Since it first emerged in New York in 2006, the fungal pathogen Pseudogymnoascus destructans, which causes white-nose syndrome, has devastated bat populations throughout the eastern half of the continent. At least four species are heading toward extinction, suffering declines in certain regional populations of over 90%. Researchers hoping to reduce the impacts of the disease are turning to beneficial bacteria. Two teams working with two types of bacteria – one living on bats and one living in soil – are seeing some very promising starts, Nature reports.
Cold-loving P. destructans penetrates bat dermal tissue (the nose, ears, and wings), and it disrupts processes like heat and water loss, electrolyte balance, and hibernation. Its optimal growing temperature is between 10 and 14 degrees Celsius – right about the same temperature of hibernating bats. As the fungal pathogen repeatedly rouses hibernating bats, their fat stores are depleted too early and the bats starve. Those who survive the infection, which typically lasts 70 to 120 days, are able to clear their bodies of it during the spring. But even though they're fully recovered, these bats are reinfected in the fall. The fungus sticks around on cave and mine walls, persisting for a long time even in the absence of bats.
A University of California Santa Cruz team led by Joseph Hoyt wanted to see if probiotics that naturally occur on bats could inhibit the growth of P. destructans. They isolated six types of Pseudomonas bacteria from the skin of four bat species in New York and Virginia, then cultured them with the fungal pathogen. All of the isolates significantly inhibited the growth of the killer fungus.
The results of the lab study were published earlier this year in PLoS ONE. “We are analyzing data from tests on live bats now, and if the results are positive, the next step would be a small field trial,” Hoyt says in a statement.
Little brown bat with visible symptoms typical of white-nose syndrome in Hardin County, Illinois. Steve Taylor/USFWS Flickr CC BY 2.0
Meanwhile, U.S. Forest Service researchers and Georgia State University’s Chris Cornelison are “treating” infected bats with a soil bacteria called Rhodococcus rhodochrous. These produce natural volatiles that prevent the fungal spores from growing on fruits and crops. “If it can prevent fungi from growing on a piece of fruit,” Cornelison thought, according to Wired, “it might help prevent fungi from growing on a bat.” After capturing infected bats, the team exposed them to the bacteria for 48 hours before releasing them back into their caves to finish hibernating. Most of the treated bats in this field experiment survived the winter.
Then, on May 20, outside the Mark Twain Cave Complex in Hannibal, Missouri, the researchers released many of the bats who had successfully recovered from white-nose syndrome into the wild. The team is currently analyzing their data.
However, even if any of these bacterial treatments are effective, Nature reports, they’ll only be short-term solutions. The bats don’t seem to be developing immunity to the fungus and they might need to be treated every year.