Lecture 161. Recall what the cardinal temperatures are for bacterial growth a. Minimum- temperature under which bacteria cannot grow membrane gelling, transport processes slow and proteins in membrane cannot move around optimal- temperature at which growth is maximum enzymatic reactions occurring at maximal possible rate maximum- temperature over which growth stops protein denaturation, collapse of membrane thermal lysis2. Recall the names of the groups of microorganisms living in different temperature ranges a. Psychrophile ,20º Cb. Mesophile 20 < opt < 50ºCc. Thermophile 50 < opt < 80º Cd. Hyperthermophile opt T > 80º C3. Name a given microorganism based on its oxygen requirements a. Obligate aerobe- need oxygen to survive b. microaerophilic aerobe need oxygen, but an tolerate no more than 2%c. Facultative- can grow with or without oxygen, when present it will respire oxygen and grow faster with itd. Obligate anaerobe- Cannot tolerate oxygene. Aerotolerate Anaerobe- can grow with or without oxygen, but does not respire oxygen4. Name a microorganism based on where is grows in thioglycolate agar tube cultures a. Obligate aerobei. Only grows at top of tubeb. Obligate anaerobei. Only growth at bottomc. Facultative aerobe/anaerobei. Respiration- lots of ATP, grow very wellii. Fermentation- less ATP, less growthiii. Grow all over tubed. Microaerophilei. Only grow at low O2 levelse. Aerotolerant anaerobei. No respirationii. Fermentation even in presence of O25. Predict which protective enzymes a given microorganism is likely to have based on its oxygen requirements a. Aerobes- Catalase and super oxide dismutase (PRODUCE OXYGEN)b. Anaerobes- Peroxidase and super oxide reductase (PRODUCE HYDROGEN PEROXIDE) 6. Explain why certain protective enzymes are found in aerobes and facultative aerobes while other protective enzymes are found in anaerobes a. Microbes have enzymes that destroy these compoundsb. In aerobes and facultative aerobes: Superoxide dismutase and catalase (both produce O2)c. In anaerobes: Often superoxide reductase and peroxidase (do not produce O2)7. Explain what pH homeostasis is a. The ability to maintain neutral pH inside the cell in comparison to the outside of the cell8. Explain how variations in pH are used to protect food against spoilage a. If you change the pH to something the bacteria cant tolerant like in yogurt, it will stop bacterial growth9. Recall the classes of microbes that grow in environments with low water activitya. Xerophiles- Grow in very dry conditionsb. Osmophiles- Grow in high sugar conditionsc. Halophiles- Grow at high salt conditions 10. Explain how and why lower water activity is used to preserve foods from spoiling a. Metabolism slows down considerably without available water11. Describe the properties that a molecule should have to be a good compatible solute to protect microorganisms against hyperosmotic conditions a. Should be no toxic, should be highly soluble, should be able to not diffuse in and out of the cell12. Give examples of types of molecules often used by microbes as compatiblesolutes a. Amino acid type, carbohydrate type, alcohol
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