BIO 206 Lab Exam 1 - PRACTICE QUESTIONS

Students will receive a safety violation for all of the following EXCEPT:

Wearing open-toed shoes and/or shorts

 

Getting out your phone or electronic device one or two steps before exiting the lab room

 

Borrowing goggles from media prep

 

Wearing a loose hat in lab

 

Getting out your phone or electronic device one or two steps after exiting the lab room

 

Not completing the safety agreement by the due date

 

Storing a water bottle in the side pocket of a backpack where it is visible

 

Putting gloves in the regular trash can

 

Throwing away food or drink trash in the lab trash can

 

Getting out your phone or electronic device one or two steps after exiting the lab room

Microorganims are ubiquitous. This means they would be found in which of the following places? 

Soil 

The body

On an aluminum railing

a and b

All of the above

all of the above

Some bacteria can lyse (break down) red blood cells in a process called hemolysis. Match the following descriptions of hemolysis with the correct outcome on a blood agar plate:

a hemolysis

b hemolysis

y hemolysis

• The blood agar plate will show clear around the bacterial growth due to complete hemolysis of the red blood cells

• the blood agar plate will show no hemolysis

• there will be a greenish colored zone around the bacterial growth due to incomplete lysis of the red blood cells

a hemolysis: there will be a greenish colored zone around the bacterial growth due to incomplete lysis of the red blood cells

b hemolysis: The blood agar plate will show clear around the bacterial growth due to complete hemolysis of the red blood cells

y hemolysis: there will be a greenish colored zone around the bacterial growth due to incomplete lysis of the red blood cells

Where would you expect to find a saprophyte organism? 

in soil

Which of the following morphology terms would describe a tiny pinpoint colony?

punctiform

Match the media type below with its intended purpose?

plates

agar slants

broths

• used to grow cultures

• used when you want to grow a culture to store in the refrigerator

• used to isolate species

plates: used to isolate species

agar slants: used when you want to grow a culture to store in the refrigerator

broths: used to grow cultures

The purpose of the streak plate method is to isolate individual colonies. Which of the following things is NOT true about the streak plate method? 

 

Your most isolated colonies should appear in quadrant 1

How often should you sterilize your loop when doing a streak plate?

 

At the beginning, every time you change quadrants, and at the end

Which of the following things is a safe practice when transferring cultures?

 

Hold the inoculating loop like a pencil

The handles of inoculating loops can get very hot.  How hot can your inoculating loop get if you leave it in the incinerator for a really long time?

 

close to 800*

When a cap is removed from a tube in the transfer process, where does that cap go?

 

It is held by the pinky finger of your loop hand

What is the appropriate time to flame your inoculating loop when transferring your culture

 

Both before and after you transfer the bacteria

Which of the following is the correct location to label a tube and a plate?

 

Tubes are labeled on the glass and plates are labeled on the bottom

Which of the following things below would result in a pure culture?  

 

A completely isolated colony growing on a plate

In your epi-tubes you are transferring continually more dilute samples from tube to tube. According to your spread plate protocol, which of the following represents the order of tubes from most concentrated to most dilute?

 

Tube order: A,B,C,D

What does CFU stand for?

 

Colony forming units

What does the Kirby-Bauer method test for?

 

It tests for how well an antibiotic works against a particular organism

Which of the following statements about antibiotic resistance testing is true?

 

If you say a bacteria is susceptible to an antibiotic it means that the antibiotic can kill it.

In order to get agglutination (clumping) in a blood typing experiment, an antibody would have to bind to its appropriate glycosylated protein on the blood cell. The antibodies in this experiment are called Antiserum, and they give the label of the protein they react with.  This means that if you have A type blood, it should react with the following antiserum (antibody solution).

 

Anti A antiserum

Although it is best to get an exact match to your blood type, there is a universal donor who can potentially give blood to anyone. Which of the following would be the universal donor?

 

Type O blood

True or False; When doing a bacteriophage sensitivity plate, you streak the phage on the plate FIRST, and the bacterial strain second.

True

There is only ONE objective you should use when using lens immersion oil. The oil will damage all other objectives. According to figure 3.4, how would you identify the only lens in which you would use immersion oil?

 

It has a black and white ring around it

How would you calculate the total magnification of a microscope?

 

You multiply the magnification of the Ocular lens by the magnification of the Objective lens

What would you use to clean lens immersion oil off of your objective lens before putting your microscope away?

 

Special lens paper

What kind of microscope will you be using in this laboratory exercise?

 

A light microscope

Which of the following is the reason a simple stain will stick to a bacteria?

 

They are positively charged and the bacteria are negatively charged

How much water would you use on a slide when doing a bacterial smear procedure?

 

A very small amount

Which of the following explanations is correct as to how a negative stain works?

 

They are negatively charged and therefore are repelled by the bacteria, and surround it so that it stands out.

Under which circumstances would you choose a negative stain protocol over a Gram stain?

 

If the bacteria would lose their delicate shape or shrink when heat fixing

What is the correct term for a chemical that helps to fix another chemical in place by complexing with it?

mordant

After which of the following steps in the Gram stain process could you detect a difference between Gram + and Gram- bacteria if you looked really hard?

 

After de-colorization with alcohol

Which of the following is NOT a source of getting a poor/ inconsistent Gram stain?

 

Making sure to air dry the smear before heat fixing

What would you call a media that allows two different organisms to grow on it, but their biochemical properties allowed you to see a physical difference between the two?

 

Differential media

What is the most frequent thing you would be checking on the majority of the biochemical tests?

 

For a change in pH/ acid-base

In the oxidase test, if you see no color change within 20 seconds but then see a color change to blue after two minutes has passed, how will you interpret this result?  

Negative

What is the primary purpose of streaking for individual colonies?

to decrease cell density, and to obtain isolated colonies

When using the streak plate technique how often is it necessary to sterilize your loop? 

 

Before you obtain culture on your loop

 

Between quadrants on your streak plate

 

After you have completed the last quadrant

What could be a possible explanation for what went wrong on the streak plate below?

The loop was not sterilized between quadrants

What criteria must be met for a culture to be considered a pure culture?

A culture that contains a single bacterial species

What results would you see for the following streak plate technique errors?  Answers can be used more than once.

Obtaining a culture sample before streaking every quadrant.

Not sterilizing the loop between each quadrant

Not drawing your loop through the previous quadrant

Sterilizing your loop after obtaining a culture sample but before streaking your plate

No single colonies, all four quadrants look the same

Growth only in quadrant 1

No growth on the plate

Obtaining a culture sample before streaking every quadrant. No single colonies, all four quadrants look the same

Not sterilizing the loop between each quadrant. No single colonies, all four quadrants look the same

Not drawing your loop through the previous quadrant. Growth only in quadrant 1

Sterilizing your loop after obtaining a culture sample but before streaking your plate. No growth on the plate.

If you take 100 µL of a sample and add it to 9.9 mL of saline, what is the dilution of the new solution?

 

10^-2

After performing a spread plate, you count 110 colonies on your plate that has a dilution factor of 10^-4. You know you plated 100 µL of your sample on the plate. What is the CFU/mL of the original undiluted sample?

 

1.1 x 10⁷ CFU/mL

Your lab procedure involves transferring liquids with the following volumes: 10 µL, 75 µL, and 120 µL. Which micropipette(s) would you use for this experiment?

 

P20 and P200

You are performing serial dilutions of a bacterial culture for your experiment. On the first dilution you need to transfer 200 uL from the undiluted culture to 1800 uL TSB. From there on, you will transfer 10 uL from the previous dilution into 990 uL TSB 2 consecutive times.

What is the final dilution you will obtain from the original culture?

10^-5

You want to know the concentration of an E. coli culture tube for an experiment. For this purpose, you dilute the original culture to 10^-7 and plate 100uL of each dilution on TSA plates. After 24h of incubation you count 137 CFU on the 10^-6 dilution plate.

Calculate the CFU/mL of the original culture tube.

1.37 x 10⁹

The Antibiotic Susceptibility results for E. coli using Tetracycline, Neomycin, and Erythromycin are shown below.  Which of these is E. coli susceptible to?  The antibiotic inhibition chart can be found in the weekly powerpoint.

Tetracycline, 20 mm

What is the difference between bactericidal and bacteriostatic?

Bactericidal agents kill the microbe

Would you expect Gram-positive bacteria or Gram negative bacteria to be more susceptible to antibiotics? Why?

Gram-positive bacteria are more susceptible due to their lack of an outer lipid membrane

What is the purpose of heat fixing?

• to adhere bacterial cells to the slide

• to kill the bacterial cells

What is the benefit of using a differential stain versus a simple or negative stain?

they all a microbiology to determine differences between organisms or between parts of the same organisms

why may a gram stain not yield clear results?

• poor technique while performing gram stain

• the age of the culture

• the emulsion is too thick

list the steps of the gram stain procedure in the proper order.

• prepare an emulsion of bacteria

• heat fix

• saturate w crystal violet

• rinse w distilled water

• saturate w iodine

• rinse w water

• rinse w alcohol until runoff is clear

• rinse w water

• saturate w safranin

• rinse w water

• dry w bibulous paper

predict effect of failing to add iodine to gram-positive cells

the cells will appear red/pink

predict the effect of failing to apply decolorizer

cells will appear purple

predict effect of failure to apply safranin

appear purple or colorless

predict the effect of reversal of crystal violet and safrinin stain

cells appear purple

what is the purpose of the mordant when Gram staining?

to enhance crystal violet staining by forming a crystal violet-iodine complex

youre expecting gram-positive bacilli and red/pink gram-negattive cocci. you observe purple bacilli and purple cocci. how do you explain this?

sample was under-decolorized