A frog in Brazil's rainforest survives the fungus killing amphibians worldwide not through its own immune system, but through the specific bacteria living on its skin.
Frogs have no scales to hide behind, and their skin stays wet. That is exactly where a fungus called Bd goes to work: it colonizes the skin and eventually stops the frog's heart, and it has already driven dozens of amphibian species extinct worldwide.
Yet some frogs tolerate it. In Brazil's rainforest, the big-headed frog keels over at a touch while the clay robber frog, living in the same place, almost never gets infected.
Wash off the bacteria and it dies
Researchers collected 40 of each species near São Paulo and brought them back to the lab. Half were exposed to the fungus, half were not. Within each group, half got antibiotic baths first that stripped their skin bacteria.
The result was blunt: clay robber frogs exposed to the fungus survived fine, but those given antibiotics first crashed. Big-headed frogs failed either way.
So the clay robber frog's armor is not its own. The bacteria on its skin are what hold the fungus off. The team also isolated roughly 700 bacterial strains from frog skin, tested each one's ability to suppress the fungus, and built the results into a searchable database.
In other words, they are taking inventory of which frogs are carrying the right equipment.
Why it matters
Antibiotics do not just kill germs; they can strip away the defense line an animal depends on. That reframes what 'sterilizing' means: the bacteria on skin are not dirt, they are sometimes a host's only armor, and wiping them out indiscriminately can bring down the very species that was holding its own.
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