Microbiology 202 Quiz 1 – Flashcards
113 test answers
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| What is the magnification of the eyepiece (ocular) of the microscope that we use in lab? |
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| 10x |
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| what are the 3 objective lens magnification? |
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| (4) 40x, (10) 100x, (45) 450x, (100) 1000x |
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| as the capacity to magnify _______, the diameter of the lens usually ________. |
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| increases, decreases |
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| what is done about the large about of light scattering at high magnifications? |
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| we use immersion oil! |
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| working distance |
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| distance between lens and specimen. |
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| working distance _______ with increasing magnification. |
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| decreases |
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| depth of field |
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| the distance between the highest point and the lowest point of a 3D object that is in sharp focus. |
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| depth of field _______ with increasing magnification. |
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| decreases |
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| at lower magnifications, the depth of field is ________. |
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| deeper. |
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| parfocal |
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| different lenses with different focal lengths are set in the rotating nose piece so that when you rotate them, the image should still be clear. |
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| iris diaphragm |
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| controls the amount of light passing through the slide....at a higher magnification the diameter of light is increased |
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| condenser |
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| focuses light coming up from the lamp below |
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| protozoan, fungal, plant, and animal cells are all what? |
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| eukaryotic cells |
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| difference between broths and agar? |
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| broths are liquid culture...agars are solidified. |
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| Frannie Hesse |
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| wife of Walther Hesse who created agar media |
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| agar will not melt until what temperature? |
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| 90 degrees |
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| turbid |
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| evenly suspended in solution to produce uniform cloudiness |
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| flocculent |
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| cells are floating in visible, separated clumps called floc |
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| pellicle |
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| cells form thick layer on the top of the broth, often due to high lipid content |
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| What is an appropriate storage temperature for 2-3 months? |
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| 0-4 degrees, refridgeration...good for anaerobes |
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| What is an appropriate storage temperature for long term? |
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| Freezing -20 to -100 degrees |
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| Lyophilizing |
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| freeze drying..removes H20 and cold to stop metabolism |
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| what can you do to ensure life during storage for facultative aerobes? |
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| stab tubes |
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| What is an appropriate storage temperature for 2-3 months? |
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| 0-4 degrees, refridgeration...good for anaerobes |
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| What is an appropriate storage temperature for long term? |
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| Freezing -20 to -100 degrees |
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| Lyophilizing |
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| freeze drying..removes H20 and cold to stop metabolism |
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| what can you do to ensure life during storage for facultative aerobes? |
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| stab tubes |
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| advantages of pour plating |
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| ..produces more isolated colonies |
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| disadvantages of pour plating |
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| more time consuming |
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| bacteriostasis |
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| cells are alive but inactive |
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| what is the best method of storage for strict aerobes? What about facultative anaerobes? |
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| refrigeration on agar slants--stab tubes. |
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| simple stain |
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| solely improves contrast with one stain |
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| differential stains |
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| Gram staining, acid fast stain |
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| structural stains |
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| spore and flagellum strains |
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| chromogen |
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| the colored ion in the simple stain |
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| chromophore |
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| part of a molecule that absorbs nd reflects particular wavelengths of light |
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| direct stains |
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| chromogen is positively charged |
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| indirect stains |
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| also called acid stains "negatively charged" |
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| pros of indirect staining |
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| not heated==> so there is no distortions...cells with want coatings reject the direct staining |
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| Eosin and Nigrosin are examples of what? |
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| indirect staining. |
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| which pH do direct and indirect stains work best at? |
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| direct: high indirect: low |
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| strepto |
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| arranged in chains |
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| staphylo |
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| cells that form clusters |
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| strepto |
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| arranged in chains |
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| staphylo |
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| cells that form clusters |
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| what do gram positive cells have that gram negative cells do not have? |
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| thick peptidoglycan wall |
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| what do gram negative bacteria have on the outside of their cells? |
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| phospholipid envelope and small peptidoglycan layer |
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| when stained, gram positive cells are _______ in color. |
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| purple |
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| when stained, gram negative cells are _______ in color. |
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| pink/red |
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| what can lead to the decolorization of crystal violet from gram positive cells ? |
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| over-colorization, age of the cells, acidity of the media. Media pH drops in time, so you should do it right away. |
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| The spore stain is an example of what kind of stain? |
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| structural |
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| Which bacteria is known for causing food poisoning? How do they do that? |
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| B. cereus--> they produce enterotoxins |
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| Which bacteria are STRICT anaerobes and are soil dwellers? |
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| clostridium |
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| Which bacteria causes botulism--when seeds germinate under anaerobic condition? |
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| C. botulinum |
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| Which bacteria can cause wound infection by gas gangrene and cause food poisoning/? |
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| C. perfringens |
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| Which step comes first in the process of spore staining? Decolorizer or Counterstain? |
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| decolorizer |
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| What does glucose satisfy? |
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| chemical energy and carbon source |
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| what are peptones and tryptones examples of? |
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| protein digests that have amino acids |
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| Complex media |
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| if any of the said ingredients are undefined, then it is complex. |
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| Minimal agar is what type of media? |
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| defined media |
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| How does autoclave raise the temperatures so high? |
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| raising PSI until 15-20 and the temperature increases to 250 F. |
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| Ionizing Radiation |
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| strip electrons from atoms, mutates DNA, and used to sterilize food and some plastic wear. |
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| Filtration |
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| removes pathogens from air; used in place of autoclaving if something is heat sensitive. |
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| Which type of sterilization method is used to sterilize biohazard bags? |
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| bunsen burner and large scale incineration |
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| ethylene oxide, |
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| sterilizing gas to clean moisture sensitive equipment |
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| psychrophiles |
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| cold loving microbes from -5 to 20 C. ..found in alpine and arctic soils |
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| psychotrophs |
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| 20 -30degrees |
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| mesophiles |
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| 25- 40degrees |
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| thermophiles |
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| 55 to 65 |
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| hyperthermophiles |
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| most have optional temperatures at 25-35, but can withstand temperatures above 100 for more than 10 minutes |
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| hypotonic environments |
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| expanding cell due to higher concentration inside cell |
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| hypertonic environments |
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| water flows out of the cell because there is more solute on the outside of the cell |
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| exoenzymes |
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| enzymes that act on substrates on the outside of the cells. |
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| If you wanted to find a bacteria that produced exoenzymes, where would you look ? |
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| the soil |
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| what's the difference between amylopectin and amylose? |
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| amylose is tightly bound glucose molecules starch while amylopectin is loosely bound branching chains of glucose |
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| What do amylases do? |
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| they are enzymes that are secreted from the cell that break down large poylmers of starch and transport them across the cell |
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| how can you tell if the cells produce amylase? |
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| if there is a colorless zone or halo extending out from the microbial growth surrounded by the areas stained by blue-violet, this is a positive reaction. |
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| what is the purpose of the phenol red carbohydrates assays? |
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| used to asses a given microorganism's ability to produce the intracellular enzymes needed to ferment mono-disaccharides. Does this through tracking pH changes |
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| using phenol red, from 5.3-6.3, the color of the liquid is ________? |
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| yellow |
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| using phenol red, from 6.8-7.8, the color of the liquid is ________? |
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| orange |
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| using phenol red, from 8.3 to 9.3, the color of the liquid is ________? |
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| red |
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| what is a positive reaction for the test of fermentation? |
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| broth has bright yellow color |
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| what is a negative reaction for the test of fermentation? |
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| orange to red color |
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| What is an example of a false negative in the fermentation assay? |
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| false negative can occur if the bacteria exhausted the supply of sugars by rapid fermentation, and then used amino acids as the primary source. This would generate NH3 and would raise the pH. |
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| What is the casein assay testing for? |
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| secreted proteases |
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| what is the positive result for the casein reaction? |
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| if there is a transparent zone, then proteases were secreted! |
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| what does the lysine debaroxylase assay test? |
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| production of cadaverine and/CO2..detects removal of carboxyl group from lysine |
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| why is bromocresolpurple used instead of phenol red for the lysine decarboxylase assay? |
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| it changes at a lower pH(more acidic) |
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| what is the positive assay result for lysine decarboxylase ? |
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| purple color |
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| what is the negative assay result for lysine decarboxylase ? |
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| yellow color |
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| Why can't see view viruses in this lab? |
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| Because our microscopes only reach to .4 and .7um and cannot magnify or resolve to a typical virus size of .01 and .10. |
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| What is the relationship between resolution and wavelength? |
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| r = (1/2) lambda |
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| What is the difference between "high resolution" and " high magnification" |
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| high resolution- the distance between two objects that reveals them as separate objects is minimized. high magnification - the enlargement of the specimen when seen through the microscope is maximized. |
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| Besides using immersion oil, what makes using the 1000x magnification difficult? |
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| 1. depth of field is too shallow 2. shorter working distance |
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| What color is S. morescans? |
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| red |
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| What two things could you do if your streak plating failed? |
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| 1. pour plating 2. wait longer for the sterile loop to cool |
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| Is E. coli gram positive or negative? |
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| negative |
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| Is M. luteus gram positive or negative? Strucutre? |
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| positive, tetrad, coccus |
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| Is B. megatherium gram positive or negative? What is its structure? |
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| positive, strepto, chains |
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| This bacteria is diplo and cocci |
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| e. coli |
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| What is the gram stain and structure of E. faecalis? |
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| gram positive, streptobaccilus |
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| Why are gram positive cells purple? |
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| they retain the purple color of crystal violet better in their peptidoglycan layer |
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| When B. megatherium cells are gram stained, the cells may have white colorless oval inside the cells. What are these ovals and why are they colorless? |
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| these parts are cell parts that were metabolically active before staining. They are colorless because the staining will lose its malachite green when rinsed with water. |
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| You do a gram stain of M. luteus, but see that there are cells present that are both purple and red. Explain what you see. |
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| Because M. luteus is gram positive, you couldv'e stained with safranin for too long or destained too much |
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| You do a gram stain with E. coli and see that half the cells are purple and half the cells are red. Explain what you see. |
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| Because E. coli is gram negative, you didn't destain enough |
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| At higher magnifications, the light intensity dial should be adjusted that the lamp produces ________ light. |
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| MORE |
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| We will mostly work with what type of bacteria? |
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| chemohetertrophic...we must provide carbon source |
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| What are some precautionary steps you should take when using an autoclave? |
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| use slow exhaust setting when autoclaving liquids, make sure it reads 0 psi before opening the door, stand back, do not swirl test tubes and beakers |
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| hyperthermophiles |
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| 75 to 90 |
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