MICROSCOPY
STAINING
PLATE TECHNIQUES
MISC
MEDIA
100

What magnification on a microscope should the oil immersion technique be used on?

100x

100

What is the difference between a differential stain and a simple stain?

Differential has 2+ dyes, Simple has 1

100

The streak plate technique is the single most important dilution method to accomplish __________.

The isolation of pure cultures

100

what is the difference between staphylococcus and streptococcus bacterial arrangements?

Streptococcus forms a linear plane, staphylococcus forms a cluster

100

What is the purpose of an indicator in agar?

Indicators change color based on pH or other specific metabolic products. These indicators make it very easy to identify different metabolic biochemistries by the naked eye.

200

What is the purpose of the condenser? 

To collect and direct light toward the slide

200

Why would we use a basic dye vs an acidic dye?

The dyes used in the simple staining process are basic dyes that contain positively charged chromophores (colored ions), which will be attracted to the negatively charged components on the cell’s membrane and wall. An acidic dye contains negatively charged ions that repel the bacterial cell and do not stain effectively.

200

How do you properly label a petri plate?

Use the Sharpie™ marker and label the bottom of the TSA plate with at least your initials & date, organism name(s), and the name of the medium. For easier viewing of microbial growth, label around the perimeter of the plate surface.

200

How does the Bunsen burner act as a type of aseptic technique? 

The flame creates a sterile field, as microbes and particles are forced upwards around the heat/flame.

200

MacConkey's agar will only grow bacteria that are __________.

Gram-Negative

300

How do you find the total magnification a compound microscope?

The total magnification of a compound microscope is determined by multiplying the magnifying power of the ocular lens by that of the objective lens used.

300

Why should young cultures (18 to 24 h) be used for staining?

Cultures that are older than 24 h may not take up the crystal violet/iodine complexes due to the deterioration of the peptidoglycan layer; these old cultures inappropriately appear gram negative.

300

What is the difference between the spread plate technique and the streak plate technique? 

Utensil, goal (growth vs isolation)

300

What are the two purposes of heat fixation?

Killing the bacteria, and adhering it to the slide

300

Mannitol Salt agar (MSA) is commonly used to differentiate among bacteria in the __________.

Staphylococcus genus

400

List 3 reasons why you may be unable to find any bacteria while looking through a microscope

Light isn't on/is not plugged in, microscope is not focused, lens is dirty/eroded, improper technique for staining, the stage keeps moving with focusing

400

Why is time an important factor in simple staining?

Time is important because it creates a contrast between the bacteria and the stain. If you over or under stain you won't be able to see bacteria.

400

How does smear preparation of cells from a liquid medium differ from the preparation of cells from an agar surface?

For agar surface colonies you need a drop or so of dH20
400

Give an example of bacterial colony: form, elevation, and margin (1 for each)

Form: punctiform, circular, filamentous, irregular, rhizoid, spindle

Elevation: Flat, raised, convex, pulvinate, umbonate

Margin: Entire, undulate. lobate, erase, filamentous, curled

400

If EMB agar shows bacterial growth in a green, metallic color what can you know about the bacteria growing?

Gram-negative fermenter

500

In microbiology, what is the most commonly used objective? Explain your answer.

Being able to view microscopic organisms.

500

List the steps for gram staining. Include regents and their purpose, timing and order. 

Answer is too long for text box to hold.

500
What would contribute to seeing bacterial growth results in Zone 1 & 2 but no results in Zones 3/4/5?

Killed bacteria with too hot of a loop, sample was too diluted, not long enough incubation time....

500

Define Bacteriostatic

Prevents the growth of bacteria (i.e., it keeps them in the stationary phase of growth)

500

is HE agar selective, differential or both? List all of the applicable selective, differential and or indicator components

The selective: bile salts

The differentiation: actose, sucrose, and salicin

 The indicators: Ferric ammonium citrate and sodium thiosulfate

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