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Micro Lab 2 exam
microbiology
| Question | Answer |
|---|---|
| reduction | a gain of electron or hydrogen atoms |
| why does hydrogen peroxide bubble when poured on cut skin? | skin normal flora makes catalase |
| differentiate between aerobic and anaerobic respiration | aerobic- O2 is final electron acceptor anaerobic- inorganic compounds other than O2 is final electron acceptor |
| Differentiate between fermentation and anaerobic respiration. | Fermentation- organic compound is final electron acceptor Anaerobic respiration- inorganic compounds other than O2 are final electron acceptor |
| Would nitrate reduction occur more often in the presence or absence of O2? | Absence because if O2 was present,it would use O2 instead of nitrogen as the final electron acceptor |
| In nitrate reduction test, what does the presence of gas indicate? | Nitrate has been reduced to nitrate then to nitrous oxide then nitrogen gas (nitrate--->nitrite--->nitrous oxide--->nitrogen gas) |
| Is nitrate reduction beneficial or harmful to farmers? | nitrate reduction is harmful because plants need nitrates to survive. If nitrates are reduced to NO or N2, there is less available for the plants. |
| In the Nitrate reduction test, why did no color change appear after adding Nitrate A & B and zinc in P. aeruginosa? | The nitrates were reduced to nitrites then nitrous oxide and finally to nitrogen gas |
| When did E. faecalis exhibit color change in the nitrate reduction test? | There was no color change after nitrate A and B were added. It turned red after zinc dust was added |
| What is the purpose of the Respiration Lab? | To classify bacteria as aerobic or anaerobic. |
| what two organisms were positive for nitrate reduction? | P. aeruginosa and B. subtilis |
| What organism was positive and what organism was negative for the oxidase test? | E.coli was negative (did not have cytochrome c) P. aeruginosa was positive (contains cytochrome c) |
| what two organisms did we use in the catalase test? | E. faicalis and B. subtilis |
| What organism was positive in the Catalase test? | B. subtilis |
| The nitrate reduction test tests for what kind of organisms? | anaerobes |
| The oxidase and catalase test test for what kind of organisms? | aerobes |
| Why did we examine for gas production in the Nitrate reduction test? | If there is gas, the nitrate was reduced to nitrogen gas. |
| In what order is nitrate reduced to nitrogen gas? | nitrate-->nitrite-->nitrous oxide-->nitrogen gas |
| the chromosomal DNA of E.coli contains how many base pairs? | 3,000,000 |
| The DNA of E. coli is attached to what? | plasma membrane |
| What is the average fragment length of the large fragments of chromosomal DNA? | 100,000 to 200,000 base pairs |
| what is the average length of a gene? | 2000 base pairs |
| A convenient method for analyzing DNA of e. coli that consists of microscopic pores in the gel that act as a molecular sleeve | Agarose gel electrophoresis |
| where are the samples of DNA loaded into in the Agarose gel? | wells made in the gel during casting |
| Why does the DNA migrate towards the positive electrode? | DNA has a strong negative charge at neutral pH |
| How are the linear fragments of DNA separated? | The pores in the gel separate the linear fragments according to their size |
| Why does DNA appear as a smear? | If many fragments are present in a wide range of sizes it will appear as a smear (badly sheared DNA) |
| What is the objective of the Isolation of E.coli DNA lab? | to isolate bacterial chromosomal DNA with a minimum of breaks |
| The resuspended e. coli cells are first mixed with what solution? | EDTA |
| What forms complexes (chelates) with several kinds of metal ions? | EDTA |
| what kind of divalent metal cations are required cofactors by the majority of DNases? | Mg+2 |
| what dissolves the cell membrane and denatures many proteins? | sarkosyl |
| What degrades high molecular weight RNA? | RNase |
| what proteolytic enzyme is added to the cell lysate in order to digest proteins that are free in solution or bound to DNA? | protease |
| Eventually, what degrades RNase? | protease |
| in isolation of DNA of E. coli, how many mililiters of resuspended e. coli cells are in the tube in step 1? | 5ml |
| To break cell walls, we added 2 mls of what buffer? | EDTA |
| how many different bacteria were in the mixed culture in isolation by dilution? | 2 |
| How many bacteria were in the turbid broth in isolation by dilution? | 1 |
| In isolation by dilution...how do colonies on the surface of the pour plates differ from those suspended in agar? | because of different O2 requirements |
| what is a contaminate? | unwanted organism |
| how would you tell if a colony was contaminated on a streak plate? | it was in an area that was uninoculated and has different morphology |
| What would happen if plates were incubated a week longer? (ibd) | bacteria would be overgrown |
| What would happen if plates were incubated a month longer? | too numerous to count |
| How could your streak plate technique be improved? | 1)spread more evenly 2) flame and cool loop |
| Could some bacteria grow on the streak plate but not be seen using the pour plate? | depends on O2 requirements |
| what is a disadvantage of the streak plate | too many to count |
| what is a disadvantage of the pour plate? | hard to see isolation and solidifies too fast |
| What three organisms did we use in the oF-glucose test? | P. aeruginosa, E. coli, and A. faecalis |
| Why do most bacteria catabolize carbohydrates? | carbon and energy |
| What three sizes are carbohydrates classified as? | monosaccharide, disaccharide, and polysaccharide |
| How do we look for the presence of an exoenzyme? | by looking for a change in substrate outside of bacteria colony |
| What can enter a cell and be catabolized? | glucose |
| What are the metabolic endproducts of fermentation? | organic acids |
| What test helps determine whether an organism is oxidative or fermentative? | OF Glucose |
| What indictor does OF glucose use? | bromthymol blue |
| bromtymol blue turns what color in the presence of acids? | yellow |
Created by:
brimme123
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