Bacteria in the cotton leafworm gut produce the antibiotic mundticin, a peptide that helps protect the insect from virulent pathogens.
Mounting evidence suggests that beneficial gut bacteria can help fight pathogens—just ask anyone who’s successfully tackled a Clostridium difficile infection thanks to a fecal transplant from a healthy donor. However, researchers haven’t had much luck identifying specific species of microbes doing the heroic defense work and the specific molecular weapons they use. That luck could be changing, thanks to a research team led by Wilhelm Boland of the Max Planck Institute for Chemical Ecology and Yongqi Shao of Zhejiang University (Cell Chem. Biol. 2017, DOI: 10.1016/j.chembiol.2016.11.015). The researchers were studying the cotton leafworm, Spodoptera littoralis, a nefarious destroyer of crops in temperate regions worldwide, when they noticed that shortly after caterpillars hatched and started to eat their guts filled with harmful pathogens, including virulent Enterococcus species that can digest the insect from the inside out. The team discovered that with time these bad bacteria were eliminated by an antimicrobial peptide called mundticin produced by another Enterococcus bacterium, E. mundtii. Mundticin is currently being studied as a potential food preservative. The findings support the idea that antimicrobial peptides made by insect gut bacteria might be a source of new antimicrobial food additives or coatings for food contact surfaces, and it lends credence to the hope some researchers have that new antibiotics for humans might be lurking in gut microbiomes of a variety of creatures.