• How stress hormones guide bacteria in th

    From ScienceDaily@1:317/3 to All on Mon Mar 7 21:30:48 2022
    How stress hormones guide bacteria in their host

    Date:
    March 7, 2022
    Source:
    Ludwig-Maximilians-Universita"t Mu"nchen
    Summary:
    A newly discovered protein helps bacteria recognize stress hormones
    in the human body and direct their motion in the host.



    FULL STORY ==========================================================================
    A newly discovered protein helps bacteria recognize stress hormones in
    the human body and direct their motion in the host.


    ==========================================================================
    In humans and animals, catecholamines such as epinephrine, norepinephrine,
    and dopamine are common stress hormones. Stress can increase the body's susceptibility to bacterial infections. In the laboratory, stress
    hormones stimulate the growth of various pathogens. This had already
    been observed in Salmonella (Salmonella enterica serovar Typhimurium),
    and other intestinal bacteria, Escherichia coli and the causative agent
    of cholera, Vibrio cholerae.

    Furthermore, epinephrine and norepinephrine make it easier for bacteria
    to infect the body's cells. And these hormones also influence the
    biosynthesis of virulence factors, which enable pathogens to adhere to, penetrate, and destroy cells.

    "We therefore suspected that some bacteria use such hormones as signals
    to recognize the eukaryotic host environment," says LMU microbiologist Professor Kirsten Jung. "But the molecular basis was not known." Together
    with Professor Stephan A. Sieber from the Technical University of Munich
    (TUM) and other researchers, Jung has now identified the binding site
    of epinephrine and the epinephrine derivative phenylephrine in the
    bacterium Vibrio campbellii. As the team reports in PNAS, the target
    of both molecules is the protein CheW. "The biological significance of
    the mechanism is that bacteria recognize, for example, that they are no
    longer in sea water, but in the intestine of a host," explains Jung.

    Studies with the model organism V. campbellii "We wanted to know how
    bacteria recognize catecholamines as signaling molecules," says the
    LMU scientist. "Which receptors control this process?" Her experiments consisted of several individual steps.

    For the study, Sieber developed a method for chemically modifying
    epinephrine and phenylephrine, so that the researchers could directly
    isolate complexes from the catecholamines and the bound bacterial
    proteins. A prerequisite of the experiments was that the new compounds
    would not have any biological characteristics that the unmodified
    molecules did not have. Jung's group did laboratory experiments to
    demonstrate this was so. Epinephrine binds iron, whereas the epinephrine derivative phenylephrine does not. With their choice of compounds, the researchers wanted to rule out effects that arise when the bacteria have
    a better supply of iron.

    Jung and Sieber worked with Vibrio campbellii as a model organism. The
    marine bacterium infects fish, shrimp, squid, and many other marine invertebrates.

    They added Vibrio campbellii to the chemically modified catecholamines
    and lysed the cells. Next, they extracted from the lysate all proteins
    to which a molecule had bound and characterized them by using proteome analysis. This resulted in a particular enrichment of the soluble
    chemotaxis protein CheW.

    Subsequently, Jung's group isolated the CheW protein directly
    from bacteria, purified it, and measured its binding affinity to catecholamines. In the process, the researchers discovered something surprising: the hormones do not bind to the chemoreceptors themselves,
    as originally expected, but to the coupling protein CheW, which is
    located between receptors and a signal transduction cascade. This entire stimulus perception system controls the motion of the bacterium in a
    chemical gradient.

    "Our study provides new insights into the communication of bacteria with
    their host," summarizes Jung. "We were able to show that the swimming
    behavior of bacteria is modified by host hormones, which is controlled
    by CheW." Motility, and in particular directed motility, is decisively important for host colonization, as bacteria deliberately seek to colonize
    an organism and conquer all niches. In the next step, Jung now wants to
    find out whether the same mechanism can be detected in other bacteria.

    ========================================================================== Story Source: Materials provided by
    Ludwig-Maximilians-Universita"t_Mu"nchen. Note: Content may be edited
    for style and length.


    ========================================================================== Journal Reference:
    1. Angela Weigert Mun~oz, Elisabeth Hoyer, Kilian Schumacher, Marianne
    Grognot, Katja M. Taute, Stephan M. Hacker, Stephan A. Sieber,
    Kirsten Jung. Eukaryotic catecholamine hormones influence the
    chemotactic control of Vibrio campbellii by binding to the coupling
    protein CheW. Proceedings of the National Academy of Sciences,
    2022; 119 (10) DOI: 10.1073/ pnas.2118227119 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220307113056.htm

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