Lab Final Flashcards

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1
Q

Define aseptic technique

A

method of handling microbes and material in a way that minimizes contamination

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2
Q

Define inoculation

A

process of transferring a microbe from 1 medium to the next

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3
Q

Define inoculum

A

sample being transferred

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4
Q

Which method is used to obtain pure culture

A

isolation streak plate . used to sperate individual bacteria. the concentration of bacteria is so low that a single bacterium or small group of cells comes off the loop to form single isolated colonies on the surface.

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5
Q

Why do we not heat fix negative stain slide

A

we want to see the shape and size of the microbes. Heat fix it changes the shape and size of the microbes.

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6
Q

In negative staining why do cells remain unstained and background is colored

A

the cells remained unstained because the dye we use ( nigrosin) is negative charged and the cell is negative charged so it repels the color and the background is colored instead

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7
Q

What is the advantage of negative staining

A

being able to visualize delicate structures and see shape and size better

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8
Q

How does negative staining work

A

Nigrosin and eosin.
Negative charged chromophore so because cell is negative charged. repel dye and dye can’t stain cell. so dye remains outside in the background

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9
Q

Gram Staining: What would you observe if you decolorized your slide too much? How would your cells appear?

A

cells may remove the dye from both gram + and - because it will denature the peptidoglycan so both will appear pink from safranin

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10
Q

Gram staining: you are looking at the smear of the mixture. All o the cells, cocci and bacilli, appear deep purple. What could have gone wrong

A

not have decolorized long enough. If you do not do it for 15-20 sec then it may not have weakened the outer membrane of gram - enough to release the dye.

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11
Q

Gram staining: Explain the relationship between the observed Gram reaction and bacterial cell wall structure

A

gram + stain purple because of the thick peptidoglycan layer that trap the dye in the wall. Gram - stain pink because of the thin peptidoglycan wall get denatured with the alcohol so it holds the counterstain safanin

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12
Q

Gram stain reagents

A

dyes/stain: crystal violent ( primary stain)

mordant: iodine. intensity color
decolorizer: acetone-alcohol ( solvent/denaturant)
counterstain: safranin

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13
Q

What are the steps of gram staining

A

1) water and comma size of microbe
2) air dry and heat fix
3) crystal violet 1 minute
4) wash with distill water
5) iodine for 1 minute
6) decolorize till color runs off
7) safranin 1 minute
8) rinse with distill water

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14
Q

What is the name of the stain prodedure used in endospore stain

A

Schaeffer-Fulton Methods

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15
Q

Steps in endospore staining

A

Primary Stain: malachite green
Counterstain: safranin

vegative cell wall appear red
endospore appear green

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16
Q

Endospore: You forgot to heat-fix your slide.What would you see?

A

you may not see anything or minimal microbes because we heat fix it to adhere to the microbes to the slide

17
Q

Endospores: List the reagents used in performing an endospore stain and describe their function

A

Primary Stain: malachite green. stain and penetrate spore coat
Distill water to remove excess stain
Safranin: counterstain that will stain and dye vegative cells wall red

18
Q

Endospore: How did the stained slide of 24-hour culture differ from the stained slide of the 1 week old culture

A

stained slide of 24 hrs culture has more vegative cells and very miminal endospores while the 1 week old had very little vegative cells and more endospores. This is due to the environment stress 1 week olf cultures went throught

19
Q

What is the function of blood agar

A

To see hemolysis type

20
Q

How does alpha hemolysis appear on the

A

partial lysis of rbc, leads to darkening of the blood agar . possible green color

21
Q

How does beta hemolysis appear

A

complete lysis of RBC and breakdown of hemoglobin ( colorless clearing of the blood agar)

22
Q

How does gamma hyolysis appear

A

no hemolysis so no change