MICR 2430 : Lab reports 1,3, and 5.docx

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redferret539

20 Nov 2014

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Selective media - designed to grow only specific bacteria but not others. eg. gn broth promotes the growth of gram negatives but not gram positive organisms. Differential media - designed to show the difference between different organisms grown on it. eg. some organisms look pink while others can look colourless on macconkey agar. Enriched media - designed to promote the growth of particular organisms. Different to selective in that it doesn"t usually specifically inhibit other growth. Step 2- place a drop of crystal violet solution on the smear and let sit for 1 minute. Then wash off the stain with a gentle stream of water. Step 3- add a drop of gram"s iodine solution and let sit for one minute. Step 4- add 2-3 drops of decolourizer, allowing it to run over the slide until no more dye is removed from the smear (no longer than 20s).

Related Questions

General Microbiology question.

If I gave you a broth mix of three bacteria; Bacterium 1 is agram-positive bacterium, Bacterium 2 is alactose-fermentation-positive negative bacterum and Bacterium 3 isa lactose-fermentation-negative gram-negative bacterium, what twoor three plates would you use to isolate them from one another anddistinguish them? Also, thoroughly describe what you would expecteach plate to contain/grow and what each growth might looklike.

I'm not really sure if this has anything to do with the questionabove, but during lab we used PEA (Phenyl Ethyl Alcohol), MSA(Mannitol Salt Agar), EMB (Eosin Methylene Blue) Agar, MacConkeyAgar, and Nutrient Agar.

eringerbil901

Microbiology

1) For gram positive cell walls, does the cell wall itself carry a negative charge and regulate movement of cations or is those characteristics of teichoic acid?

2) For basic dyes, it's a cation that stains a negatively charged microorganism?

3) Is the sole purpose for gram staining to differentiate between species?

4) Is carbolfuchsin a basic or acidic dye?

5) in special staining, do all tests (capsule, flagella, and endospore) show the halo effect?

6) in acid-fast staining, is there any interaction of charges?

7)the interaction between crystal violet and gram (-) bacteria. I assumed since gram (-) bacteria don't hold the dye, they do not interact. Can you explain how they do?

redfly628

If you were to make Columbia CNA with 5% sheep blood agar plates with twice as much colistin, how would the results likely be affected?

Select one:

a. Less Gram-positive growth, more Gram-negative growth

b. Less Gram-positive growth, no or even less Gram-negative growth

c. More Gram-positive growth, more Gram-negative growth

d. More Gram-positive growth, no or even less Gram-negative growth

e. Same Gram-positive growth, no or even less Gram-negative growth

In Mannitol Salt Agar lab, you were told to invert the plate before incubation. This is a common practice to avoid:

Select one:

a. Condensation drops

b. Increased smell

c. Decrease oxygen content

d. Bacteria from growing in wrong direction

e. Airborne contamination

If you see a yellow halo surrounding a colony on a MSA plate, which of the following is likely to be true?

Select one:

a. Glycolysis occurred

b. The organism is Staphylcoccus epidermidis

c. Colonies are not isolated

d. Fermentation occurred

e. Colony is Gram-negative

Which one of the following is found in MSA plates, but not in NA plates?

Select one:

a. Phenol red

b. Agar

c. Tryptose

d. Peptone

e. Beef extract

Why are the three organisms of Phenylethyl Alcohol Agar lab inoculated on the same plate?

Select one:

a. To avoid contamination

b. For easy viewing purposes.

c. To save resources

d. To avoid fluctuations in medium content and environmental effects.

For which reason would you most likely use a PEA plate for culturing after taking a sample from a patient?

Select one:

a. To isolate Streptococcus and Staphylococcus from other fecal bacteria.

b. To detect Escherichia contamination on the skin.

c. To find E. coli strains associated with food poisoning.

d. To identify gram-negative anaerobes in the patient's flora.

MICR 2430 : Lab reports 1,3, and 5.docx

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