microorganisms that cause illness or disease |
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pathogens |
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3 places foodborne illnesses come from |
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presence of pathogens in IT, the production of a toxin by a path. in the gut, ingestion of a toxin from growth on food |
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most foodborne illness result in ____, but can be especially dangerous in _____. |
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diarrhea
children, elderly and immunocompromised |
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found in animal intestines especially poultry, transmitted in uncooked meat |
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camplyobacter jejuni |
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an infection of camplyobacter jejuni causes: |
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fever, headache, muscle pain, diarrhea, abdominal pain and nausea |
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found in intestines of birds or mammals, transmitted in undercooked eggs,meat, and milk |
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salmonella |
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a salmonells infection causes: |
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fever, chills, aches, abdominal pain, and may be serious if it spreads to blood |
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found in the intestines of mammals(cattle) |
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Escherichia coli |
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an e.coli infection causes: |
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diarrhea, dysentery, kidney failure, blindness, paralysis, death |
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most foodborne illnesses are caused by: |
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fecal-oral cycle pathogens |
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the USDA's standard for maximum permissible number of bacterial cells in hamburger is:10 |
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10^7 cells/gram |
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hamburger should be cooked to: |
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160 degrees Farenheit |
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in the hamburger contamination lab, what type of medium did we use? |
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3M petrifilm cultures to get a total aerobic bacteria count and a coliform count |
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What volume of liquid is used to inoculate a 3M Petrifilm culture? |
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1.0 ml |
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A 0.1ml aliquot of a 10-2 dilution of the sample gives 90 colonis.What is the concentration of coliform bacteria? |
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9.0 x 10^2 |
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On a 3M Petrifilm culture for E.coli, a colony of a fecal coliform appears: |
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blue and is associated with gas bubbles |
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What is the term for microorganisms that can grow and cause food spoilage in the refrigerator? |
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psychrophillic |
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What type of microorganism is Penicillium? |
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fungus (mold) |
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The food preservative sodium nitrite is: |
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an inhibitor of pyruvate-ferrodoxin oxidoreductase |
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Nitrites are added to meat because it gives meat a pink color and inhibits: |
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Clostridium botulinum |
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How do propionate and benzoate prevent microbial growth? |
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They increase the proton concentration of the cytoplasm in microbes. |
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Which one of the following substances is not classified as a disinfectant? bleach, alcohol, phenol, tetracylcine |
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alcohol |
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An antiseptic is |
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an antimicrobial substance that is used to kill or inhibit microorganisms on the skin |
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chemical disinfectants are more lethal to bacteria at ______ |
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higher concentrations |
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____ was used as a disinfectant in hospitals for many years. |
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phenol |
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The Snyder Test is used to: |
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check for high numbers of glucose-fermenting, acid-tolerant bacteria in saliva. |
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Snyder Test Agar will turn fully yellow only if the pH drops below: |
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3.8 |
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In ethanol fermentation yeast produce one molecule of ___ for every molecule of ethanol they make. |
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CO2 |
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Both ethanol and lactic acid can inhibit: |
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the growth of undesirable microorganisms in food products. |
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The predominant sugar found in grape juice is: |
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sucrose |
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The production of yogurt is an example of: |
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a microbial succession that primarily involves two species of bacteria. |
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process of yogurt production: |
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scald milk to 80C, allow to cool below 65C, add commercial yogurt, incubate at 43C |
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if 100 grams of sugar is converted to ethanol in 100% efficient reaction, the yeast produces: |
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51 grams of ethanol and 49 grams of carbon dioxide |
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Yogurt production primarily involves: |
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the fermentation of milk sugar,lactose, to produce lactic acid. |
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What two bacteria are used to make yogurt? |
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Lactobacillus bulgaricus and Streptococcus thermophilus |
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nitrite converted to nitrate is: |
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an oxidation reaction |
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ammonia converted to nitrite is: |
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an oxidation reaction |
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nitrate converted to elemental nitrogen (N2) is: |
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a reduction reaction |
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elemental nitrogen (N2) converted to ammonia is: |
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a reduction reaction |
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The oxidation of ammonia to nitrate is called: |
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nitrification |
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Nitrosococcus bacteria can produce energy by oxidizing: |
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ammonia to nitrate |
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Some strains of Pseudomonas bacteria can reduce: |
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nitrates to nitrogen gas |
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The enzyme urease breaks down urea to: |
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ammonia and CO2 |
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The breakdown of amino acids and other nitrogen-containing organic compounds to release ammonia is called: |
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mineralization |
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Trommsdorf reagents produce a ____ color when they react with nitrite (NO2-). |
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dark blue inky |
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Trommsdorf reagent ___ can burn your skin or cause holes to appear in your clothing. |
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II |
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For the nitrate reductase test, a color change to blue after the addition of zinc indicates a: |
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NEGATIVE test result (nitrate was not reduced by the bacteria). |
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For the ammonia oxidation test, a color change to blue after addition of zinc indicates a: |
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POSITIVE test. (Bacteria oxidized the ammonia completely to nitrate.) |
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Trommsdorf reagents do not react with: |
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ammonium |
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Nitrification is also called: |
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ammonia oxidation |
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Nitrification is a two-step process. ____ carries out the first step while ____ carries out the second step. |
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Nitrosomonas,Nitrosococcus, & Nitrosospirina/ nitrobacter,nitrosococcus, and nitrospira |
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Nitrification is an: |
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aerobic process |
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nitrification ____ energy (ATP) |
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produces |
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Denitrification is an: |
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anaerobic process |
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Mammals excrete excess nitrogen primarily in the form of: |
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urea |
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most bacteria and aquatic animals excrete excess nitrogen in the form of: |
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ammonia |
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The main carbon source in the ammonia broth used in Experiment 19C is: |
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carbonate |
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The carbon source in nitrate broth (Ex. 19b) is: |
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a mixture of organic compounds |
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The only organisms that can convert elemental nitrogen (N2) to organic forms are: |
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certain prokaryotes |
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why is hamburger especially subject to contamination by pathogens? |
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the chopping process mixes anny surface bacteria that are present as well as air in with the meat |
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name the bacteria that cause foodborne illness: |
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camplyobacter jejuni, clostridium botulinum, clostridium perfringens, e.coli, salmonella, listeria monocytogenes, shigella, staph. aureus |
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for hambuger contamination lab, what tubes did you use for the uncooked meat and what were they labeled? |
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three 9.9ml and one 9.0ml tubes of saline, 10^-3, 10^-5, 10^-7, and 10^-6 |
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in hamburger contamination lab, what tube did you use for the 120 degree meat and the 160 degree meat? |
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9.9ml saline tube for the 10^-3 120 degree, and 9.0ml saline tube for the 10^-2 160 degree |
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at what temperature do you incubate the 3M petrifilms? |
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37 degree C |
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how do you calculate the total number of cell/gram of meat? |
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dilution facter X number of colonies |
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spoilage from microorganisms causes a loss of up to ___% of all food grown for human consumption |
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40% |
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small organic acids from carbohydrates can cause food to tast ____. |
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sour |
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longer chain fatty acids made ffrom the breakdown of fats can cause a food to taste ____. |
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rancid |
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the breakdown of proteins can yield ammonia, amines, and hydrogen sulfide that make food ____. |
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putrid |
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physical methods for controlling microbial growth on food: |
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heat (dry,moist, or pasteurization), filtration, desiccation, osmotic pressure and radiation (ionizing and nonionizing) |
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sulfer-based preservatives |
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sulfites |
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when looking at the diameter of a mold colony: |
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the smaller the diameter, the more effective the preservative was |
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a paper disk is soaked with a substance and placed on the surface of an agar medium that has been uniformly inoculated with a microorganism |
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disk diffusion test |
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factors that affect the size of the zone of inhibition observed in a disk diffusion test |
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concen. of the antimicrobial agent, substance being tested,species of microorganism tested,rate of diffusion of substance through agar, conditions |
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what fermentable sugar and pH indicator dye are in the Snyder test agar? |
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dextrose (glucose), bromcresol green |
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difference between snyder test agar and OF-glucose agar |
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starting pH of snyder is more acidic (4.8), snyder will not turn yellow until it reaches a much lower pH |
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from of anaerobic metabolism in which the terminal electron acceptor, or oxidizing agent, is an organic compound. |
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fermentation |
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process in wine production where dead yeast cells settle to bottom and are transferred to different tank. |
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racking |
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what does scalding the milk do in yogurt production? |
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it will kill any contaminating bacteria, drive off oxygen to enhance anaerobic conditions, and reduce water content |
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how do you calculate to mass of alcohol produced |
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multiply the mass of carbon dioxide lost by 1.045 |
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the conversion of atmospheric nitrogen (N2) to ammonia is caled: |
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nitrogen fixation |
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use of nitrogen or ammonia by incorporating into amino acids or proteins, opposite of mineralization |
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nitrogen assimilation |
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process of reducing nitrate to ammonia except that nitrogen is not lost from the soil |
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assimilatory nitrate reduction |
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nitrogen fixation is catalyzed by the enzyme: |
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nitrogenase |
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chemistry of trommsdorf reagents |
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sulfuric acid in II react with nitrite to produce nitrous acid which then reacts w/ iodide to form iodine, starch in I from blue complex with iodine |
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a yellow-orange result for urea broth indicates: |
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a negative result, does not degrade urea to ammonia |
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a bright pinkish-red result for urea broth indicates: |
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a positive result, degrades urea to ammonia |
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for hamburger lab, TA prepares the 10^-1 sample by: |
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mixing 10G of hamburger with 90ml of sterile saline |
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what organism was used to contaminate hamburger? |
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e.coli |
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for the aerobic plate count petrifilms, you use the ____ side of the spreader to distribute the sample |
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recessed |
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for the viable plate count, what volume do you spread on the petri plates? |
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0.1ml |
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to estimate the number of colonies on aerobic petrifilms: |
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count the number of colonies in 2 squares, average them, and multiply by 20 |
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how many petri plates do you use for ex. 16 (food preservatives)? |
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8 |
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how much 2% propionate stock solution should you add tot he petri dish in order to get a final concentration of 0.3%? |
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3.5ml |
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how long do you wait after mixing agar w/ preservatives before moving or inoculating the plate? |
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15 to 20 minutes, then inoculate |
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what technique should be used to inoculate potato dextrose agar w/ penicillium? |
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place a drop in the center of the plate and allow to dry |
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penicillin and tetracycline are: |
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antibiotics |
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alcohol, tincture of iodine, and bactine are: |
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antispetics |
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for ex.17 you prepare two plates of: |
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s.epidermis and e.coli |
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the negative control for ex. 17 is: |
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a drop of water |
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for ex. 17, how much solution do you add to the plates to test? |
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5 microliters |
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for the snyder test, what do you do to distribute sample throughout tube? |
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roll gently between hands |
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snyder test is incubated for: |
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more than 25 hours |
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sugar used in agar medium for growing lactic acid: |
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lactose |
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sugar used in PDA, the agar for growing yeasts, is: |
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glucose |
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how much sugar is present in 8oz. of Welch's grape juice? |
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40 grams |
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how much sugar do you add to the grape juice? |
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30 grams |
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how much warm water do you use to activate the yeast? |
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50ml |
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how much yeast do you put into the grape juice? |
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2-3 grams |
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on day 1 of wine production, you take a sterile loop of the mixture and: |
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streak a PDA plate |
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what days do you check pH for wine production? |
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day 1 and 5 |
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what days do you calculate ethanol production for wine ex.? |
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day 5 |
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what days do you smell the mixture to detect ethanol production in wine? |
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days 2,3,4 and 5 |
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what days do you observe the bottle of wine to detect gas? |
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days 2,3,4 and 5 |
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metallic zinc can reduce nitrate to: |
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nitrite |
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when setting up urease test in 19a, you inoculate urea broth with: |
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4 loopfuls |
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used in 19b to inoculate both nitrate and PBE broths but not in 19a: |
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pseudomonas aeuignosa |
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show a positive result in urease test: |
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proteus vulgaris |
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used to inoculate 2 tubes of ammonia broth in 19c, one gets air and one does not: |
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soil |
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shows a negative result in the urease test: |
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serratia marcescens |
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linear plots plot: |
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Log AU vs. time |
| |
semi-log plots plot: |
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AU vs. time |
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takes over when the pH drops below 5 in yogurt production: |
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lactobacillus bulgaricus |
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gros most udring the late stage of yogurt production: |
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lactobacillus bulgaricus |
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glutamic acid is made from alpha-keto-glutarate plus ammonia: |
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nitrogen assimilation |
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