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Homework5Solution - It could have been by generalized...

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Biology 214/414 Homework #5 Due 9-25-09 Solution Suppose you are working in a hospital in which there are many species of bacteria present. One species (call it “X”) is non-pathogenic, but is resistant to the antibiotic ampicillin; a second species (call it “Y”) is pathogenic, but until now known to be killed by treatment with ampicillin. The housekeeping protocol in the hospital uses an antiseptic cleaner that lyses (that is, breaks open) X cells, thus killing them, but which does not lyse or otherwise harm Y cells. Recently you start finding Y cells that are resistant to ampicillin. By which mechanism of bacterial recombination do you think this change in Y cells most likely occurred and why? It cannot be by conjugation, as that requires contact between two live cells, particularly the donor cell, which would have to be X in this case, and X is dead.
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Unformatted text preview: It could have been by generalized transduction, providing there were transducing phage growing in at least a subpopulation of the X cells when they were treated with the cleaner, and at least some of the phage were mature, either within an X cell just before lysis or previously released from X cells and on surfaces in the hospital, and the phage were not damaged by the cleaner, and the phage is also able to infect species Y. So while possible, transduction is an unlikely explanation. The most likely explanation seems to be transformation, that when the X cells were lysed, X DNA remained, including fragments carrying the ampicillin resistance gene, and this DNA transformed Y cells, transforming them from ampicillin sensitive to ampicillin resistant....
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