4.4.2 physical conditions of growth -> water and osmotic pressure

what is water activity?

Water activity, Aw decreases when solute concentration increases

what is the Aw of pure water?

Aw of 1.0

what is the Aw of bacteria?

Aw of 0.96 and above

what is the Aw of yeast and molds?

Aw of 0.9 and below

what is the Aw of xerotolerant microbes?

Aw as low as 0.6

what is osmotic pressure?

the pressure exerted on the semi-permeable membrane by the solution

what are the different effects of different solute concentrations on cell?

hypertonic

hypotonic

what is hypertonic

net loss of water, plasmolysis

what is hypotonic

net gain of water, if no cell wall, lysis

what do halophiles require?

require higher salt concentrations to grow

halophiles is typically relate to?

marine microbes, seawater

how much can halophiles tolerate?

some can tolerate up to 20 to 30% salt

what is an example of halophiles

staphylococcus aureus