Researchers were able to show which mechanisms Salmonella use to transport toxins into the cells Berlin – Bacteria can move to food sources and away from pollutants. In technical jargon, this “motor” is referred to as a flagellum. “This complex organism of movement is made up of several thousand individual subunits that have to fit together meaningfully,” explains Marc Erhardt from the Humboldt University in Berlin. Flagella also play a role in pathogens. With their help, they reach the infection site, colonize the host and form stable biofilms. Marc Erhardt and his research team have now used genetic, biochemical and microscopic methods to study the bacterium Salmonella enterica, which can cause life-threatening food poisoning. The result: Salmonella move with the help of flagella to the intestinal cells and injected with a kind of injection system toxins. This injection system uses a similar protein pump for building up as the flagellum: the type III secretion system. Injection system of bacteria Already from previous investigations it is known which energy source uses this secretion system. The beginning is a protein anchor in the membrane, which then like a pump, the other components from the cell. These flagellin building blocks sort themselves into a long chain, the flagellum. These flagella can be up to ten times longer than the bacterial cell. With fluorescence dyes, the scientists from the Humboldt University were able to mark the structure in stages. “The flagella grow slower over time,” says study leader Erhardt, “because the building blocks have to travel an ever longer distance to the end.” This may also be relevant because this process may also apply to the injection systems of pathogens that cause bacteria to carry toxins into cells. The conclusion of the researchers: These “syringes” have developed from the flagellar systems. The researchers were now able to identify the roles of two involved proteins: “FliP builds the pore, and FliO is the organizer, who ensures that the pore proteins correctly store together,” explains Erhardt. They are therefore potential starting points for drugs: “An active ingredient that prevents pore formation would be a double success: it would affect bacteria that produce flagella, as well as those that use molecular spraying,” says Marc Erhardt. (red, 16.4.2018)
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