Peptides

Frog Skin Fights Bacteria
by Emily Hoffman

If thoughts of frogs conjure up images of slime and muck, you may have to change your thinking. Previously undiscovered compounds on the skins of frogs can kill a wide range of bacteria in the lab, a group of researchers have found. These new compounds, small proteins called peptides, were found to be effective against Staphylococcus, certain strains of E. coli and the yeast that causes the fungal infection thrush. The study has been accepted for publication in the journal Peptides.

What led researchers to frogs? "It was serendipitous," says J. Michael Conlon, professor of biochemistry at Nebraska's Creighton University and head of the study. Since it's believed that frogs have a defense against mammalian predators - exploding in the stomach of the animal that consumes it, making it extremely ill - Conlon thought frog skins might contain other defenses too. "We extracted skins ... and looked to see if there were compounds defending against bacteria," says Conlon. And they found many, on frogs such as the Korean frog (Rana rugosa), Japanese frog (Rana brevipoda porsa), European frog (Rana esculenta) and the American Bullfrog (Rana catesbeiana).

With over 3,500 species of frogs, and only 10 or 15 studied thus far, hopes are high that numerous different antimicrobial agents will be discovered. According to experts, with antibiotic resistant strains of bacteria on the rise, it's important that new disease-fighting medicines be developed. "It was thought, ten years ago, that the battle against infectious diseases had been won, that infectious bacteria were on the way out. It's known now that that was far too optimistic," Conlon says. "Bacteria are always evolving ways of getting around antibiotics," says Gerald V. Stokes, acting chair of microbiology at George Washington University in Maryland. "So the pharmaceutical companies and researchers have to try and figure out new types of antibiotics to anticipate these changes."

"Because these are a new class of peptide, potentially they're something bacteria have never seen before, and so it may take them a much, much longer time to evolve resistance," says Stokes. The researchers at Creighton aren't stopping with frogs. "We're using nature as a basis from which we can design new drugs," says Conlon. "We'll try to make (the frog skins) more potent. To maybe target different microorganisms, like TB or the organism that causes strep throat."