Micro Lab Final Exam

Why is it important to center an object you are analyzing in the field of view of the microscope before switching to a higher power lens?

As magnification increases, field diameter decreases and objects at the periphery will no longer be in the visible field

Which of the following is a common reason to inoculate a culture onto a slant rather than into a broth?

Because you intend to store the culture as a stock culture in the refrigerator for several weeks.

Most microscopes are parfocal. This means that the distance from the nosepiece opening to the focal plane of each lens has been standardized. What does this mean to you with regard to how you use the microscope?

Once the specimen is in focus under a low power lens, the microscope can be switched to a higher power lens without moving the stage and the image will be in or nearly in focus no matter what lens is used

Although easier to prepare, why might a standard wet mount not provide good results for observing motility?

Placing the cover glass directly on a flat slide provides very little space in which the cells can move.

In the acid-fast procedure, why is the sample counterstained with methylene blue or brilliant green rather than safranin which is used as the counterstain in the Gram stain procedure?

Safranin is pink like carbolfuchsin and would not allow one to differentiate between the cell types.

Where would you dispose of a broken slide which might have live bacterial culture on it?

Sharps box

What do you predict would happen if you mistakenly added only 1.5 grams of agar instead of the 15 grams the Nutrient Agar recipe calls for?

The agar media would either be very soft or possibly remain liquid.

What is the function of the petroleum jelly in the preparation of a hanging drop slide?

To adhere the cover glass to the slide with an air-tight seal.

During the simple stain procedure, why is it necessary to heat fix the cells?

To adhere them to the slide.

Why is the magnetic stir bar added to the flask prior to autoclaving, for a stirring step that occurs with the sterile media later, right before the plates and tubes are to be poured?

To avoid introducing contamination after the media has been sterilized.

Why is it advisable to close doors and turn off fans while preparing bacterial growth media?

To minimize airborne contamination of the media.

How does true motility differ in appearance from Brownian motion?

With motility, cells will each exhibit independent movement over greater distances.

A leukocyte that is about twice the size of an erythrocyte and displays a multi-lobed nucleus and pale purple cytoplasmic granules in a stained blood smear is

a neutrophil.

The capsule stain involves the use of both

acidic stain and negative stain.

Chromogens that function as basic stains in the simple staining procedure color the bacterial cell by

adhering to the negatively charged cell.

. If you failed to perform the decolorization step during the acid-fast staining procedure

all the cells would appear pink.

A leukocyte that is about twice the size of an erythrocyte and displays a bi-lobed nucleus and red-pink cytoplasmic granules in a stained blood smear is

an eosinophil.

The least abundant type of leukocyte in a normal blood sample is the

basophil.

Basic growth media must be formulated to meet the diverse nutritional requirements of routinely cultivated bacteria, which includes supplying sources of ____________ and nitrogen in various forms.

carbon

If the total magnification of a microscope can be increased by simply adding more lenses, why are bright-field light microscopes not outfitted to magnify things greater than 1300X?

cause the resolution limit for a light microscope is about 0.2um, magnifications above this will not produce clear images

Undefined, or complex media has a recipe that is

formulated from the digests of plant or animal material.

Upon competition of the endospore staining procedure, the endospore will appear

green

Differential stains function to

highlight differences between cells or parts of a cell.

Organisms that are able to grow in boiling geothermal pools would be called

hyperthermophiles

Human pathogens are

mesophiles

The most abundant type of leukocyte in a normal blood sample is the

neutrophil.

Wet mount preparations of bacteria are more difficult to see under the microscope than a Gram stained slide because the cells are

not stained to contrast with the slide

The capsule of a bacterial cell is located

outside the wall.

Upon completion of the Gram stain, Gram-positive cells will appear

purple.

The cardinal temperatures describe the

range of temperatures that allow growth and survival of an organism.

The term coccus describes a bacterial shape that is

spherical

In the Gram stain procedure, the primary stain crystal violet functions to

stain all bacterial cell walls.

An organism with an optimal growth temperature around 65°C would be called a

thermophile.

Endospores are produced by bacteria

to survive poor environmental conditions.

Upon completion of the capsule staining procedure, the capsule will appear

unstained.

Fluorescent microscopy differs from other types of light microscopy in that it requires

use of an ultraviolet light source.

Aseptic technique means that that you perform the preparation of media or the transfer of living microbes

without introducing contamination.