#2 Please, full and clear answers for the questions. Please, full and clear answ
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#2 Please, full and clear answers for the questions.
Please, full and clear answers for the questions.
CASE STUDY The Spread of a Drug-resistance Gene a. A plasmid showing the NDM gene and clusters of drug- resistance genes A Rhode Island resident (patient 1) travelled to Cambodia, where she was diagnosed with spinal cord compression and was hospitalized from December 20 to 30. She had an indwelling catheter placed during her medical care and was given mul tiple antibiotics. On January 6, she returned to Rhode Island and was hospitalized for lymphoma. She underwent chemother- apy and required prolanged bladder catheterization and was given more than 20 different antibiotics during her treatment On March 4, a urine culture grew Klebsiella pneumonise containing the New Delhi metallo-beta- lactamase (NDM0 gene NDM-carrying plasmid 1. How does antibiotic therapy reveal the presence of drug resistant bacteria? The drug-resistance gene NDM was first reported in a pa- tient who had been hospitalized in New Delhi, India, in 2007. Re sistant bacteria carrying NDM are of particular concern because NDM resistance genes are usually encoded on plasmids that har- bor multiple resistance gene clusters and are transmitted easily to other genera of bacteria (Figure al. KEY Antibiotic resistance gene and direction of transcription New Delhi metalo-beta-lactamase gene l Location of an insertion sequence Plasmid DNA Regions of DNA insened into plasmid Transposons often carry one or more antibiotic re- sistance genes. genetic elements for moving and combining antibiotic Transposition A transposon is a segment of DNA that is capable of in- dependently replicating itself and inserting the copy into a new position within the same chromosome or another resistance genes onto plasmids. This enables plasmids to chromosome or plasmid. sequences known as insertion sequences that are essen- tial for transposon movement. and inserting the colements for newult ransposons ar Transposons contain genetic multidrug-resistant pathogens (see the Case Study). Transposition is caused by the movement of a trans- poson from one genetic location to another in a cell. Transposition of a transposon combines both recombi- nation and mutation. Transposition recombination event in that genetic information is being recombined into a new site. If a transposon moves from the chromo 2. Why are horizontal gene transfer and recombina- some to a plasmid, it can then be more easily transferred tion important for the rapid evolution of bacteria? to other cells during conjugation. Transposition can also 3. Why is the movement of cause mutation if a transposon inserts into a new site that tant disrupts a gene, causing its inactivation. CONCEPT CHECK STOP tion is a recombination 1. How does UV light cause mutations? transposons impor- in the development of multidrug-resistant 224 CHAPTER 8 Microbial Genetics and Genetic Engineering
Explanation / Answer
Image 1.
How does antibiotic therapy reveal the presence of drug-resistant bacteria?
Antibiotic therapy is provided to a patient generally after some surgery to prevent any infection. But there is always a chance that patient may not respond to the therapy. Then physicians may conclude that the patient may have multidrug resistant bacteria infected. Then blood and urine samples are collected from the patient to test in lab, what type of resistant bacteria is present and resistant to how many drugs. Then they try to find any antibacterial drug present that can kill that resistant strain.
How does UV light cause mutation?
UV light is high energetic electromagnetic wave. It has destructive properties when a cell has absorbed them. UV A ray is the most damaging. It can create a pyrimidine-pyrimidine dimer on a strand of a DNA. It occurs when two adjacent pyrimidine on a strand absorb the energy from the UV ray and forms dimer (C=C or T=T), for e.g.
5’-ACTGCTC^CGTAATCG-3’
3’-TGACGAGGCATTAGC- 5’
Now when this DNA strand undergoes replication, the replication machinery cannot replicate through the upper strand in the given example, and have to stop, unless a bypass mechanism comes to rescue and forcefully adds some nucleotide. But often bypassing enzymes are error prone which can add non-complimentary bases. And thus a mutation occurs.
Why are horizontal gene transfer and recombination important for the rapid evolution of bacteria?
Horizontal gene transfer is a process where bacteria can acquire a gene from other bacteria other than replication of parent genome. Mechanisms by which they transfer genes are Transformation, Transduction, and Conjugation.
Recombination is a process by which a genetic material is mixing up within the genome. Recombination can create new traits, also can produce genetic disease. Meiosis is the process where recombination occurs in eukaryotic organisms. In prokaryotes it is rather simple.
Bacterial evolution is also called microevolution. Bacteria can seriously get benefit from horizontal gene transfer. Bacteria from one community which have already produced new traits by recombination, can donate (conjugation), or release (transformation) this new trait via transferring its genetic material to a community of bacteria which still has not develop that trait. For example, when a bacterial colony produces antibacterial drug resistance, by continuously remaining in exposure of that drug, can transfer the gene to a colony which still has not come into exposure of the drug. By doing that, the second colony can get resistant to that drug beforehand.
Why is the movement of transposons important in the development of multidrug resistant pathogens?
Multidrug resistance can occur by accumulating of drug resistance plasmids from multiple sources, or it can also occur via transposons. Transposons are a gene or DNA element which can move within genome. Transposons can create mutation, multiply copy of a gene or even can change the orientation of a gene. Transposons of a drug resistant gene thus can create multiple copy of itself, or can even create a new sequence which produces a resistant gene to a different drug; as drug resistant gene transcripts are modified versions of each other. Thus transposons help create multi drug resistant bacterial species.
Image 2
How did some Klebsiella bacteria probably acquire the NDM gene and the multidrug resistance characteristics shown in the diagram?
Klebsiella may have acquired the drug resistance characteristic via horizontal gene transfer. As the resistant gene NDM is situated in plasmid, most probably it came in the process of Transformation. Transformation is a process where a bacteria can uptake plasmids from environment (mostly comes from dead bacteria) via transporter present on bacterial membrane. Once it is in the cytoplasm, they can replicate to produce more of this plasmid and make it their own. Also they can acquire the gene via Conjugation method, where a bridge between a donor and recipient bacteria establishes and the plasmid can then be provided by the donor bacteria. Also it is possible that transposons help create the multidrug resistant characteristic of the plasmid.
What does the abundant amount of insertion sequences imply about the how the plasmid acquired the many other drug resisted genes?
If the first drug resistant gene was present under a transposon, then there are high chances that the gene duplicated itself via trans-positioning. Insertion sequence is part of transposons that help them fuse with genome. Abundant amount of insertion sequence implies that multi drug resistance genes occurred via transposons moving into different positions.
Based on the information in the table propose a theory on how the NDM gene was spread in the hospital.
Based on the information given it is clear that nursing stuff has in contact with both patients. So if the patient 1 has multidrug resistant bacteria it is highly possible that they were transferred via the touch of nursing stuff from patient 1 to patient 2. It is also possible that the nursing stuff has distributed objects with the bacteria. As bacteria is resistant to most of the known antibacterial drugs, the other patients who are now contaminated, may allow them to thrive as they are on low dose of antibacterial drug or may be not at all.
Image 3
Describe the paralysis seen in the photos?
The paralysis shown in the image is most probably Flaccid Paralysis.
Which cells would have survived in the tofu after boiling?
Boiling of food can kill most of the pathogen inside. But it cannot kill Endospores. Endospore are dormant state of some pathogenic bacteria, where they dehydrate themselves and create a protein coat outside them to protect from heat, various chemical agents. Also they produce some chemical agents to protect their genetic material. C. botulinum is one such species which can create endospore. They mainly are food borne bacterial species. So if they remain in spore state inside food, boiling will not harm them, and they will be ingested along with food. Then they can reflourish and infect the eater.
Name the disease that is affecting this couple.
Botulism is the disease caused by C. botulinum, by a neurotoxin produced by them. This neuro toxin can paralyze muscle and can be fatal.
What are the early signs and symptoms of the disease?
The early signs and symptoms include, Nausea, vomiting, and diarrhoea. After some days they will feel weakness in muscle, dizziness, double vision, and dysphagia.
In general how this disease is normally prevented?
The most important prevention is avoiding canned food; they are the main source of these bacteria. Eating healthy and fresh cooked food is always better. Boiling of the food before eating is always preferable, and also not consuming spoiled or expired food. Keeping cooking station, utensils clean will definitely help preventing the bacterial generation.
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