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Quiz 6 Microbiology
| Question | Answer |
|---|---|
| How is the O-F glucose test differential? (What it tells us?) | Tells us how much a microbe used glucose through fermentation (anerobic) or through oxidation (aerobic) |
| Why we need 2 test tubes for O-F glucose test? | One tube will be aerobic so oxygen can reach the bacteria One tube will be anaerobic so oxygen is blocked and cannot reach the bacteria. |
| How did we create an anerobic test tube? | added a layer of sterile mineral oil on top of the medium |
| Which tube tells us about oxidation of glucose? | aerobic tube without mineral oil |
| Which tube tells us about fermentation of glucose? | Aerobic tube without mineral oil |
| What does a positive result for carbohydrate use look like? | Yellow (glucose use= ACID) |
| What does a negative result for carbohydrates use look like? | Green (or slightly blue) |
| The results of a O-F test when both tubes are green mean? | GLucose was not used by the microbe |
| The results of a O-F test when both tubes are yellow mean? | GLucose was used by the microbe under both aerobic (oxidation) and anaerobic (fermentation) conditions (**microbe may have been able to perform fermentation under aerobic conditions also) |
| The results of a O-F test when sealed tube is yellow, unsealed tube is green means? | Microbe performed fermentation but not oxidation |
| The results of a O-F test when sealed tube is green, unsealed tube is yellow? | Microbe performed oxidation but not fermentation |
| What does Catalase breakdown? | Hydrogen peroxide |
| What are the 2 products that Catalase produces? | Oxygen gas (bubbles) and water |
| What causes the bubbling of a positive catalase reaction? | Production of Oxygen gas |
| What is the benefit of an organism having the enzyme Catlase? | Organisim can detoxify hydrogen peroxide,, which is reactive oxzygen species (ROS) that would otherwise damage/kill the cell |
| When are toxic forms of oxygen usually created? | During the electron transport chain |
| How does oxygen become toxic? | Oxygen is partially reduced (recevies one electron) instead of fully reduced (recevies two electrons) |
| Why are Hydrgoen peroxiude and the superoxide radical hgarmful to cells? | Anaerobic organsisms cannot detoxify ROS |
| How are the Hydrogen peroxide and trhe superoxide radical harmful to cells? | ROS will oxidize (steal electrons from_ proteins, DNA, cell membrane, etc. to fills its outer electron shell with electrons. This willl ultimatley lead to cell death. |
| Why isn't this effect seen in aerobic organisms? | Aerobic organisms have enzymes to detoxify ROS |
| How does catalase detoxify hydrogen peroxide? | Catalase converts hydrogen peroxide into water and oxygen gas (O2) |
| What does a positive result for the catalase test look like? What causes the apperance of the positive result? | Bubbles= positive results Bubbles= production of Oxygen gas |
| Wjat does a negative test for the catalase test look like? | No bubbles = negative results |
| What does the Oxidase test tells us? | If microbe's electron transport chain contains Cytochrom C oxidase |
| Where is Cytochrome C oxidase found inside of cells? | 4th protein in eelctron tranport chain |
| What is the normal function of Cytochrome C Oxidase? | Transfers electrons from Cytochrome C to Oxygen (final electron acceptor) |
| What does a positive oxidase test look like? | Turns bluish-purple |
| What does a negative oxidase result look like? | No color change |
| What makes BE Agar selective? | BIle salts prevent growth of non-enteric species |
| What is Esculin? | Glucose and Esculetin connected with glycosidic bond |
| Why would it be benefical for an organism to break down Esculin? | Breaking down Esculin releases glucose, which can be used to make ATP |
| What does a positive BE result look like? | Medium turns brownish-black |
| What is the purpose oif ferric citrate in the BE media? | Ferric Citrate is oxidized iron that interacts with Esculetin (if present), causing a color change to indicate esculin breakdown |
| What specifically causes darkening of the BE media? | Interaction between ferric citrate and esculetin |
| How does feriic citrate show a positive result? | By interacting with esculetin |
| What Gram posititve organisms show postive BE results? | Enterococcus speciesb and Group D Streptococci |
| What Gram negative organisms show a positive BE result? | Klebisalla, Enterobacter, and Serratia |
| What does a negative BE result look like? | No color change in the medium |
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