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Thread: Bacteriophages

  1. #1 Bacteriophages 
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    Are bacteriophages harmful to humans?

    and

    What causes a virus to leave the lysogenic phase and go into the lytic phase?


    Whence comes this logic: no evidence = false?

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  3. #2  
    Moderator Moderator AlexP's Avatar
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    I won't guarantee that I'm 100% correct on this, but I'm going to say that bacteriophages are not a danger to humans. I believe viruses recognize specific carbohydrates or whatever on the surface of cells, and these would be found on bacteria, but not on human cells, so the virus wouldn't get the 'ok' to attack the cell.

    As for the second one, what makes a provirus to leave the lysogenic phase and enter the lytic phase is simply some type of stimulus: external stress of some sort, chemical stimulus, whatever. Could be a number of things, but basically it's just some event that triggers it.

    (finally, something that I actually know something about!)


    "There is a kind of lazy pleasure in useless and out-of-the-way erudition." -Jorge Luis Borges
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  4. #3  
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    Simply by definition, no they are not!
    A bacteriophage is a virus that infects bacteria.

    The answer is a complex gene expression shift.
    It is really quite neat.

    For example:
    Lambda (a bacteriophage that infects E. coli) will want to transition from lysogenic to lytic cycle if the bacteria is under stress and is about to die.
    So lamba has a repressor that is cleaved by RecA* ....

    RecA is a protein that binds ssDNA. ssDNA is present in the bacteria in high amounts in times of stress ... RecA* is the resulting nucleoprotein filament.

    So the lamba repressor will be cleaved when the cell is under stress and then the transition to a lytic cycle can occur!
    It is not so much that I have confidence in scientists being right, but that I have so much in nonscientists being wrong. --- Isaac Asimov
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  5. #4  
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    Bacteriophages are indeed not harmful to humans, thats the beauty of 'em.
    I just finished my Bachelor-'thesis' on bacteriophage biocontrol. It's bizarre that it's not commonly used yet, because it has a lot of advantages over antibiotics being used today. But I think Omnilytics Inc. has just brought a product on the market, Agriphage, to combat bacterial spot and bacterial speck in tomatos and peppers. Only, if you go ask John Doe on the street if it's ok to desinfect his food with a 'virus', what would he say you reckon?
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  6. #5  
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    Was it not tried in Russia and then abandoned totally for some reason? Why?
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  7. #6  
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    Indeed, bacteriophage research was promising in the 1920's, but due to irreproducable experiments, and even more so the discovery of antibiotics, the research was abandoned. Except for the Eastern European countries, where due to lack of resources antibiotics wasn't really abundant. If I remember correctly, bacteriophages were sometimes used succesfully, e.g. for treating infections of wounded soldiers, but I think sometimes it went wrong, and people lost faith in the bacteriophage-therapy. Maybe when the Eastern European countries had access to antibiotics, there wasn't any need for bacteriophages any more. It's not untill recently, with the upcoming of multiresistent pathogens, that a 'substitute' for antibiotics is needed. But the complex interactions between the phages and their hosts have still to be researched. I reckon thats what went wrong in the Eastern European countries. The lack of knowledge regarding the interactions between phages, pathogens, humans and beneficial bacteria resulted in failure sometimes, and people lost faith.
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