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    Post: Science Daily~Scientifically Rethinking Fungi's Abilities

    Posted by Sharon on 3/18/10


    "..this study we found fungi able to transfer an infectious
    capability to a different strain in a single generation,"
    he said. "We've probably underestimated this phenomenon,
    and it indicates that fungal strains may become pathogenic
    faster than we used to think possible."

    "..suggests that fungi have the capacity to rapidly change
    the make-up of their genomes and become infectious to
    plants and possibly animals, including humans."

    "...evolution of virulence in fungal strains that was once
    believed to be slow has now been shown to occur quickly,
    and may force a renewed perspective on how fungi can
    behave, change and transfer infectious abilities."

    ScienceDaily (Mar. 17, 2010) Fungi have significant
    potential for "horizontal" gene transfer, a new study has
    shown, similar to the mechanisms that allow bacteria to
    evolve so quickly, become resistant to antibiotics and
    cause other serious problems.

    This discovery, to be published March 18 in the journal
    Nature, suggests that fungi have the capacity to rapidly
    change the make-up of their genomes and become infectious
    to plants and possibly animals, including humans.

    They are not nearly as confined to the more gradual
    processes of conventional evolution as had been believed,
    scientists say. And this raises issues not only for crop
    agriculture but also human health, because fungi are much
    closer on the "evolutionary tree" to humans than bacteria,
    and consequently fungal diseases are much more difficult to
    treat.

    The genetic mechanisms fungi use to do this are different
    than those often used by bacteria, but the end result can
    be fairly similar. The evolution of virulence in fungal
    strains that was once believed to be slow has now been
    shown to occur quickly, and may force a renewed perspective
    on how fungi can behave, change and transfer infectious
    abilities.

    "Prior to this we've believed that fungi were generally
    confined to vertical gene transfer or conventional
    inheritance, a slower type of genetic change based on the
    interplay of DNA mutation, recombination and the effects of
    selection," said Michael Freitag, an assistant professor of
    biochemistry and biophysics at Oregon State University.

    "But in this study we found fungi able to transfer an
    infectious capability to a different strain in a single
    generation," he said. "We've probably underestimated this
    phenomenon, and it indicates that fungal strains may become
    pathogenic faster than we used to think possible."

    Researchers from the Center for Genome Research and
    Biocomputing at OSU collaborated on this study with a large
    international group of scientists, including principal
    investigators from The Broad Institute in Massachusetts,
    the University of Amsterdam, and the USDA Agricultural
    Research Service at the University of Minnesota.

    Bacteria use "horizontal" genetic transfer through
    chromosomes and DNA plasmids to change quickly, which is
    one reason that antibiotic resistance can often develop.
    This capability was believed to be possible, but rare, in
    fungi. In the new study, based on a genome-wide analysis of
    three Fusarium species, it was shown experimentally that
    complete chromosomes were being transferred between
    different fungal strains, along with the ability to cause
    infection. Various Fusarium fungi can infect both plants
    and humans.

    In humans, fungal infections are less common than those
    caused by bacteria, but can be stubborn and difficult to
    treat -- in part, because fungi are far more closely
    related to animals, including humans, than are bacteria.
    That limits the types of medical treatments that can be
    used against them. Fungal infections are also a serious
    problem in people with compromised immune systems,
    including AIDS patients, and can be fatal.

    According to Freitag, this new understanding of fungal
    genetics and evolution is great news.

    For one thing, it may help researchers to better understand
    the types of fungal strains that are most apt to develop
    resistance to fungicides, and help crop scientists develop
    approaches to minimize that problem.

    Fungal diseases are a major problem in crop agriculture,
    and billions of dollars are spent around the world every
    year to combat new and emerging fungal pathogens in plants,
    animals and humans.

    On a more basic level, this study provides evidence that
    the "tree of life," with one trunk and many branches, is
    outdated. It should be replaced by a "network of life" in
    which many horizontal connections occur between different
    species.


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