Micro Lab Review Exam #1

UV radiation exposure will cause adjacent pyrimidines to form a covalent bond with one another which interferes with subsequent DNA replication and transcription. These are most commonly referred to as ________ dimers.

thymine-UV radiation exposure will cause adjacent thymines to form a covalent bond with one another which interferes with subsequent DNA replication and transcription. This pair of thymines is referred to as a thymine dimer or as a pyrimidine dimer.

The function of the nucleus is

to store genetic information.

Bacteria are _______, meaning that they are distributed everywhere.

ubiquitous

You are interested in studying the gram-negative bacteria that may be found in ground meat. You would like to use a medium that will enable the growth of most species of gram-negative bacteria, while inhibiting gram-positive bacteria. This would be a __________________ medium.

selective

A slide prepared with a simple staining technique is useful in determining ________. (Check all that apply.)

shape of individual cells arrangement of cells

Where should glass slides, pipettes, and capillary tubes be disposed?

sharps container

Cells which contain a thick layer of mycolic acid (cord factor)

Acid fast cells

You have successfully focused on an object with the 10x and 40x objective lenses. You have rotated the 100x objective lens into position but are unable to obtain a sharp image by rotating the fine focus adjustment knob. Which of the following is most likely to correct this problem?

Add a drop of immersion oil before rotating the 100x lens into position.

Objective lens system

After light passes through the specimen, it next enters this lens system

Who discovered one of the first antibiotics?

Alexander Fleming

Indicate which of the following observations can be made when observing growth on nutrient agar.

Amount of growth Opacity/clarity of colonies Color of colonies Shape and /or pattern of growth

What biosafety levels do most introductory microbiology students work with?

BSL-1

Please choose the answer that best completes the blanks of this sentence in the correct order. The ______ plate method involves spreading an inoculum onto the surface of a plate in a pattern that results in isolated colonies in some areas of the plate after incubation, whereas the ______ plate method involves diluting an inoculum into several melted agar tubes and then adding their contents into plates for solidification and incubation

streak; pour

Respirometers were set up that contained yeast and 2% glucose solution. Each respirometer was placed at a different temperature. The height of the bubble contained in the respirometer was measured every 5 minutes for 20 minutes. What is the independent variable in this experiment?

temperature

Endospores are less susceptible to UV damage because ________. (Check all that apply.)

the DNA of endospores is protected by small proteins that protect it from photochemical damage UV light generates a product in endospores that functions in the enzymatic repair of damaged DNA

The number of serial dilutions that are necessary for a standard plate count assay will depend on

the estimated density of cells in the original sample

Sanitization is a process by which

the microbial load on objects is reduced

When completing a quadrant streak, when do you flame the loop? (Check all that apply.)

Before you pick up a loopful of organisms from the original culture Before you streak quadrant two and three Before you return the loop to the receptacle

Order the reagents used in the acid-fast staining procedure.

Carbolfuchsin Acid-alcohol Methylene blue

Please select those nutritional requirements that are essential for growth, reproduction, and maintenance of a bacterial cell.

Carbon Hydrogen Nitrogen Oxygen Phosphorous Sulfur Vitamins and minerals Potassium Sodium Calcium Magnesium Chloride Iron

Adjustment knob

Causes stage (or objective lens) to move upward or downward

Which cellular structures were visible in the Elodea microscopy simulator?

Cell wall Central vacuole Chloroplasts

Condenser

Concentrates light onto the specimen

A culture which contains one or more unwanted and often unidentified microbes.

Contaminated culture

Which of the following items may be on the laboratory bench top while doing lab work? (Check all that apply)

Cultures (broth tubes, agar plates, agar slants) Equipment items specifically needed to complete the lab activity. Pencil or pen

_______ are marine algae that are responsible for "red tides" when great numbers of cells form blooms in the water.

Dinoflagellates

Which of the following are destroyed by alcohol?

Enveloped viruses Vegetative bacterial cells

After capsular staining, the cells are clear and the capsule is a dark purple ring.

False

All plant cells contain centrioles.

False

Beverages are allowed in the laboratory as long as the containers are covered.

False

For every bacterial cell that undergoes sporulation, there are two resulting bacterial cells.

False

Most chemicals used in the laboratory can be discarded in the sink after use.

False

Paper towels should be discarded in a biohazard container after washing hands.

False

The application of a disinfectant to the lab bench ensures that the work area is sterile before the laboratory exercise is started.

False

You may eat a snack in lab as long as there are no bacterial cultures on your bench and you have thoroughly washed your hands.

False

When testing an organism with several different antibiotics, the antibiotic that produces the largest zone is the one that the microorganism is most sensitive to.

False-Each antibiotic has different zone size interpretive criteria, and the zone size of each antibiotic must be checked against the standardized chart to determine whether the organism is sensitive, resistant, or intermediate to the antibiotic

The most versatile method of sterilizing heat-sensitive liquids is

Filtration

Arrange the following steps of applying immersion oil in the correct sequence.

Focus on the specimen using the 40x objective lens. Turn the objectives to half way between the 40x lens and the 100x lens. Apply a drop of immersion oil directly onto area of the slide you were viewing. Rotate the 100x lens over the microscope slide, and use the fine focus adjustment knob to sharpen the image.

Cells which contain both an inner and outer membrane as well as a thin layer of peptidoglycan

Gram negative cells

Cells which contain a thick layer of peptidoglycan and teichoic acid

Gram positive cells

Order these statements to indicate correct aseptic procedure for removing organisms from a culture for application to a slide.

Heat inoculating loop and wire to red-hot. Remove the cap of the culture tube and flame the mouth of the tube. Remove a loopful of organisms from the culture. Flame the mouth of the culture tube. Return the cap to the culture tube. Place organisms onto the slide in the center of the target circle. Flame the loop red-hot before setting aside.

Which bacterial genera will usually stain red during the acid-fast staining procedure?

Mycobacterium

Each of the following steps are necessary in preparing and observing a wet mount. Place the steps in the correct order.

Obtain a clean slide and cover slip. Using a transfer pipette, obtain a drop of specimen and place onto the center of the slide. Carefully place the cover slip over the drop of specimen. Observe preparation under the 10X objective lens. Observe preparation under the 40X objective lens.

Which function is associated with chloroplasts?

Photosynthesis

Stage

Platform that supports a microscope slide

Please choose the answer that best fills in the blanks of this sentence in the correct order. Gram-________ cells stain purple whereas gram-_______ cells stain pink or red when using the Gram stain technique.

Positive; Negative

The type of culture most frequently used in the laboratory which contains only a single species of microbe.

Pure culture

Which of the steps described here prevents the contamination of just-washed hands?

Use of a paper towel to turn off a faucet.

How is the bacteria inoculated on the MHA plate? (Picture not needed for answer)

Using a cotton swab to create a lawn

How does smear preparation of cells from a liquid medium differ from preparation of cells from a solid medium?

Water is applied to the slide before emulsifying cells from a solid medium.

A substance used to support the growth of microbial life is referred to as a ___________________________.

culture medium

The terms crateriform, umbonate, convex, flat, and raised are all used to describe the _______ of a colony.

elevation

Select all of the following that are products of alcoholic fermentation.

ethanol carbon dioxide ATP

Which of the following items should be autoclaved? (Check all that apply)

glass culture tubes biohazard bag

Which of the following substrates is fermented most easily by yeast?

glucose

Which of the following processes will occur in the presence or absence of oxygen?

glycolysis

A process common to all living organisms, whether aerobic or anaerobic, is

glycolysis.

Microorganisms that can grow at salt concentrations as high as 15 - 30% are known as:

halophiles

Which of the following solutions would be most likely to have the highest water concentration?

hypertonic solution

Which of the following are potential hazards which you might encounter in the laboratory? (Check all that apply)

infectious microorganisms open flames corrosive chemicals sharp tools or broken glass hot surfaces

An experiment involves the inoculation bacteria onto a variety of media with NaCl concentrations ranging from 1% to 25%. Which of these media is most likely to be isotonic with the bacterial cells?

1% NaCl

A total of 145 colonies were counted on the plate that received 1.0 mL of the 1:10,000 dilution of a specimen. What is the bacterial count for the original specimen?

1,450,000 colonies/mL

A total of 75 colonies were counted on the plate that received 1 mL of a diluted specimen. After calculating, it is determined that the total bacterial count in the original specimen was 75,000,000 colonies per mL. What was the dilution factor for the plated sample?

1:1,000,000

An experiment involves inoculating a variety of media with a NaCl concentration ranging from 1% to 25%. Which of these media would have the lowest water concentration?

25% NaCl

When performing a Standard Plate Count, plates that contain __________________ colonies are selected for counting with the Quebec Colony Counter.

30-300 colonies

If you wanted to prepare a 1:10,000 dilution of your sample and cannot measure out quantities of less than 1 mL, and have dilution blanks that can hold only 10 mL, how many dilution blanks will you need?

4

0.1 mL of an original sample is diluted into 9.9 mL of water and then 0.1 mL of this is spread on a plate. 54 colonies grew. What was the original cell density of the sample?

5.4 X 10^4 CFU/mL

You exposed this TSA plate to the air of the laboratory for 30 minutes, and then you incubated the plate for 24 hours at 37 degrees Celsius. What would be the correct quantitative evaluation of the degree of contamination on this plate?

50 to 100 colonies

Iris diaphram

Increases or decreases the light intensity

Place the steps of the Kirby-Bauer method of antimicrobial sensitivity testing in the correct order.

Isolate the microorganism to be tested in pure culture. Prepare a dilute suspension of the organism in nutrient broth to use as the inoculum. Using a swab, inoculate a Mueller-Hinton agar plate uniformly by swabbing in three directions. Dispense antibiotic disks onto the inoculated surface using sterile forceps or an automatic dispenser. Tap down disks with sterile forceps. Incubate for 16 - 18 hours at 37o C. Measure diameters of zones of inhibition and compare zone diameters to interpretive charts and determine if S, I, or R.

Indicate the way in which alcohol affects bacterial cells.

It coagulates proteins.

Which are advantages of the streak-plate method when compared to the pour-plate method?

It requires less materials. It is a very quick process.

What advantage does the pour-plate method have over the streak-plate method?

It requires less skill.

Jackie went to the sink at the end of lab to wash her hands. After removing her watch and rings, she turned on the water, wet her hands, added soap and thoroughly rubbed and lathered her hands for 30 seconds, cleaning the backs of her hands, her fingernails, and between her fingers. She then turned off the water, and reached for the paper towels to dry her hands. Identify the correct statement below.

Jackie should have used paper towels to turn off the faucet.

Place the following steps in order to demonstrate your understanding of the pour plate method.

Liquefy nutrient agar tubes and maintain at 50 degrees Celsius. Remove loopful of organisms from culture using aseptic technique. Add loopful of organisms to an agar tube. Transfer one loopful from one agar tube into another agar tube, and repeat this again with a third agar tube. Pour liquefied agar tubes into empty plates. Incubate for 24-48 hours.

Indicate the three most important considerations in maintaining a stock culture.

Maintaining the purity of the culture Preventing physiological or genetic changes to the culture Maximizing survival of the cells

The best source of information regarding the hazards posed by any chemical and specific handling instructions is the

Material Safety Data Sheet (MSDS)

A culture which contains two or more species which can be easily differentiated.

Mixed culture

Plasmolysis is the ________________ of a bacterial cell in a _____________ solution.

Shrinking.........Hypertonic

Which of the following terms are used to describe the appearance of the edge or margin of a colony growing on an agar surface?

Smooth Wavy Irregular

Indicate the correct order of steps for a broth to agar plate transfer.

Sterilize inoculating loop, remove cap of culture tube, and pass mouth of culture tube through the Bunsen burner flame. Remove a loopful of bacterial culture from the broth tube, pass the mouth of the tube through the Bunsen burner flame, and replace the cap. Lift the lid of the agar plate slightly and streak the loop across the surface of the agar plate. Replace lid. Sterilize inoculating loop prior to replacing in loop holder.

A second-level culture where an isolated colony from one culture is taken and transferred into a new medium.

Subculture

Please choose the development that led to the new three-domain system of classification.

The discovery of rRNA and its use in analyzing genetic relatedness

Why is the mouth of a culture tube passed through the Bunsen burner flame after removing and before replacing the cap?

To prevent the entry of ambient air which might introduce contaminants.

Most bacteria are smaller than most eukaryotic parasites.

True

Which of the following liquids can be safety pipetted by mouth? (Check all that apply)

You should never pipette anything by mouth.

When preparing a wet mount specimen for viewing, the specimen should be covered with

a coverslip.

Acetobacter aceti is a bacterial species involved in the production of acetic acid during vinegar production. Which category would this bacteria be classified within?

acidophile

All living things are made of _____.

cells

The __________ causes the stage to move upward or downward.

coarse adjustment knob

A ______ is a mound of cells on a solid medium that represents the progeny from one original bacterial cell.

colony

When determining the cell density of a sample by the standard plate count method, the final density of cells is reported as

colony forming units (CFU)/mL

Which of the following should be worn at ALL times in the lab? (Check all that apply)

lab coat closed-toed shoes protective goggles

Both human pathogens and normal microbiota are typically classified as:

mesophiles

Which of the following items should be disposed of in the sharps container? (Check all that apply)

needles glass pipettes broken glass scalpel blades

Which objective lens provides the highest total magnification?

oil immersion

Using oil immersion is useful because

oil immersion increases the resolving power of the specimen.

Lab coats, gloves, face masks, and goggles are all examples of

personal protective equipment

Which of the following is not a reaction that cells use to get energy from nutrients?

photosynthesis