along the cell length
  2. This motility is powered by the Agl motor
  3. The motor is anchored to the peptidoglycan in the periplasm
  4. Agl uses the proton gradient to move along helical MreB filaments
  5. Glt complex is anchored to an focal adhesion complex
  6. The Focal adhesion complex interacts with secreted "slime"(polysaccharides)
  7. This interaction with the "slime" immobilises the machinery but moves the cell forward
• what triggers actin polymerisation in listeria

  • ActA resembles a host protein that triggers actin polymerisation
  • The bacterium uses the endogenous machinery to make an actin "comet tail".
• evidence that ActA mediates motility

  point mutation in ActA affects Listeria motility
• which of the 6 known secretion systems in gram negative bacteria injects proteins

  3, 6
• Similarities between the rotation motor of flagella and type III Secretion System (TTSS)

  Both assemblies share homologous proteins
• how do bacteria inject host cells

  • Secretion induced by contact with host (lipid recognition) or abiotic clues (oxygen, calcium changes, temperature changes)
  • Rings of proteins assembles into a "needle”
  • The "needle" injects proteins into the host cell
  • Bacteria force the host cell to take them up