• The microbiome: Battle of the bugs

    From ScienceDaily@1:317/3 to All on Tue Oct 5 21:30:40 2021
    The microbiome: Battle of the bugs

    Date:
    October 5, 2021
    Source:
    Ludwig-Maximilians-Universita"t Mu"nchen
    Summary:
    Scientists have shown that, depending on the composition of the
    microbiome, E. coli bacteria can prevent infections by Salmonella
    strains.



    FULL STORY ==========================================================================
    In a new study, Ba"rbel Stecher and her team from LMU have shown that, depending on the composition of the microbiome, E. coli bacteria can
    prevent infections by Salmonella strains.


    ========================================================================== Every individual harbors a specific microbiome, which is unlike that of
    any other. Each is made up of diverse bacterial, fungal and viral species, which are found on all body surfaces -- the skin, mucous membranes and particularly in the gastrointestinal tract. Moreover, the microbiome
    have an enormous influence on the immune system, the endocrine system
    and the metabolism of their hosts.

    Ba"rbel Stecher is Professor of Medical Microbiology and Hygiene in the
    Max von Pettenkofer-Institute at LMU Munich and a member of the German
    Center for Infection Research (DZIF). Her research focuses on the role
    of the gut microbiome in the control of infections. In her latest study
    -- whose first author is doctoral student Claudia Eberl -- her team set
    out to define what a healthy microbiome needs to effectively defeat an
    invasive pathogen. In this case, they asked whether the bacterial species Escherichia coli(E. coli) can provide protection against infection with
    human pathogenic Salmonella species.

    Many people are acquainted with the negative side of E. coli, as specific strains of the bacterium can cause diseases such as diarrhea, sepsis and
    even cancer. But there are lots of benign strains of E. coli. Most of
    these colonize individuals during or soon after birth, and contribute
    to the establishment of a balanced host-microbial interaction. Stecher
    and her research group have now investigated how these strains protect
    their hosts against infection by Salmonella.

    The importance of cooperation It turns out that the critical factor
    is interspecies competition for resources. "We discovered that, in
    particular, competition for a variety of sugars in the gastrointestinal
    tract can account for the failure of Salmonella to colonize the gut,"
    Stecher explains. In order to cause an infection, pathogenic bacteria
    must find an appropriate niche within the gut, which provides them
    with the carbon sources -- such as certain sugars -- that they need
    to replicate. However, competition for carbon sources in the gut
    is fierce. "If commensal E. coli consume all the sugar substrates,
    leaving nothing behind for Salmonella, the risk of infection is strongly decreased," says Stecher.

    However, in order to effectively exclude Salmonella, E. coli usually
    needs help. The new study also shows that E. coli is not always in a
    position to prevent infections caused by Salmonella. "If the complexity
    of the microbiome is too low, its members cannot consume all of the
    sugar substrates thatSalmonellastrains depend on, and this opens up opportunities for the pathogen to become established." Stecher and her colleagues therefore concluded that E. coli needs allies. -- And they
    went on to identify these as species of the Lachnospiraceae. This group
    of anaerobic bacteria is also often found in the human gut, and its
    members can also metabolize various sugars.

    The research strategy "Using synthetic bacterial consortia, we were able
    to construct a model microbiome," Stecher explains. This microbiome was
    made up of 12 bacterial species, all of which are found in the healthy
    murine gut. This combination of species was then introduced into germ-free mice, which were subsequently infected with Salmonella. They discovered
    that, in the absence of Lachnospiraceae, E. coli was unable to prevent Salmonella infection. "This strengthens our conclusion that a combination
    of competition for carbon sources and complex interactions between
    bacterial species can protect the host against bacterial infections,"
    says Stecher.

    To translate these findings to humans, Ba"rbel Stecher plans to work
    with bacterial consortia found in the human gut microbiome. "At some
    point, our work could then help to develop treatments, such as probiotic bacterial cocktails that support the maintenance of a healthy microbiome." ========================================================================== Story Source: Materials provided by
    Ludwig-Maximilians-Universita"t_Mu"nchen. Note: Content may be edited
    for style and length.


    ========================================================================== Journal Reference:
    1. Claudia Eberl, Anna S. Weiss, Lara M. Jochum, Abilash Chakravarthy
    Durai
    Raj, Diana Ring, Saib Hussain, Simone Herp, Chen Meng, Karin
    Kleigrewe, Michael Gigl, Marijana Basic, Ba"rbel Stecher. E. coli
    enhance colonization resistance against Salmonella Typhimurium
    by competing for galactitol, a context-dependent limiting carbon
    source. Cell Host & Microbe, 2021; DOI: 10.1016/j.chom.2021.09.004 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2021/10/211005101834.htm

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