|
 Curently online :
5 |
|
 Total visitors :
7445758 |
|
|
News Feature: Fighting a fungal scourge
Wednesday, 2019/10/09 | 08:53:40
|
|
Amy McDermott PNAS October 8, 2019 116 (41) 20245-20249
Figure: To fight the deadliest wildlife disease on record, a fungus responsible for the decline or disappearance of hundreds of amphibian species including the Panamanian golden frog, researchers are looking to the bacteria that live on frog skin. Image credit: Flickr/Brian Gratwicke.
Researchers trying to rescue amphibians from a global fungus epidemic are finding that bacteria may be their best allies.
More than a decade ago, amphibian microbial ecologist Reid Harris watched a mother salamander as she marched in a figure-eight pattern through her clutch of soft, jellylike eggs. He knew that her strange walk, rubbing up against her brood, transferred beneficial bacteria from her skin onto the eggs to fight off fungal infection. Then something clicked. Harris wondered if she might also be showing him the solution to a scourge threatening hundreds of other amphibian species around the world.
Then, as now, amphibians were dying in droves. At least one-third of species face extinction, with at least 90 confirmed gone and another 500 in decline (1, 2). The major culprit is the skin disease chytridiomycosis, caused by the waterborne fungus Batrachochytrium dendrobatidis, or Bd for short. Under a microscope, fungal bodies anchor themselves in the translucence of frog skin and often group together to form a collection of small spheres. Chytridiomycosis kills by disrupting ion and fluid transport, eventually stopping the host’s heart (3).
A particularly deadly Bd lineage arose in the Korean peninsula sometime in the last century, the source of a pandemic that fanned out across the world through the global amphibian trade, infecting about 700 species in six global regions over the past five decades (4). Naïve immune systems (mostly those of frogs) couldn’t fight off the highly contagious and aggressive pathogen, and chytridiomycosis spread like a leveling wave, becoming the most devastating wildlife epidemic ever recorded.
The stakes were already high when Harris, now emeritus at James Madison University in Harrisonburg, VA, had his epiphany. He suspected that the salamander mother's protective antifungal bacteria could represent a line of defense against Bd marching right under his nose. There might be many bacteria, for that matter, already living on the backs of frogs, salamanders, newts, and toads able to fight off the fungus, he thought. If those bacterial herds could be managed, like a wildlife park, perhaps amphibian microbiomes could be manipulated to better defend against Bd.
Harris and colleagues set about testing a variety of amphibian skin bacteria to see which inhibited Bd growth (5, 6). In a landmark study published in 2009, the researchers used an antifungal bacteria isolated from salamander skin, Janthinobacterium lividum, known as J. liv for short, to protect mountain yellow-legged frogs from severe chytridiomycosis in lab experiments.
The finding kicked off an ongoing effort by Harris, who is director of disease mitigation for the Amphibian Survival Alliance in London, and others to better understand the relationship between amphibian microbiomes and Bd. Studies in the last 10 years show that Bd can change host bacterial communities, hinting at a possible link between the microbiome and disease. In parallel, researchers have also been searching far and wide for antifungal microbes such as J. liv that can be marshaled to protect wild animals under attack by Bd. They've found thousands of candidates that fight fungi in the lab, but few have been field tested. With some luck, this early work could lead to real solutions to a scourge that has victimized amphibians for years. “The idea,” Harris says, “is to augment anti-Bd bacteria on amphibian skin.”
|
Back
Print
View: 315
|
|
[ Other News ]___________________________________________________
|
(40).png "News Feature: Fighting a fungal scourge")
