Week7_Section_Nhat_key-1 - Nhat Pham BIMM120...

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Nhat Pham  BIMM120 nmpham@ucsd.edu 11/16/09 OH: Mon 5pm-7pm Bonner 3126 Handout #7 DISCUSSION 1. List the classification of bacteria (e.g. psychrophile, thermophile, etc.) based on  the temperature, water activity, pH and pressure of their natural environment.  Describe some trends among organisms regarding these factors (for example:  most thermophiles are__________ than non-thermophiles) Temperature: Psychrophile: grow at low temperature (0 o C) Mesophile: grow at medium temperature For most pathogens, optimal growth occurs at 37 o C (human body  temperature) Thermophile: grow at temperature greater than 55 o C Examples: bacteria that live in compost pile or haystack Bacillus infernicus : thermophiles that release heat underground. Extreme thermophile: grow at temperature between 65 o C to 110 o C (found in  thermal vent and hot springs) The most thermophilic prokaryotes are certain archaea species These organisms have enzymes that are stable at high temperature Example: Taq DNA polymerase from  Thermus aquaticus  -> used in PCR General trend: Structurally less complex organisms can grow at higher temperature than  can more complex organisms -> Prokaryotes and nonphototrophic organisms can grow  better at higher temperature than eukaryotes and phototrophic organisms. Water activity:  measure of the availability of water in the environment The order of minimal water activity needed for growth is: Most Bacteria > Many  Yeast > Many Molds > Halophilic (salt-loving) bacteria > Xerotolerant (dryness tolerating)  Fungi > Osmophilic Yeasts (grow well in environment with high concentration of solute)
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This note was uploaded on 04/29/2010 for the course PSYCH PSYCH 179 taught by Professor Koob during the Fall '09 term at UCSD.

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Week7_Section_Nhat_key-1 - Nhat Pham BIMM120...

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