Researchers solved the structure of a bacterial toxin bound to a neutralizing protein, revealing two distinct mechanisms for how the toxin-producing bacteria avoid poisoning themselves.
Microbial communities are of fundamental importance to virtually all natural ecosystems, from the ocean floor to the gastrointestinal tract. Although the term “communities” implies cooperation, scientists now realize that bacterial colonies compete with each other for life-sustaining resources, availing themselves of a variety of strategies to reduce overcrowding. In some cases, they secrete toxins in their fight for survival. Here, researchers studied one such toxin from the bacterium Serratia proteamaculans, various strains of which live inside tree roots or inhabit the digestive tracts of insects and other animals.
Toxin targets cell division
The researchers showed that the toxin, Tre1, targets a bacterial protein, FtsZ, which is analogous to tubulin in human cells. Tubulin molecules are the building blocks of microtubules—long polymers that provide structure and shape to our cells and play an important role in cell division. In bacteria, FtsZ loses the ability to polymerize when attacked by the Tre1 toxin. Instead of dividing, the intoxicated cells grow longer and longer until they eventually split open and die (cellular elongation and lysis).
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Image: Healthy bacteria (left) and bacteria (right) whose cell-division machinery has been disrupted by a toxin newly discovered in some bacterial arsenals.
Credit: Mougous Lab