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Thread: Phages and bacteria?

  1. #1 Phages and bacteria? 
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    I know that for a while now scientists have been researching the use of bacteriophages to attack bacteria.

    Yet, in some bacteria such as E. coli (I think, correct me if I'm wrong), when the phage incorporates it's genetic material into the bacteria, the otherwise non-virulent pathogen becomes virulent.

    So, I was wondering if it would be possible to attack this bacteria if we could induce the virus into entering the lytic cycle? Is there even a way that would be safe in humans?


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  3. #2  
    Forum Cosmic Wizard paralith's Avatar
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    By "becomes virulent," I assume you means "becomes pathenogenic for humans." Obviously it's already virulent when it comes to bacteria.

    Viruses evolve to target specific hosts, which is why bacteriophages are an attractive idea - they only target bacterial cells. The cellular surface molecule they recognize and attach to is only produced by certain species - and not produced by human cells. If the virus can't attach to the cell, it can't enter it and eventually destroy it. Now if that changes, as you mentioned, then yes the virus can potentially become dangerous for people.

    I'm not sure I understand your question - you seem to be asking if we can induce the a bacteriophage to do something that certain species of bacteriophage would do naturally on their own. Not all viruses are lysogenic - they don't all incorporate into their hosts' genome. Many of them operate through the lytic cycle alone. At this point it's more a matter of finding the right species than it is to induce it to do anything.


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  4. #3  
    WYSIWYG Moderator marnixR's Avatar
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    i think what he means is that from time to time DNA from the phage can get incorporated in the bacterial DNA, thereby changing the latter's characteristics
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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  5. #4  
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    Quote Originally Posted by marnixR
    i think what he means is that from time to time DNA from the phage can get incorporated in the bacterial DNA, thereby changing the latter's characteristics
    Ohhh - changes the host bacteria. I see.
    Man can will nothing unless he has first understood that he must count on no one but himself; that he is alone, abandoned on earth in the midst of his infinite responsibilities, without help, with no other aim than the one he sets himself, with no other destiny than the one he forges for himself on this earth.
    ~Jean-Paul Sartre
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  6. #5 Use of phage in bacterial infection 
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    Phage was tried in the past but seemed, as many drugs also, to work in vitro but poorly in vivo. This may be due to several factors. For example the phage may not have access to the bacterial colonies of an infection or infective bacteria may change inside a host so that lysis of cells may not be virulent in tissues. Bacteria grow much more slowly in tissues and there are other changes and other genes that become activated during infection. Or, innate defenses of the sick host may attack the phage itself.

    I don't think lysogeny is a reason for the inability of phage to be effective in countering infection. Many strains of bacteria are not lysogenic for infective phage and lysogenic strains have to be selected for in media before a culture of them can be grown.

    Eddie
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