Microbiology Lab Questions. Question 1

You are reading culture plates today and identifying pathogens that grow from patient samples.

Which two pieces of information are absolutely critical in determining which additional tests must be done to identify the pathogen?

a) Appearance on charcoal agar

b) Endospore Stain

c) Gram Stain

d) Oxygen sensitivity

Question 2

A 10 year old has a wound on the arm that the physician suspects is infected.

Upon culture, you see small white colonies growing on blood agar as well as chocolate agar.

You gram stain the colonies to find that they are gram positive cocci.

Which test will you perform first?

a) catalase

b) indole

c) lactose fermentation

d) coagulase

Question 3

You have isolated catalase positive gram positive cocci from a wound culture.

Which test will you perform next?

a) coagulase

b) P disc, containing optichin

c) A disc, containing bacitracin

Question 4

You are working on a sputum culture.

You see mucoid alpha hemolytic colonies that number many more than the normal flora present.

The gram stain of the colonies shows gram positive cocci that are in lancet shaped pairs.

Which test will you do?

a) P disc, containing optichin

b) A disc, containing bacitracin

c) motility

d) acid fast staining

Question 5

You are working up a throat culture.

Standard procedure in plating throat cultures in your lab includes dropping an A disc near the initial inoculum in the first quandrant when streaking the specimen.

You examine the blood agar plate and see moderate normal flora and many beta hemolytic colonies that do not grow up to the A disc.

The beta hemolytic colonies are catalase negative gram positive cocci.

Which pathogen is in this throat culture?

a)Streptococcus agalactiae

b) Staphylococcus aureus

c) Streptococcus pyogenes

d) Staphylococcus epidermidis

Question 6

You are working up a male genital culture.

You see no growth on the blood agar plate but small colonies growing on the chocolate agar plate. The gram stain shows gram negative cocci in pairs.

Which test will you do next?

a) oxidase

b) motility

c) catalase

d) indole

Question 7

You are working up a cerebrospinal fluid culture.

You find colonies growing on blood agar as well as chocolate agar.

The colonies are oxidase positive gram negative cocci.

The colonies ferment glucose and maltose but not sucrose or lactose.

You identify the pathogen as

a) Neisseria meningitidis

b) Haemophilus influenzae

c) Streptococcus pneumoniae

d) Neisseria gonorrhoeae

Question 8

You are working up a urine culture.

You see >100 colonies that are gray and flat on the blood agar plate and >100 colonies that are bright pink on the MacConkey agar.

The IMViC results are Indole positive, Methyl Red positive, Vogues-Proskauer negative, Citrate negative.

You have identified the pathogen as

a) Citrobacter freundii

b) Escherichia coli

c) Enterobacter aerogenes

d) Proteus vulgaris

Question 9

You are working up a stool culture.

On MacConkey agar you see many bright pink colonies and many clear colonies.

Which colonies are potential pathogens that require further testing?

a) Clear colonies, non lactose fermenters

b) Bright pink colonies, non lactose fermenters

c) Bright pink colonies, lactose fermenters

d) Clear colonies, lactose fermenters

Question 10

DNA technology is useful in the identification of :

a) pathogens that are unable to be grown readily on artificial lab media.

b) pathogens that are no longer alive in the patient sample,

c) species that cannot be differentiated by conventional testing.

d) All of the above.

Question 11

You are preparing a sample of DNA from an unknown colony of bacteria.

After adding digestion buffer and incubating for the time suggested by the manufacturer, you centrifuge the sample.

The DNA is found:

a) stuck to the gel in the tube.

b) stuck to the sides of the tube.

c) in the pellet in the bottom of the tube.

d) in the supernatant in the tube.

Question 12

Which of the following is not true of the Polymerase Chain Reaction?

a) PCR is facilitated by a heat labile DNA polymerase.

b) PCR is a method of replicating DNA in a test tube.

c) PCR can facilitate the detection of DNA that is too low to detect by other methods.

Question 13

Why are dATP, dCTP, dTTP and dGTP added to a PCR reaction tube?

a) They catalyze the polymerase.

b) They buffer the mixture.

c) They allow the DNA in the sample to anneal.

d) They provide the building blocks of DNA.

Question 14

Why are universal 16S rDNA primers used in your experiment?

a) They will anneal to highly conserved areas of the gene that encodes bacterial 16S rRNA.

b) They will anneal to unique sequences of genes encoding 16S rRNA in specific bacteria.

Question 15

If universal primers are used to amplify DNA in a PCR reaction, then the PCR product must be sequenced to determine the bacteria that the DNA belongs to.

True

False

Question 16

How is the PCR product separated from the PCR mixture at the completion of the reaction?

a) Perform electrophoresis in an agarose gel, stain the gel and cut the band corresponding to the PCR product from the gel.

b) Pour the PCR mixture into a commercially prepared DNA microconcentrator column and follow the manufacturer’s directions to adhere and elute the PCR product from the column.

c) Both of the above procedures may be used.

d) Neither of the above procedures may be used.

Question 17

Your PCR product was sequenced by a method known as Cycle Sequencing.

Which of the following statements is false?

a) An automatic sequencer performs electrophoresis and reads the tagged DNA pieces, providing a read out of the nucleotide bases comprising the DNA sequence of the fragment being tested

b) Cycle sequencing is done in a PCR machine.

c)Tagged terminator nucleotides facilitate the creation of a series of nested DNA sequences of different length.

d) Cycle sequencing can be completed in just one test tube.

Question 18

The National Library of Medicine has a databank called GenBank that has deposited in it the DNA sequences of numerous genes isolated from known bacterial species.

True

False

Question 19

You obtained the following BLAST data from your sample:

99.9% Enterobacter sakazakii

95.2% Enterobacter aerogenes

93.7% Enterobacter cloacae

The pathogen in your sample is:

a)Enterobacter sakazakii

b)Enterobacter aerogenes

c)Enterobacter cloacae

d)Enterobacter species

Microbiology Lab Questions

 

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Microbiology. Please answer original forum with a minimum of 250 words

respond  student with a minimum of 100 words separately

please follow directions or I will dispute

original forum

Methods to preserve our foods has been a problem of mankind since we settled into groups and began to store our foods to eat at later times. As we stored our food to eat later, mankind often came back to collect his food only to find that microbes, which are ever-present, had already eaten it.

We know about expiration dates on foods and by now in the class, we understand that with microbes, it is a race between how fast one species grows against another. We eat the food before the microbes grow beyond a certain point (spoil the food with their waste by-products).

Some foods store for longer than others and depending on natural and some less than natural processes, we can extend the amount of time a food can be kept before microbes will take over and spoil the product. Keeping produce fresh for long periods of time has been a problem since one cannot treat fresh fruits and vegetables without altering the taste and texture.

A new and somewhat controversial method of food preservation, particularly produce, is gamma irradiation. This method uses high energy gamma radiation to treat food and has shown great promise in extending the shelf-life. Gamma irradiation is approved for use and does not show any ill effect on the produce itself.

Proponents of gamma irradiation claim that the method is safe, extends shelf life, and leaves no residue or otherwise dangerous chemicals on produce. Opponents argue the use of gamma irradiation is not safe, the facilities where produce is treated is not the proper place for this type of radiation to be released and exposure of the workers is likely.

Review Chapters 8 and 12 of your textbook on Microbial Metabolism and Modern Applications

Review these facts from the FDA on Food Irradiation

In this forum, choose a side; pro or con for gamma irradiated food. Choose to defend the use of gamma radiation as safe to use and safe to consume foods. OR, choose to oppose the use and consumption of foods treated in this manner.

Topic 1: Pro Gamma Irradiation of Food

Topic 2: Against Gamma Irradiation of Food

Address the following questions;

-Would you eat gamma-irradiated strawberries?

-Gamma-irradiation does extend the shelf-life but after some time, mold does begin to grow. Where does the mold come from?

-Was the mold already present on the strawberries and the growth slowed by the gamma irradiation?

-If gamma irradiation becomes the standard for processing produce, over time will the constant radiation exposure select for resistant strains of microbes that will eventually be able to grow despite gamma radiation? Why or why not?

-What about agricultural workers safety? Who is looking out for the women and men responsible for gamma irradiation of produce?

________________________________

Student Response

kyle

I am against gamma irradiation for foods even if it prolongs the shelf life of the food. We have so many altered and genetically modified food in our grocery stores it seems like gamma irradiation is the next step for food to become less natural and more modified. While it slows down the process of spoiling it also makes the food less nutritious. It kills the bad bacteria but also damages the fruit or vegetable as a whole. It’s like putting hydrogen peroxide on a wound. You may think it’s doing a good job by killing all the bacteria in your wound but it’s also killing all the good bacteria helping to fight against infection. So no, I will not eat a gamma-irradiated strawberry. Mold can still be present in the food because the radiation only kills most of the bacteria. After a while, the bacteria that wasn’t killed begins to grow and causes the food to spoil and rot. Gamma irradiation is supposed to kill the bacteria so if mold had begun to grow it would just stop it in whatever stage it was in. In the long run, a lot of scientists fear that the more gamma irradiation is done that the bacteria will begin to morph. Just like superbugs that we talked about a few weeks ago. The more you try to stop something the more chances it has at evolving and becoming resistant to the irradiation. Another large concern is the workers. Prolonged studies will have to be done to see if overexposure caused any damage, but it seems like an easy fix to just not be exposed. There is a long history of people being exposed to things that “experts” said was not harmful and ended up giving them cancer. It seems like an easy fix to just eat our food fresh and if we can’t then find food that has a longer shelf life without modifying it.

Center for Food Safety and Applied Nutrition. (n.d.). Consumers – Food Irradiation: What You Need to Know. Retrieved from https://www.fda.gov/food/resourcesforyou/consumers/ucm261680.htm

Christy

It’s good to look at both sides of this topic. Most of us have been consuming gamma irradiated foods and may not realize it. This type of food preservation technique has been in used widespread for more than fifty years. The good thing is that gamma irradiation is considered safe for the food it treats since it’s only the energy from the radiation that is treating the microbial growth and not the source of the radiation itself. For those who are proponents, they point out that it’s a cleaner-type of treatment for delicate produce since it’s likely been less-treated with other chemical inhibitors after gamma irradiation because it does not need further treatment.

Many are concerned about what’s on what they eat and are concerned that gamma radiation alters nutrient content (Maraei and Khaled, 2017). Presumably, gamma irradiated produce should be cleaner in terms of fewer pesticides. Would there be a way to test this to see if gamma irradiated produce has fewer chemicals than non-gamma irradiated produce?

Enjoy your day, Dr. Franklin

References

Maraei, Rabab and Elsawy, Khaled. (2017). Chemical Quality and Nutrient Composition of Strawberry Fruits Treated by Gamma Radiation.Journal of Radiation Research and Applied Sciences, Vol. 10, Iss. 1, 2017.

Microbiology

 

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