Valencia College Microbiology Lab Exam 1

Magnification is achieved in a light microscope through the initial magnification of the specimen by the _____ lens.

This image is then projected to the ____ lens that will further magnify the specimen to form a virtual image received by the eye.

objective; ocular

Illuminator is also called ______.

Light source

What is the magnification of the ocular lens?

10x

Total magnification of the specimen being viewed with the scanning power objective would be ____.

40x

All of the following are diameters of cells that would be resolved in a microscope with a limit of resolution of 0.2 micrometers except _____.

0.1 micrometers

To finally view a specimen under the 40x, with which objective lens should you begin?

4x

A microscope’s _____ helps distinguish between two close objects so as to provide a clear image.

Resolution

Which of the following is used for precise focusing?

Fine adjustment knob

With which object lens/lenses should you use the coarse adjustment knob on the microscope? (the one that raises and lowers the stage)

4x

With which objective lens/lenses should you use the fine adjustment knob? (the one used for focusing)

all of them

The purpose of staining the specimens on the microscope slides is to increase the ____ of the viewed object.

contrast

True or False: The condenser is a glass lens which is used to focus the light onto the specimen and not to magnify the specimen.

True

What is the alternative name for a 100x objective lens?

oil immersion lens

True or False: Magnification of the condenser lens is 10x.

False

If a size of a bacterial cell you are viewing under the microscope is 10 micrometer, how would you express it in millimeters?

0.01 mm

Identify three pieces of protective attire used in the microbiology lab.

lab coat, gloves, goggles

True or False: immediately following a bacterial spill, you should cover the area with paper towels, saturate the paper towels with ethyl alcohol and leave the paper towels for at least 20 seconds to fully kill the microbes.

False

25 C is occasionally used as an incubation temperature for pathogens as it corresponds to _____ temperature.

room

37 C is a more commonly used incubation temperature for most pathogens as it corresponds to ____ temperature.

body

Where do you place gloves and contaminated petri dishes when disposing of them?

biohazard bin

What one procedure, according to the CDC, is essential in order to prevent the spread of infections to patients?

washing hands

Before turning your microscopes off, you must remember to adjust the ____ to its lowest setting so that the next student who turns it on does not accidentally have the bulb blown out.

rheostat

In what orientation/position should all petri dishes be stored and incubated once media has been allowed to solidify within them?

inverted

Any culture that contains two or more species of microbes is referred to as a(n) ______ culture.

mixed

A culture that contains only a single species of microbe is referred to as a ___ culture.

pure

The purpose of performing a quadrant streak plate on agar media is to ____ a single species of microbe from a mixed culture through the use of friction.

isolate

Failure to use iodine during the gram staining procedure would have the greatest impact on properly identifying gram-____ cells.

positive

The counterstain that is used in both the Gram stain and the endospore stain is ____.

safranin

During the spore training procedure, _____ is the mordant that is applied to the slide along with malachite green dye.

(mordant - a substance that fixes or enhances the binding of a dye to a specimen)

heat

You suspect that a patient might have a Mycobacterium tuberculosis infection. As a result, you order a(n) ________ staining technique to confirm your suspicions since you know that Mycobacterium tuberculosis contains ______ in its cell wall.

acid-fast; mycolic acid

Phenylethyl alcohol agar (PEA) is an excellent way to isolate Gram-_____ bacteria because it is a selectable medium that favors their growth and inhibits the growth of Gram-_____ bacteria through the addition of phenylethyl alcohol.

positive; negative

To select for the growth of Staphylococcus sp. on mannitol salt agar (MSA), the media contains _____. If the organism is Staphylococcus aureus, then the media will turn the color _____ yellow, since that is the one species of Staphylococcus that can ferment ______.

7.5% NaCl; yellow; mannitol

______ is the indicator for lactose fermentation in MacConkey agar media as it changes from colorless to ______ in the presence of acids (acids are the byproduct of lactose fermentation).

neutral red; hot pink

Columbia CNA with 5% Sheep Blood Agar is not only a selective media because of the addition of antibiotics, but also a differential media because the presence of blood can be used to identify different types of ______ G+ bacteria based on the degree of blood degredation.

hemolytic

Alpha hemolysis

incomplete/partial hemolysis

Beta hemolysis

complete hemolysis

Gamma hemolysis

no hemolysis

Colonies of Salmonella sp. are easy to identify on Hektoen Enteric Agar because they turn _____ as a result of the production of H2S by these organisms, however they will never cause the media to turn the color _____ because they cannot ferment disaccharides.

black; orange

What type of media is Eosin Methylene Blue (EMB)?

Differential media AND selective media

What role do colistin and nalidixic acid play in the Columbia CNA blood agar?

Selective agents

Aerotolerance refers to the ability or inability to survive in the presence of _____.

oxygen

Casein, not lactose, is the predominant protein in ______ and it is catabolized by the enzyme ______.

milk; casease

The enzyme alpha-amylase is one of the two enzymes responsible for the breakdown of _______.

starch

_______ are enzymes that catabolize triglycerides into their individual glycerol and fatty acid components.

lipases

_______ is an important addition to FTM as it eliminates O2 by converting it into H2O, while _____ identifies the limit of O2 diffusion into the medium by turning into the color pink when oxidized.

Thioglycollate; resazurin

General location of where you would find an obligate anaerobe in FTM medium and why it would be there.

anoxic/anaerobic zone because it cannot defend against free radical oxygen molecules nor can it utilize oxygen

General location of where you would find an obligate aerobe in FTM medium and why it would be there.

oxic/aerobic zone because it can utilize oxygen and defend against it

General location of where you would find an facultative anaerobe in FTM medium and why it would be there.

all throughout because they can produce enzymes to defend against ROS (reactive oxygen species).

Organisms such as E. coli and S. marcesescenes, with an optimum temperature within the range of human body temperature are most appropriately termed ____.

mesophiles

After incubating a microbe at 5C, 25C, 37C, and 60C, you notice that the broths incubated at 25 and 37C have growth, while all the others do not. Based on these results, what kind of organism is this with respect to temperature requirements?

mesophile

After incubating a microbe at 5C, 25C, 37C, and 60C, you notice that the broths incubated at 5 and 25C have growth, while all the others do not. Based on these results, what kind of organism is this with respect to temperature requirements?

psychrotroph

When comparing a psychrophile and a psychrotroph, which one is more likely to cause potential health issues for a human host?

psychrotroph

One type of microbe has a range of -15C to 15C, which one is it?

Psychrophile

In order to identify the location of the starch on a starch agar plate, it is important to first add the indicator _____, at which point the starch will turn the color ____.

iodine; brown

A zone of clearing around a colony on a starch agar plate after the addition of the indicator indicates the production of the enzyme _____ by the bacteria.

amylase

Enzymes that hydrolyze triglycerides into their corresponding fatty acids and glycerol are generically referred to as ____.

lipases

The fatty acid byproducts of lipid metabolism can be converted to acetyl-CoA through a process known as ______.

Beta-oxidation

A zone of clearing on milk agar plate indicates the production of the enzyme ______ by the microbe and indicates that the organism has metabolized the protein _____.

casease; casein

To test for the presence of catalase within a microbe, you must first add the reagent _______.

hydrogen peroxide

If the microbe does produce catalase, the hydrogen peroxide will begin to _____, verifying the presence of the enzyme. The cause of this is the byproduct _____.

bubble; oxygen

What are the two byproducts of a catalase reaction that breaks down hydrogen peroxide (H2O2)?

Hydrogen and Oxygen

If an organism has cytochrome c oxidase within its cell, it must also possess a(n) _________ used during cellular respiration

electron transport chain

What is the specific visual confirmation (on a cotton swab) of the presence of cytochrome c oxidase within an organism after the addition of the chromogenic reducing agent?

blue color

The ______ is the term used for the accumulation of bacteria that is collected from the culture tubes and then moved into a new medium in order to produce a culture. 

inoculation

Method used to inoculate broth media

dip and swirl

method used to inoculate slant media

fish tail

method used to inoculate deep media

stab

What is the purpose of the agar added to certain media

to solidify the media (and provide a solid surface for cultures to grow on)

To decrease the likelihood of contamination, how should you hold your agar plates when working with them?

vertically

In order for the autoclave to achieve maximum sterility, it is important to achieve a temperature of _____ and a pressure of ______ for about 30 minutes.

121 C, 15 psi

Basic dyes are used to perform simple and differential staining techniques because they employ a ______-charged chromogen that is electrostatically attracted to the _____ bacterial surface.

positive; negative

Provide two examples of basic dyes commonly used in the lab:

(note: these are BASIC dyes, meaning they are positively charged. Unlike acidic/ACID dyes, which are negatively charged)

crystal violet, safranin pink, and methylene blue

A ______ stain is typically used to identify the true shapes of cells because the nigrosin will not bind to the cell and will color the background.

(note: nigrosin is an acidic dye)

negative

Before viewing your specimen with the 100x lens, _____ must first be added to the slide to prevent light from refracting and not entering the lens.

immersion oil

Prior to heat-fixing your specimen to the slide, it is crucial that you first allow plenty of time for the smear to completely ____ dry

air

Why does the process of heat-fixing your slide allow your specimen to adhere to the slide better than if this step is omitted?

proteins (peptidoglycan) stick to the slide (through coagulation) after being denatured by heat

When placing your scopes away at the end of lab, you should ensure that the ____ objective lens is directly over the stage and that the ______ is turned all the way down to prevent damage to the bulb when turned on again.

scanning; rheostat

What is the function of a mordant when performing various differential stain techniques?

Fixes the primary stain to the cell

What is the mordant used in the Gram staining technique?

iodine

(creates a crystal violet-iodine complex that binds to cells)

When the Gram staining technique is performed correctly, bacteria that stain purple with the crystal violet are classified as Gram-____.

positive

After the addition of the 95% alcohol, all of the bacteria that are considered to be Gram-_____ will be colorless, until the counterstain is applied.

negative

The ____ differential staining technique is useful in identifying bacteria possessing mycolic acid (wax) in their cell walls. A clinically important genus of bacteria that has mycolic acid in its cell walls is ______.

(note: mycolic acid is a key word for the genus)

acid-fast; mycobacterium

Clostridium and Bacillus are both clinically important genera of bacteria that produce _____, tough structures used to protect their DNA during times of environmental stress.

endospores

A _____ media contains inhibitory agents that prevent or significantly reduce the growth of certain kinds of bacteria.

selective