Oozing through moist soil and leaf litter, the amoeba Dictyostelium discoideum (better known as the slime mold) kills bacteria, primarily yeast, to extract its nutrients and replicate. The amoeba can even farm bacteria to prevent starvation or to “save them” for later generations. And in addition to providing nutrients, these bacteria can become the amoeba’s army and protect them against environmental toxins.
However, in a recent study published in the Proceedings of Natural Academy of Sciences, scientists have found that the D. discoideum is not unbeatable. The research team found that two different species of bacteria can team up to become a lethal meal for D. discoideum, poisoning and killing the slime mold in the process. One their own, these two bacteria cannot defend themselves against D. discoideum. But together, they "cook up” a highly toxic poison to defeat their common enemy.
The researchers revealed that only one of the bacteria, a type of Pseudomonas, could produce syringafactin, a key component that its partner, a type of Paenibacillus, uses to make the deadly concoction. Syringafactin, is formed on the outside of the bacterial cell and is not itself toxic to the slime mold. But when Paenibacillus is around, it carves the syringafactin into highly poisonous pieces that ultimately kill D. discoideum.
“The cleavage products not only affected the lab strains of amoeba but also wild type [or naturally occurring] strains making this a broad spectrum defense strategy,” said Somak Chowdhury, member of the research team, in a Twitter post about these findings.
This cooperative bacterial interaction provides a clear example of a community-level defense-mechanism type against predators. Whoa!