Microbiology: An Evolving Science (Fourth Edition)
4th Edition
ISBN: 9780393615098
Author: John W. Foster, Joan L. Slonczewski
Publisher: W. W. Norton & Company
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Chapter 6, Problem 7RQ
Summary Introduction
To review:
The plate count method for enumeration of bacteriophages and its modification for the measurement of animal and oncogenic viruses.
Introduction:
Viruses are dependent on host cells for their survival and reproduction. They cannot be grown in artificial culture medium due to their inability to replicate independently. However, certain manipulations in culturing method can be useful to detect and enumerate the number of virus in a given sample.
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During the incubation step of the plaque assay, viral replication leads to host cell lysis. This allows the freshly-released virions to diffuse through the media and infect new hosts. The amount of agar added to the top agar is 7 g per liter rather than the 16 g of agar per liter for most solid media, including the bottom agar used in this assay. How would it change the plaque assay results if bottom agar was used in place of the top agar in this assay?
a- The diameter of the plaques would be smaller.
b- The diameter of the plaques would not change.
c- The diameter of the plaques would be larger.
(2) A researcher measured the viral titer of PhiX174 in fish tank water, untreated sewage water, and unpasteurized apple juice. Which sample do you predict will have the highest titer on this page?
a- Fish tank water
b- Unpasteurized apple juice
c- Untreated sewage water
Which of the following is TRUE when one assay bacteriophage titers? You should:
a) first mix the phages with a live bacterial culture and then pour the mixture on the agar plate
b) directly add the phage dilution onto the surface of an agar plate
c) add tryptic soy broth to the phage dilution and incubate overnight
d) incubate a phage solution with live bacterial cells for several minutes. You must add soft agar to the mixture before pouring the content on the agar plate
You infect bacteria with two phages during a cis test. This produces a lysate that contains phage particles. Before you can
count outcomes, you need to work out the amount of phage to use in subsequent experiments. You start by making two ten-
fold serial dilutions of the lysate and then add 1mL of the final diluted lysate to a plate of permissive strain e.coli. You observe
10 plaques. How many phage per mL were present in the original lysate?
a. 10 phage/mL
o b. 3,300 phage/mL
c. 10,000 phage/mL
o d. 1,000 phage/mL
e. 33 phage/mL
Chapter 6 Solutions
Microbiology: An Evolving Science (Fourth Edition)
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- Why is there an inverse relationship between the dilution factor and the amount of virus in solution?arrow_forwardDiscuss the principles behind the use of the following techniques in the diagnosis of viral infections, providing examples of viruses diagnosed using these methods 5..1 ELISA 5.2 Restriction Fragment Length Polymorphism 5.3 Polymerase chain reactionarrow_forward10 mL of a bacteriophage suspension is mixed with 5 mL of a bacterial culture and 25% of the phages adsorb. The bacteriophage suspension has a concentration of 4x1018 viruses per mL, and the bacterial culture had a concentration of 6x1014 bacteria per mL. How many viruses are adsorbed per cell (multiplicity of infection)? What fraction of the cells is uninfected? What fraction of the cells is single infected? What fraction of the cells is multiple infected?arrow_forward
- Write a lab report on enumeration of lytic viruses : the plaque assay including the sections: introduction, Materials and Methods, Results and Discussion, and citing peer reviewed sources use this data for results section Group Number Number of Plaques Dilution Factor of Plate Original Concentration of Phage 1 58 10^3 5.80E+04 2 37 10^3 3.70E+04 3 44 10^3 4.40E+04 4 63 10^3 6.30E+04 5 36 10^2 3.60E+03 6 65 10^3 6.50E+04 7 260 10^2 2.60E+04 8 39 10^3 3.90E+04 9 178 10^2 1.78E+04 10 192 10^2 1.92E+04 11 274 10^2 2.74E+04 12 224 10^2 2.24E+04 Class Average 3.52E+04arrow_forwardWhat is the best advise for obtaining 2-log viral inactivation when the needed CT free chlorine is 60 min mg per L, CT chloramine is 11,000 min mg per L, and CT chlorine dioxide is 170 min mg per L? Considering these virus-inactivation approaches (chlorine dioxide, chloramine, and free chlorine).when using CT values to disinfect water assets following a water quality event, what biological elements and physicochemical aspects must be considered? Display the CT curve as well as the effect of increasing pH on inactivation kinetics, and estimate the CT values that will be needed.arrow_forwardExplain how PCR/OLA (polymerase chain reaction/oligonucleotide ligation assay) can be used in the diagnosis of sickle cell disorder . Would you recommend this method for routine diagnosis of sickle cell disorder? Explainarrow_forward
- In our pandemic world, COVID testing has become a very common thing (unfortunately necessary). When receiving a test to detect the COVID virus, a person may or may not have COVID, and the test result could come back either positive or negative. (a) Explain what specificity means in the context of a COVID test. (b) Explain what sensitivity means in the context of a COVID test.arrow_forwardWhat is the purpose of using Triton X in hemolytic assay.arrow_forwardIs it important to have fewer phages than bacterial host cells when doing a quantitative plaque assay? Explain.arrow_forward
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