Probiotic could save bats from white-nose syndrome

Since 2006, a fungal disease called white-nose syndrome has caused massive die-offs of bats in eastern North America. Now, scientists from the University of California, Santa Cruz, say that bats may already carry a potential cure for their ills, in the form of bacteria found on their skin.

Lots of evidence has emerged over the last few years suggesting that the microbial communities associated with the human body – in the mouth, the gut, the skin – help keep us healthy and, when they are out of whack, often play a role in disease. It seems this is likely true for wildlife species as well, raising the slightly nutty-sounding but appealing possibility that some wildlife diseases could be treated by manipulating animals’ microbiota.

In the new study, researchers swabbed the forearms and muzzles of bats hibernating in New York and Virginia caves to sample the animals’ naturally occurring skin bacteria. They cultured these bacteria in the lab and tested their activity against the fungus that causes white-nose syndrome, Pseudogymnoascus destructans.

The white-nose fungus colonizes the nose, ear, and wing skin of bats when their body temperature drops during hibernation. Scientists don’t know exactly how the infection kills the animals, but it may cause them to arouse from hibernation more frequently than normal, and thus deplete their energy stores.

Four species of bats have suffered up to 90% population declines in affected regions and one, the northern long-eared bat (Myotis septentrionalis), is in danger of extinction.

Preliminary experiments identified six bacterial isolates from bat skin with some ability to inhibit the growth of white-nose fungus in laboratory dishes, the researchers reported April 8 in PLoS ONE. All belong to the genus Pseudomonas, a widely distributed group of bacteria that are known to have antifungal activity.

The researchers ran more extensive tests on these six isolates, gauging the ability of the bacteria to grow in dishes carpeted with white-nose fungus and, on the flip side, the ability of white-nose fungus to take hold in dishes where bacteria were already growing.

Two isolates emerged as the winners in both challenges. The researchers dubbed them PF1 and PF2 for Pseudomonas fluorescens, the bacterial species that these strains most closely resemble.

A different strain of P. fluorescens is used to fight fungal diseases of crop plants. Even more intriguing, related bacteria produce compounds that inhibit growth of the chytrid fungus linked to recent amphibian population declines.

The top two bacterial isolates found in the new study both came from the big brown bat (Eptesicus fuscus), which has been relatively unscathed by white-nose syndrome. This is a hint that the bats’ natural skin microbiota could afford some protection against white-nose syndrome, and help explain why species differ in vulnerability to the disease. But more research is necessary to confirm this.

Probiotics, meaning beneficial bacteria, have been used in agriculture and aquaculture, but haven’t yet been used against wildlife disease. That may be about to change.

The researchers suspect that among bats in the wild, antifungal strains of bacteria are generally present at too low a concentration on the skin to reliably protect them from the disease. They’re now treating live bats, hibernating in a laboratory setting, with the bacteria to see if this can help them sleep an untroubled winter sleep. – Sarah DeWeerdt | 14 April 2015

Source: Hoyt J.R. et al. 2015 Bacteria isolated from bats inhibit the growth of Pseudogymnoascus destructans, the causative agent of white-nose syndrome. PLoS ONE DOI: 10.137/journal.pone.0121329

Header image: A northern long-eared bat in Illinois affected by white-nose syndrome. Credit: J.R. Hoyt.