Sept 29, 2008 notes

Factors the influence bacterial growth

  • Osmotic Pressure
    • The pressure put on a cell because of the movement of water
    • Too little concentration of water sucks the water out of the bacterium, causing it to shrivel
    • Too much concentration of water flows into the the bacterium, causing it to explode
  • Water Activity
    • How much available water in given environment
    • Examples
      • pure water = 1.0 water activity (w.a.)
      • human blood = .995 w.a.
      • honey= .90 w.a. - S. aureus and S. epidermiditis can grow here!!
    • Bacteria can't survive if environmental conditions are too different from that bacteria's ideal growth conditions
    • Halophiles:able to survive in very low water activity
      • this ability comes from raising the concentration of solute on inside of cell
    • "Salt in a Wound"
      • Sucks the water out of bacterial AND our cells, so it HURTS because its killing our cells, but preventing infections.
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