microbiology lab final
Which reagent was used to wash the ELISA plate?
PBS
Any substance that induces the production of antibodies is called a/an
antigen
Which of the following statements is true about PCR?
- An automated PCR machine is called a thermal cycler. -The DNA polymerase used in PCR has to be able to withstand high temperatures. -Each PCR cycle doubles the amount of DNA in the sample. All of the above are true.
Which of the following would affect the size of a zone of inhibition around an antiseptic or disinfectant disk?
- The concentration of chemical in the disk - How quickly the chemical diffuses through the agar - The depth of the agar - The susceptibility of the microorganism to the chemical
Betadine, an iodine compound used to scrub skin before a surgical incision, is considered a(n)
antiseptic
Which structures are less susceptible to UV damage? (Pick two.)
-Protozoan cysts -Endospores
Which of the following are limitations of an ELISA? Check all that apply.
-Some people may be poor producers of an antibody and therefore the antibody level may be too low to measure or detect. -A positive result does not necessarily mean that a patient is sick. A positive result may occur if an unrelated antibody reacts with a non-specific antigen. -The body can continue to produce antibodies even though the person may have had the disease previously and recovered.
Which of the following apply to the development of streptomycin resistance in E. coli?
-The E. coli population has genetic variation. -The selective agent is streptomycin. -The mutation resulting in streptomycin resistance is random
What cellular structures or processes can be targeted by a microbial control method?
-The cell wall -The cell membrane -Protein synthesis -DNA synthesis -Metabolic pathways
Which of the following are limitations of using UV radiation for disinfection?
-UV radiation does not penetrate through paper, plastics, or liquids -UV radiation can damage the skin and eyes
Which of the following white blood cell(s) is/are classified as a granulocyte? Check all that apply.
-basophil -eosinophil -neutrophil
Which of the following is found in a PCR MasterMix?
-dNTPs -buffer -oligonucleotide primers
Which of the following white blood cell(s) is/are classified as an agranulocyte? Check all that apply.
-lymphocyte -monocyte
Which of the following enzymes can neutralize reactive oxygen species?
-peroxidase -superoxide dismutase -catalase
Which of the following can cause oxidative stress?
-peroxide -hydroxyl radicals -superoxide radical (lab23)
Which of the following is/are classified as a formed element of blood? Check all that apply.
-platelet -red blood cell -white blood cell
Match the temperature of the thermal cycler to the correct step in a PCR reaction. 1. Denaturation of DNA strands 2.Elongation of the DNA strand 3. Attachment of primers to the template DNA
1. 94°C 2. 72°C 3. 60°C
Place these types of bacteria in order of their susceptibility to chemical disinfection, from least susceptible to most susceptible.
1. Bacterial endospores 2. Acid-fast bacteria 3.Gram-negative bacteria 4.Gram-positive bacteria
Place the steps of the microbial identification lab in the correct order.
1. Isolate bacterial DNA 2.Amplify DNA in a PCR reaction 3.Purify the DNA product 4.Sequence the DNA 5.Analyze the sequenced DNA
Match the description of each WBC. 1. Polymorphonuclear (=nucleus twisted and segmented); slightly pinkish granular cytoplasm 2. Large round nucleus takes most of the space in the cell; small cytoplasm ring around nucleus. 3. Large cell, twice as big as a red blood cell. Nucleus is "bean" or "C" shaped. 4. Cell full of red-pink staining granules; nucleus is bilobed (=two lobes). 5. Cell is full of dark-purple staining granules; nucleus is bilobed (=two lobes).
1. Neutrophil 2.Lymphocyte 3.Monocyte 4.Eosinophil 5.Basophil
Identify the primary and secondary antibodies used in the ELISA lab. 1. Antibodies to SLE that may be present in the patient's blood 2. HRP-tagged rabbit anti-human antibody
1. Primary antibody 2. Secondary antibody
Match each of the following to the correct purpose. 1. Prevents DNA polymerase from adding more nucleotide bases to the growing DNA molecule. 2.Adds new nucleotide bases to the new DNA strand using base-pairing rules. 3.Lab equipment used to spin down samples. 4.Binds to template DNA and allows DNA polymerase to start elongating the new strand of DNA. 5.Used to make sure that the PCR sample was prepared correctly. 6.Separates DNA fragments by size.
1. Terminator bases 2. DNA polymerase 3.Centrifuge 4.Primers 5.Positive control PCR tube 6.Capillary tube in sequencing machine
1. Sterilization 2. Disinfection 3.Antisepsis
1. The destruction of all microbial life 2. Removal of all vegetative pathogens from an inanimate object 3. Removal of all vegetative pathogens from living tissue
Match the blood type and antibodies that would normally be present in a person's plasma. 1. Anti-A and anti-B antibodies in plasma 2. Anti-B antibodies in plasma 3. Anti-A antibodies in plasma 4.No blood type antibodies in plasma
1. Type O Blood 2. Type A Blood 3. Type B Blood 4. Type AB Blood
Place these steps in the order in which they will be performed when setting up a disk diffusion assay to test the effectiveness of disinfectants and antiseptics.
1. Using a swab, inoculate a suspension of the bacteria being tested onto an agar plate, spreading the inoculum over the entire surface. 2. Saturate sterile filter paper disks with the test chemical (disinfectant or antiseptic) and place onto the inoculated agar plate. Repeat with each chemical being tested. 3. Incubate inoculated agar plates overnight to promote bacterial growth. 4. Observe plates to determine the presence of a zone of inhibition around each antiseptic or disinfectant disk.
Place the main steps in the ELISA protocol in order from the first step to the last step.
1.Add patient's serum to pretreated ELISA plate. 2.Add the secondary antibody-enzyme conjugate. 3.Add the substrate
The polymerase chain reaction consists of repeating cycles of the same three steps. Arrange those steps in the correct order.
1.Denaturation 2.Annealing 3.Extension
In order for natural selection to occur, a few criteria have to be met. Match the following criteria to how they apply in to the selection for antibiotic resistance.
1.Some bacteria are resistant to antibiotics while other bacteria are not. 2.The ability to resist antibiotics is due to a gene that will be replicated and passed on everytime the bacterium divides. 3.In the presence of antibiotics, bacteria that are resistant to the antibiotic survive while those that are not resistant will die.
Rank the following white blood cells from least numerous to most numerous.
1.basophils 2.eosinophils 3.monocytes 4.lymphocytes 5.neutrophils
1. optimum growth temperature: −5°C-20°C 2. optimum growth temperature: 20°C-50°C 3. optimum growth temperature: 50°C-80°C 4. optimum growth temperature: 80°C- >100°C
1.psychrophile 2.mesophile 3.thermophile 4.hyperthermophile
1. These organisms are likely to inhabit a compost pile that is actively composting. 2. The bacteria that grow in and on the human body are in this group. 3. These organisms might grow in the superheated water near hydrothermal vents in the ocean floor. 4. These organisms might be isolated from water pools on the surface of a glacier.
1.thermophile 2.mesophile 3. hyperthermophile 4.psychrophile
Which of the following rDNA molecules was sequenced and used to identify the bacterial DNA sample in the lab simulation?
16S
To allow the primary antibody to bind to the antigen, the ELISA plate is incubated at
37°C.
You are studying a bacterium found in the normal intestinal flora of humans and most other mammals, and are doing an experiment to determine the optimum growth rate of this bacteria. You have inoculated five nutrient broths, and are incubating one broth at each of the following temperatures: 5°C, 25°C, 38°C, 42°C, and 55°C. At which temperature would you predict to see the optimum growth rate?
38°C
What is the purpose of water in the experiment?
A negative control
ELISA can be subject to many different errors. One is that biological and chemical reagents can change with time. Which of the following will help ensure you do not have this type of error?
A positive control
How are agar plates inoculated for disk diffusion testing of antiseptics and disinfectants?
A swab is used to inoculate the entire surface of the plate, producing a lawn of growth.
Obligate aerobes require oxygen in order to generate
ATP
How is an antiseptic different from a disinfectant?
An antiseptic is used to remove or kill microorganisms on tissue, whereas a disinfectant is used to remove or kill microorganisms on inanimate objects.
What is the disk used for in this exercise?
Applying a certain chemical to the bacterial lawn
Where would you expect obligate anaerobes to grow in an FTM culture tube?
At the bottom
The surface of red blood cells and a person with type B blood has
B antigens
Let's say you inoculate four agar plates, each containing a different antibiotic (A, B, C, and D), and you add a swab from a lesion taken from a patient. After incubating the plates, you observe that plate A has only a few colonies, while the others all have many colonies. How do you interpret the results?
Bacteria in the patient's sample are susceptible to antibiotic A but not B, C, and D
How does an antibiotic act as a selective agent in promoting bacterial resistance?
Bacteria with a random mutation that allows resistance to that antibiotic are able to survive exposure and reproduce, passing the resistance mutation on to subsequent generations of bacteria.
Are antibiotics bactericidal or bacteriostatic?
Bacteriostatic or bactericidal
Why is it necessary to remove the lid of the petri plate before exposing it to UV light?
Because UV light has poor penetrating ability
If you test ten different gram-positive and gram-negative organisms and find that almost all of them are sensitive to a particular drug, what would be that drug's spectrum of activity?
Broad-spectrum
Which of the following DNA sequences would be the most likely to be damaged by UV radiation?
CTTGAATTAA
Which of the following processes might be affected by the presence of thymine dimers?
DNA replication and protein synthesis
What is used to sterilize the forceps in this exercise?
Ethanol and then briefly pass through flame
Upon experiencing itchiness and redness in your eyes accompanied by discharge, you go to your doctor. She diagnoses the condition as conjunctivitis (pinkeye) and prescribes a course of Polytrim eyedrops, which is a combination of polymixin B and trimethoprim. She tells you to use the eyedrops twice a day for 10 days. However, after three days, your symptoms have gone away and you feel much better. Is it advisable to stop applying the eyedrops? Why or why not? Please explain your answer in detail.
Even if you feel better, it's best to keep using the medication regularly in order to get the most benefit from it. Stopping the medication too soon may allow the bacteria to continue to grow, which may result in a return of the infection and the bacteria may be resistant to antibiotics. OR "I would advise not to stop applying the eyedrops. Bacteria are killed at a constant rate. If you do not kill all of the bacterial cells, they will become less resistant. Therefore, the bacterial cells that are left are typically the strongest due to their survival, and the weakest bacterial cells were already killed from the eyedrops. Even if there is a single cell left, there is a great chance that it will multiply and result in the infection staying or even getting worse."
How will you select and grow a resistant strain of E. coli in this experiment?
Expose a sample of E. coli to streptomycin by inoculating it onto a streptomycin positive plate. Any colonies that grow will carry a mutation for resistance.
A positive ELISA result means that the antibody is present and therefore the patient has the disease.
FALSE
Adding an antibiotic to a nonresistant population of bacteria induces a mutation that leads to new, resistant genes.
FALSE
All DNA mutations are harmful to the organism.
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
Obligate anaerobes have enzymes like superoxide dismutase that can neutralize toxic oxygen byproducts.
False
The organism inoculated onto the plates was likely a facultative anaerobe
False
The purpose of disinfection is to kill all the microorganisms on an inanimate object.
False
Does a microbial control method have to be a sterilant in order to be useful? Why or why not?
Not all control methods need to be sterilants because reducing the number of pathogenic/harmful microbes can also be sufficient.
Based on the following image, are gram-positive or gram-negative bacteria more susceptible to chemical disinfectants? What cellular characteristic might explain that difference in susceptibility?
Gram-positive is more susceptible because it has a bigger zone of inhibition for all disks and gram-negative has much smaller zone of inhibition than gram-positive. The cellular characteristics that can explain the difference in susceptibility will be the cell wall because for gram-positive its not as protective since it doesn't have the outer shell layer while gram-negative is more protective because it has an extra layer of lipid membrane thta makes it harder for bacteria cells to come in.
In which of the following situations is it reproductively advantageous for bacteria to have streptomycin resistance genes?
In the presence of streptomycin.
Which of the following best describes the mechanism of action of the antibiotic streptomycin?
It disrupts protein synthesis in nonresistant bacteria.
Some microbial control methods involves the application of heat, such as autoclaving, boiling and pasteurization. Is the application of heat beyond the organism's maximum growth temperature bacteriostatic or bactericidal? Why?
It is bactericidal because the heat kills all of the organisms that is on the item. (not done)
Please choose the method of antimicrobial susceptibility testing that involves measuring and evaluating zones of inhibition around antibiotic disks placed on a culture of bacteria prior to incubation.
Kirby-Bauer test
Why is it that some microorganisms do not need oxygen in order to grow?
Microorganisms that do not need oxygen use other inorganic molecules as a final electron acceptor in an electron transport chain or use fermentative pathways to generate ATP.
After running your very first ELISA test, you observe that there was a color change in the wells containing your negative control. What might be a possible explanation for this result?
Negative controls are there to test for contamination; they have water instead of serum; therefore, it shouldn't result in any positive reaction. If, after running your very first ELISA test, you observe that there was a color change in the wells containing your negative control, the possible explanation for this result could have been that you got a positive reaction in the (-) control, which indicates you might have contamination or that something went wrong in the experiment.
P. aeruginosa infection in the lungs
Obligate aerobe
Bacteroides that grows mutualistically in the gut
Obligate anaerobe
___________ __________ lack the required enzymes needed for using oxygen in respiration and and do not have enzymes to neutralize toxic oxygen species. (The answer contains two words.)
Obligate anaerobes
Which of the following is false about the DNA isolation step?
Only specific portions of the bacteria's DNA is isolated.
Why is oxygen a growth requirement for some microorganisms?
Oxygen is necessary for some bacteria as a final electron acceptor in an electron transport chain to produce ATP. This step is required to provide power to cellular functions. Without oxygen, these organisms cannot generate ATP and will die.
Which of the following enzymes will protect a cell from oxidative damage?
Peroxidase
E. coli bacteria was spread on both agar plates and incubated for 24 hours. If you wanted to grow up a large quantity of streptomycin resistant E. coli, what would you do next?
Pick a colony of bacteria from the streptomycin positive plate and grow it on a streptomycin positive plate.
In the HHMI ELISA assay, a color change indicates the presence of antibodies that are specific for
SLE
What does the amount of color reflect?
The amount of antigen initially present
What information does the Kirby-Bauer method provide?
Sensitivity and resistance to antibiotics Correct
Why do we use different dilutions when performing ELISA?
Serum that too diluted may result in a false-negative result, because the level of antibodies in the sample may be too low to detect.
The genus of microorganism responsible for producing the most antibiotics so far is
Streptomyces
An individual with blood type O lacks both RBC antigens A and B.
TRUE
Blood is a biohazard that requires special safety precautions.
TRUE
A 4-year-old comes to the ER with signs and symptoms indicating a lower respiratory tract infection. The patient is given a full course of penicillin but returns two days later with no improvement. After performing a bacterial culture, you find that the patient has a Haemophilus influenzae bacterial infection. H. influenzae is a gram-negative bacterium. Based on this new information, what antibiotic would you prescribe next, and why? Use the following figure to justify your answer.
The antibiotic I would prescribe would be carbapenems. It has the broadest range in the gram-negative bacteria which means it can fight more types of infections compared to the narrow antibiotics.
E. coli bacteria were spread on both agar plates and incubated for 24 hours. What does this image tell you about the bacteria?
The bacteria were susceptible to streptomycin.
Clostridium, a known obligate anaerobe, does not grow in the GasPak jar. What might be the reason for this lack of growth?
The chemical reaction failed to remove all of the oxygen in the jar.
Why do bacteria only grow within a certain range of temperature? In other words, why can't they grow below their minimum temperature or above their maximum temperature?
The minimum temperature will cause the microbe to not grow because it will not be able to catalyze reactions (there's not enough energy to catalyze reactions) and the maximum temperature will just kill the microbe because it will denature its proteins.
What is being counted in a differential white blood cell count?
The percentages of different types of white blood cells as a fraction of white blood cells
What is the purpose of the negative control PCR tube?
The purpose of the negative control PCR tube shows if contamination of the PCR experiment with foreign DNA has occurred.
What is the purpose of the positive control PCR tube?
The purpose of the positive control PCR tube is to show that the primers have attached to the DNA strand.
What is used to compare the effectiveness of each chemical?
The zone of inhibition around the diskCorrectCorrect
Mueller-Hinton agar plates are poured to a uniform thickness of 4mm. Zone size interpretive criteria are based on Mueller-Hinton plates of this thickness. If a plate had been poured that was 7 mm thick, how would this affect the size of the zones of inhibition?
The zones would be smaller
Why do some microorganisms die when exposed to oxygen?
This is called oxygen toxicity, they do not possess the defenses that make aerobic life possible which then means they can't survive in air. The singlet oxygen molecule is very reactive and means that superoxide must be removed for the cells to survive in the presence of oxygen. (not done)
What is the purpose of a polymerase chain reaction?
To amplify small amounts of DNA for analysis.
What is the purpose of the digestive buffer used during the DNA isolation step?
To break down bacterial cell walls.
Why is antimicrobic sensitivity testing done?
To determine what antimicrobials would be most effective for treating the infection
Tim has an accident and needs a fast blood transfusion. Tim's blood type is "B". The hospital ran out of type B blood, but they have AB type, A type, and O type blood. Which type would Tim receive as it will provide the least issues for him?
Type O Blood
What will be the variable in the four quadrants of the plate?
Type of antiseptics
What describes the method used to create a bacterial lawn in this experiment?
Using a sterile swab to inoculate the entire surface of a plate
While running an ELISA test, you forget to wash the microtiter plate after adding the primary antibody. Will this mistake lead to a false positive or a false negative result? Why?
Washing it will remove any proteins that have not bound to the microtiter plate and any anti bodies that have not bound to their targets, therefore preventing unbound proteins. This unbound antibody must be removed, because the anti-human antibody added in the next step will recognize and react with any antibody remaining in the well. A reaction with non-SLE antibody will produce a false-positive result.
Where would you predict an obligate anaerobe would grow in a tube of fluid thioglycolate medium?
at the bottom of the tube
Natural selection occurs when
a new genetic variation occurs that allows individuals to have a reproductive and survival advantage.
With respect to oxygen requirements, an _____________ can use gaseous oxygen and possesses enzymes to process toxic oxygen products.
aerobe
__________ occurs when blood is mismatched during a transfusion.
agglutination
What would you expect to happen if a transfusion recipient had blood type O and a donor had blood type AB?
agglutination of the donor blood would occur
What type of environment is created in the GasPak jar?
anaerobic
The plasma of a person with type A blood has:
anti-B antibodies.
Penicillin is made by a fungus and used to kill bacterial cells. Therefore, penicillin is an example of a(n)
antibiotic
The purpose of the ELISA test in the HHMI lab simulation is to test for the presence of specific
antibodies
Low temperatures are _____________ while high temperatures are _________________ for bacteria.
bacteriostatic; bactericidal
. An antimicrobial that is effective against many types of pathogenic bacteria would be considered a _______ agent.
broad-spectrum
The instrument used to separate the different phases in a blood sample is called a
centrifuge
Going above the maximum temperature for an organism will cause proteins to _________________ and lose their function.
denature
The chemical that you use to wipe down your lab bench at the beginning and end of a lab exercise is an example of a(n)
disinfectant
Which choice below briefly describes the Kirby-Bauer method of antimicrobic sensitivity testing?
disk diffusion
Where would antibodies be found in the blood?
dissolved in the plasma
How is the terminating nucleotide in a DNA fragment "read" by the sequencing machine?
each nucleotide base emits a different fluorescent color
A bacterial species that cannot tolerate the presence of oxygen and will only grow in the absence of oxygen is classified as a(n)
obligate anaerobe
In an ELISA assay, a color change is caused by the binding of which two molecules?
enzyme-substrate
____________ anaerobes can grow in the presence or absence of oxygen, but grow better in its presence.
facultative
E. coli grows throughout an FTM tube. What would be its oxygen preference classification?
facultative anaerobe
If an organism grew on both plates in this experiment, what is its classification?
facultative anaerobe
Some organisms exhibit flexibility in terms of their energy harvesting reactions. If provided with oxygen, they will obtain energy through aerobic respiration. If in an environment without oxygen, they will turn to fermentation to satisfy their energy needs. These organisms are classified as
facultative anaerobes
A large zone of inhibition around a disk containing disinfectant generally indicates that the bacteria being tested is resistant to the disinfectant.
false
Organisms that do not use oxygen as a final electron acceptor use ___________________ pathways to generate energy instead.
fermentative
The greater the turbidity of a culture broth, the greater the __________ _________ of the bacterium. Answer has two words.
growth rate
The greater the turbidity of a culture broth, the ______________ the growth rate of the bacterium.
higher
What is the name of the enzyme that is conjugated to the secondary antibody in the HHMI ELISA simulation?
horseradish peroxidase (HRP)
What problem is most likely the case when a person has a high count of lymphocytes?
infection
Which cell has a large nucleus that fills most of the cell?
lymphocyte
Both human pathogens and normal microbiota are typically classified as
mesophiles
Which of the following is the source of new, novel alleles in a population?
mutation
Which of the following mechanisms of change in gene frequencies is responsible for the antibiotic resistance of E. coli in this experiment?
natural selection
The surface of red blood cells in a person with type O blood has
neither A-antigens nor B-antigens.
Which white blood cell represents the greatest percentage in a normal differential count?
neutrophil
If the blood from an individual with type O blood is mixed with anti-A serum in one well and anti-B serum in a second separate well,
no agglutination will be seen.
An ___________ aerobe cannot grow without oxygen.
obligate
Which of the following is the likely classification for the organism in the FTM tube?
obligate aerobe
The temperature at which microorganisms grow the most rapidly is its
optimum temperature.
The first antibiotic to be discovered was
penicillin.
Which of the following is not a reactive oxygen species?
peroxidase
The formed elements that allow blood to clot are called ______.
platelets
What determines a person's blood type?
presence of antigens on the red blood cells
Listeria monocytogenes is a human pathogen, growing readily in the human body. It poses a problem in food storage because of its ability to grow in refrigerated foods, such as unpasteurized milk or deli meats. An organism that prefers moderate temperatures, such as 25-40°C but is capable of growth at refrigerator temperatures is known as a
psychrotroph
The essential transport of oxygen in our body is provided by the _____ blood cells.
red
After centrifugation, blood separates into two phases. Antibodies are contained in the liquid phase, known as
serum
UV light has ______ wavelengths than visible light waves, and its peak energy is at a wavelength of ______.
shorter; 254nm
The capillary tube in the sequencing machine separates DNA fragments by
size
Based on the following picture, which disinfectant was the most effective against Streptococcus agalactiae?
soap
Which of the following would be appropriately sterilized using UV radiation?
stainless steel surface in biological safety cabinet used for media preparation
If the blood from an individual with type AB blood is mixed with anti-A serum in one well and anti-B serum in a second separate well
the anti-A serum well and the anti-B serum well will show agglutination.
Two agar plates, one containing the antibiotic streptomycin and one without antibiotics, are inoculated with E. coli. After incubation, the streptomycin negative plate has many bacterial colonies, while the streptomycin positive plate has only a few colonies. Samples of the colonies from the positive plate are placed on another positive plate, and after incubation many colonies grow. In this experiment, what is the selective agent?
the antibiotic streptomycin
Taq polymerase is a DNA polymerase enzyme that demonstrates maximal activity at 72°C. The organism from which this enzyme was isolated would most likely be classified as a
thermophile
Where would you predict a facultative anaerobe would grow in a tube of fluid thioglycolate medium?
throughout the tube
When two adjacent thymine molecules are joined by a covalent bond as a result of exposure to UV light, this structure is referred to as a
thymine dimer.
A spectrophotometer measures the _________________ of a culture.
turbidity
The clear area devoid of bacterial growth around an antiseptic or disinfectant disk is referred to as the
zone of inhibition.