12-13_Microbial_Growth___Metabolism_Combo

• obligate – die in presence of oxygen it is

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Unformatted text preview: • Obligate ____________ – Die in presence of oxygen. It is poisonous to them. Anaerobic respiration = break down food into useable energy without the use of O2. • _____________ Anaerobes – Not strict aerobes or anaerobes. Many yeasts and enteric bacteria. Escherichia coli and Staphylococcus aureus. • ________________ bacteria – Require oxygen levels lower that that found under normal atmospheric conditions ( Helicobacter pilori – found in stomach). • ________________ Anaerobes – Don’t use oxygen, but are not killed by it. (Lactobacilli - This genus will make pickles from cucumbers and cheese from milk.) Microbes & Oxygen O 2 From the Virtual Microbiology Classroom on ScienceProfOnline.com Microbes & Oxygen Aerobic and anaerobic bacteria can be identified by growing them in liquid culture: 1: Obligate aerobic bacteria gather at top of test tube to absorb maximal amount of oxygen. 2: Obligate anaerobic bacteria gather at bottom to avoid oxygen. 3: Facultative anaerobes gather mostly at the top, since aerobic respiration is most beneficial; but as lack of oxygen does not hurt them, they can be found all along the test tube. 4: Microaerophiles gather at upper part of test tube, not at top. Require O 2 , but at low concentration. 5: Aerotolerant bacteria are not affected by oxygen, and they are evenly spread along the test tube. Image: Microbial oxygen requirements , Pixie From the Virtual Microbiology Classroom on ScienceProfOnline.com Using oxygen (1/2 O 2 ) in metabolism creates toxic waste. Microbes that are able to use aerobic respiration produce enzymes to detoxify oxygen: Catalase : H 2 O 2---  H 2 0 and 0 2 Superoxide dismutase (SOD): oxygen radical ---  H 2 0 and O 2 Microbes that don’t make these enzymes cannot exist in the presence of oxygen. Microbes & Oxygen Image: Catalase enzyme structure , Vossman; Superoxide dismutase enzyme structure , Fvasconcellos From the Virtual Microbiology Classroom on ScienceProfOnline.com Microbes & Temperature _____________ • Three-dimensional shape because of the temperature sensitive hydrogen bonds. • These bonds will usually break at higher temperatures, and protein become ________. • Denatured proteins lose function. ____________ Also temperature sensitive. Become brittle if temperature is too low. If temperature too high, lipids will be more liquid in form. Outside membrane cannot preserve the integrity of the cell and it will disintegrate. Images: Superoxide dismutase enzyme structure , Fvasconcellos; Phospholipids & Cholesterol , Cytochemistry.net From the Virtual Microbiology Classroom on ScienceProfOnline.com Effects of Temperature on Growth 95 o F 77 o F 40 o F Most of our plates are incubated at 37 o C (98.6 o F). Conversion C to F = 1.8 x C + 32 From the Virtual Microbiology Classroom on ScienceProfOnline.com Categories of Microbes Based on Temperature Range Gram positive , rod-shaped _________________....
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• Obligate – Die in presence of oxygen It is poisonous...

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