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Micro-Lab002
Aerotolerance
| Question | Answer |
|---|---|
| What is thioglycolate broth used for? | To differentiate oxygen requirements. |
| Where do obligate aerobic (oxygen-needing) bacteria gather on a thioglycolate broth? Why? | at the top of the test tube in order to absorb maximal amount of oxygen. |
| Where do obligate anaerobic bacteria gather on a thioglycolate broth? Why? | at the bottom, to avoid oxygen. |
| Where do facultative bacteria gather on a thioglycolate broth? Why? | at the top, since aerobic respiration is the most beneficial one; but, as lack of oxygen does not hurt them, they can be found all along the test tube. |
| Where do microaerophiles gather on a thioglycolate broth? Why? | at the upper part of the test tube but not at the top. They require oxygen but at a low concentration |
| Where do aerotolerant bacteria gather on a thioglycolate broth? Why? | they are evenly spread along the test tube because they aren't affected at all by oxygen. |
| Why don't you shake the thioglycolate broth? | Shaking would add more oxygen to the tube than thioglycolate could absorb |
| What should you do to salvage it if you do shake it? | Vigorous heating will boil out dissolved gases |
| What causes condensation on the sides of the anaerobic jar? | Basically: H20-2 hydrogen's, 1 oxygen. Water is formed from 2 hydrogens attaching to every oxygen molecule to form water. Answer on paper: atmospheric oxygen and hydrogen liberated from the GasPak. |
| Why can't you do a catalase test on organisms grown on blood agars? | Blood cells are catalase positive and will bubble if H2O2 (hydrogen peroxide) is added, regardless of whether or not the organism growing on top of it is catalase negative or not. |
| What is the oxygen requirement category for: Alcaligenes | aerobe |
| What is the oxygen requirement category for: Clostridium | obligate anaerobe |
| What is the oxygen requirement category for: Enterococcus | aerotolerant anaerobe |
| What is the oxygen requirement category for: Escherichia | facultative anaerobe |
| Can aerobic bacteria grow in the absence of Oxygen (O2)? Why or why not? | Yes, because aerobic bacteria may be able to use fermentation or anaerobic respiration. |
| What would you need to do to determine whether bacteria growing on a Petri plate (agar)from the Brewer jar (Jar with tight lid that stunk really bad when opened in class) are anaerobes (don't like oxygen)? | Subcultures from these colonies could be incubated aerobically (with oxygen) to determine whether they can grow in the presence of oxygen. If they can't, they're most likely anaerobic. |
| What does the appearance of a blue or pink color in a thioglycolate tube mean? | The blue or pink area on the surface is the area that's been exposed to the oxygen. It means the indicator has been oxidized (combined with oxygen) |
| Why will obligate anaerobes grow in thioglycolate? | The free sulfur will tie up atmospheric oxygen, leaving the bottom of the medium anaerobic. |
| To what do you attribute the odors (stench) of anaerobic (no air) decomposition? | To the organic molecules produced that have odors. These molecules include: indoles acids alcohols amines ketones inorganic compounds (ammonia & hydrogen sulfide) |
| Why is aerobic (with air) decomposition not stinky? | Produces only inorganic molecules, which are odorless. |
| How do oxygen requirements differ between Streptococcus and Escherichia, which are both described as facultative anaerobes in Bergey's Manual? | Streptococcus: stricly fermentative. Lacks an electron transport chain. Escherichia: can grow anaerobically by fermentation and aerobically by using oxygen as the final electron acceptor in respiration. |
| Between Streptococcus and Escherichia, which one could correctly be called an aerotolerant anaerobe? | Streptococcus |
| How can the aerobe Pseudomonas aeruginosa grow in the absence of oxygen? | Some strains of Pseudomonas aeruginosa are capable of using NO3– as the final electron acceptor in anaerobic respiration |
| The catalase test is often used clinically to distinguish two genera of gram-positive cocci,(Blank A) and (Blank B)It is also used to distinguish two genera of gram-positive rods (Blank c) and (Blank D) | Blank A: Streptococcus (catalase-negative) Blank B: Staphylococcus (catalase-positive) Blank C: Bacillus (catalase-positive) Blank D: Clostridium (catalase-negative) |
| Gram-positive rods with endospores example? | Clostridium |
| Gram-positive rods with no endospores example? | Lactobacillus |
| Gram-positive cocci example? | Enterococcus |
| Gram-negative rods with pointed ends example? | Fusobacterium |
| Gram-negative rods with blunt ends example? | Bacteroides |
| Gram-negative cocci example? | Veillonella |
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