Bacteriophages and Bacterial Virulence
There's a recent article reporting that the bacteriophage YpfPhi contributes to the pathogenicity of the plague bacillus, Yersinia pestis. Virulence factors carried on phage are quite common. Why should this be? It's an interesting question. I don't think anyone has satisfactorily addressed this problem. For further reading, here's a nice open access review.
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Is it really so puzzling? Virus accidentally acquires virulence gene, virus infects new host, virulence gene boosts host's ability to spread, thereby spreading virus, etc.
ReplyDeleteWell nice scenario, except that it is not certain that increasing virulence increases the host's ability to spread. In fact, increased virulence often has the direct opposite effect (i.e. killing bacterial hosts before they can spread the bacterium). If the bacteria really benefit from the deal, then I expect that their own genomes would encode these virulence factors and cut out the middlemen (i.e. phage). I suspect the situation is more complex, and that the virulence gene itself is enhancing its own fitness at the expense of other genes.
ReplyDeleteGood point. On the other hand, some so-called virulence genes are turning up in perfectly harmless commensals, so things may be even more complex.
ReplyDeleteHi John: Since you're the only phage biologist I "know", let me ask you something. The FDA has recently approved Listex p100 as an additive to deli meats and cheeses. This is a lytic phage which is shown to attack only Listeria. My concern is that it may also infect normal intestinal flora. What do you think?
ReplyDeleteThanks, SG
SG: One of the advantages of phage antibacterial treatment is that phages are highly specific for their intended targets. Most phages bind to specific exterior receptors to gain entry to host cells.
ReplyDeleteCompare this to the activity of antibiotics, some of which, for example, interfere with host cell wall construction, and thus cannot discriminate "good" from "bad" bacteria.
I posted about Intralytix, a phage therapy company, earlier this year.
http://evilutionarybiologist.blogspot.com/2007/04/applied-phage-biology.html
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