Fratricide within the Harmony of the Ants’ Fungal Garden

In a shining example of symbiosis, certain ants cultivate coveted fungus and, in return, the fungus provides sustenance to the ants. Unfortunately, like in any garden, pests can be a problem. To help defend against invasive bacteria and fungi, the ants have recruited several additional symbiotic allies, including some champions of antibiotic production: bacteria themselves. In addition to defending the garden, a few of these chosen bacteria appear to have another agenda: to kill off any bacteria who might try to supplant them from their plush symbiotic position.

There are several different, yet closely-related, strains of an actinobacteria called Pseudonocardia that can play equivalent roles as symbiotic partners for the ants. Amongst these, researchers have encountered one strain that decimates even seemingly identical bacteria. It does so by secreting a previously undiscovered antibiotic molecule, which is a more potent version of a naturally occurring bactericidal and anti-tumor molecule called rebeccamycin. When the researchers traced back the source of this new ability, they found that this strain alone had acquired a transmissible ring of DNA, called a plasmid, which contained the blueprint for manufacturing this particular new antibiotic.

While it’s still unclear how this strain acquired the new genetic material, such fungal gardens are proving to be a valuable source of therapeutically interesting molecules.

 

Image courtesy of Alex Wild [CC0], via Wikimedia Commons