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Bacterial conjugation, mediated mainly by conjugative plasmids such as F, represents a potential health threat through the sharing of genes for pathogenicity or antibiotic resistance. Given that more than 400 different species of bacteria coinhabit a healthy human gut and more than 200 coinhabit human skin, Francisco Dionisio [(2002) Genetics 162:1525–1532] investigated the ability of plasmids to undergo between-species conjugal transfer. The following data are presented for various species of the enterobacterial genus Escherichia. The data are presented as “log base 10” values; for example, –2.0 would be equivalent to 10–2 as a rate of transfer. Assume that all differences between values presented are statistically significant.
- (a) What general conclusion(s) can be drawn from these data?
- (b) In what species is within-species transfer most likely? In what species pair is between-species transfer most likely?
- (c) What is the significance of these findings in terms of human health?
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Concepts of Genetics (12th Edition)
- Which of the following statements is not applicable to conjugation? A) OF factors are transferrable plasmids passed from one cell to another during conjugation. B) O During conjugation, rolling circle replication transfers an F factor from an F+ cell to an F- cell. ) O An F factor acquired during conjugation will automatically be integrated into the recipient's chromosome. D) O Conjugation requires physical contact between cells via the formation of a sex pilus. E) O An Hfr strain is capable of transferring a portion of the chromosome during conjugation.arrow_forwardWhen an E. coli donor cell duplicates a strand of plasmid DNA, and passes this DNA strand to a recipient E. coli cell, without the use of naked DNA in solution or of a viral vector, this is: an example of horizontal gene transfer by means of lysogenic bacteriophages an example of horizontal gene transfer by means of lytic bacteriophages an example of horizontal gene transfer by means of transformation an example of horizontal gene transfer by means of transduction an example of horizontal gene transfer by means of conjugationarrow_forwardIn a P1 transduction experiment, the P1 lysate contains phages thatcarry pieces of the host chromosomal DNA, but the lysate also containsbroken pieces of chromosomal DNA. If a P1 lysate is used to transfer chromosomal DNA to another bacterium, how could you show experimentally that the recombinant bacterium has been transduced (i.e., has taken up a P1 phage with a piece of chromosomal DNA inside) versus transformed (i.e., has taken up a piece of chromosomal DNA that is not within a P1 phage coat)?arrow_forward
- Which of the following is NOT a mechanism by which plasmids inerease the possibility of being present in the new generation of cells? A) O They can be present at a high number so that some copies will end up in each new cell after cell division. B) O They encode traits such as antibiotic resistance that are required for growth in some environments. C) O They cause the cell to replicate much more rapidly than cells that do not have plasmids. D) O They may carry host survival genes and self-preservation genes.arrow_forwardDescribe the mechanisms of horizontal gene transfer in bacteria, describing the manner in which the DNA can be transferred from one cell to another.Choose a disease or an organism that has a well-documented mechanism of resistance (such as methicillin resistant Staphylococcus aureus - MRSA or tuberculosis) and identify the gene or genes that confer resistance and the method of DNA transfer thought to contribute to its spread. This may be from one organism to another or may simply be passed down from mother to daughter cell due to environmental pressure.arrow_forwardTwo mutations that affect plaque morphology in phages (a− and b −) have been isolated. Phages carrying both mutations (a− b−) are mixed with wild-type phages (a+ b+) and added to a culture of bacterial cells. Once the phages have infected and lysed the bacteria, samples of the phage lysate are collected and cultured on plated bacteria. The following numbers of plaques are observed: Plaque phenotype Number a+ b+ 2043 a+ b− 320 a− b+ 357 a− b− 2134 What is the frequency of recombination between the a and b genes?arrow_forward
- You mix two auxotrophic strains of bacteria; one is leu+ trp+ his– met– and the other is leu– trp– his+ met+. After mixing the two strains, you plate the bacteria on minimal medium and observe a few prototrophic colonies (leu+ trp+ his+ met+). To determine whether gene transfer has occurred through conjugation, transformation, or transduction, you design an experiment in which you place filters between the two strains to see if gene transfer occurs. You set up three treatments:-Treatment A No filter, allowing contact between the bacterial strains-Treatment B Filter that blocks cells, but allows viruses and DNA through the filter-Treatment C Filter that blocks cells and viruses, but allows DNA through the filter When you check the results of your experiment, you find prototrophic colonies have occurred following treatments A and B, but not following treatment C. You conclude that gene transfer occurred through... Answer Choices Available: A) Conjugation B) Transformation C)…arrow_forwardFour different types of molecules, namely A, B, C and D were isolated from a primitive life form and studied to determine which of these would have the characteristics of an ancient genetic material. The molecules were incorporated into vectors, which are the phages whose genome were transformed into recombinant DNA. The phages were then made to infect the host bacteria. Transfection with A increased bacterial motility; B resulted in the formation of a pili allowing bacteria to adh to surfaces; causes the overproduction of a membrane protein while D resulted in increased metabolism of the bacterial food source, glucose. Which of the molecules is most likely a genetic material for this primitive life form? А. А В. В С. С D. D E. all of thesearrow_forwardIn Hershey-Chase experiment, bacteriophages protein coats were tagged with radioactive isotope S-32. These phages were used to infect E. coli cells and the cells were further centrifuged to form pellets. Why was the radioactivity level of S-32 found greater outside the cells compared to the E. coli cell pellets? Explain briefly. If the experiment is repeated in the same manner but this time the phage protein coats are labelled with isotope X and the phage DNA with isotope Y, which isotope’s radioactivity will be found in greater amounts in the E. coli cell pellets after centrifugation? Explain briefly.arrow_forward
- By conducting conjugation experiments between Hfr and recipientstrains, Wollman and Jacob mapped the order of many bacterialgenes. Throughout the course of their studies, they identified severaldifferent Hfr strains in which the F-factor DNA had been integratedat different places along the bacterial chromosome. A sample of theirexperimental results is shown in the following table:Explain how these results are consistent with the idea that thebacterial chromosome is circular?arrow_forwardWhich of the following statements is true about a vector?a) Plasmids, phages can be used as vectorsb) All vectors are plasmidsc) Cyanobacteria can also be used as vectorsd) Fungi can also be used as vectorsarrow_forwardIf a single bacteriophage infects one E. coli cell present on a lawn of bacteria and, upon lysis, yields 185 viable viruses, how many phages will exist in a single plaque if 5 more lytic cycles occur? Express your answer using three significant figures (example: 1.11×10^3).arrow_forward
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