140 - Topic 6 Notes

1 for thermophiles and hyperthermophiles to survive

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Unformatted text preview: concentration is an important contributor to this value. The higher the aw value, the easier it is for the microorganism to obtain water. If the solute concentration outside of the cell is lower than inside (i.e. high water concentration outside) then the water tends to diffuse into the cell. If the solute concentration is higher outside the cell, then the water tends to diffuse out of the cell. In nature, water activity is commonly influenced by the NaCl concentration. Halophiles: growth optimum above 1% NaCl, often requiring sodium for growth Halotolerant: can tolerate the presence of solute, but grow better in the absence of solute Fundamentals of Microbiology (Biology 140) Course notes Dr. Josh D. Neufeld Osmophiles: can grow in presence of high sugar Xerophiles: can grow in very dry conditions To cope with low water activity, many microorganisms are able to increase the internal solute concentration (Table 5.4). They do this by increasing the intracellular concentration of compatible solutes, which do not inhibit biochemical processes. Oxygen Effects on Microbial Growth Please see Table 5.5 for an outline of how different microorganisms are affected by O2. Note that some organisms are very sensitive to O2, others require O2 for growth, and others can grow either in the presence or absence of O2. Note that reduction of O2 produces toxic byproducts, which are ve...
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This note was uploaded on 10/31/2011 for the course BIOL 140 taught by Professor Dr.joshneufeld during the Fall '10 term at Waterloo.

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