Harnessing Bacteria to Prevent the Deaths of Millions of Bats
And we humans depend — really depend — on bats.
Without bats, we’d be in a fine mess.
Every day, our little winged friends rid the world of a colossal amount of crop-destroying insects.
Worryingly, though, bats are being killed off by the millions by a particularly nasty fungus.
The good news, however?
Bacteria may be coming to their (and indirectly, our) rescue.
It’s Bacterium vs. Fungus.
More on this in a moment, but first it may be helpful to understand just how important bats are when it comes to insect control.
You see, during the active season, generally in the warmer months, a bat can consume two-thirds of its body weight in insects every night.
To put that in context, this would be like the average American male scoffing 275 Big Macs a day.
And that’s a lot: in Morgan Spurlock’s Supersize Me, his daily intake was a mere 9.6.
To gain some agricultural perspective, on the first of two occasions we turn to a graduate student.
In 2015, Josiah Maine, a grad student at Southern Illinois University’s Cooperate Wildlife Research Lab, erected enclosures around cornfields that let in insects, but prevented bats from getting in to scavenge.
His experiment measured how corn in the net-covered fields fared compared to unenclosed neighbors and was astonished to discover that there was 50% more fungal growth and crop damage to the enclosed cornfields.
Running some worldwide numbers, researchers estimated that bats save farmers $1 billion a year, on corn alone.
Bats are therefore of huge economic and ecological importance.
It’s heart-breaking to learn, then, that bats across the US are being decimated by a devastating disease known as White-Nose Syndrome (WNS).
Despite its apparently innocuous name, WNS is deadly, having killed more than six million bats since it first arrived in North America in 2006. It now affects half of the 47 species of bats in the US.
The syndrome is caused by a cold-loving fungus named Pseudogymnoascus destructans and originally showed up in upstate New York eleven years ago.
It has already spread to 31 states.
Although the P. destructans fungus is not always visible to the naked eye, it tends to collect as a white deposit on a bat’s nose as well as on other hairless regions of the creature’s body, such as its wings.
WNS leads to bats exhibiting eccentric behavior during the cold winter.
Instead of hibernating safely in caves, they are inclined to fly outside during the daytime and also to congregate around the entrances of their hibernation areas.
This causes them to use twice as much energy as healthy bats, burning the fat they’ve stored for the winter months, and ultimately leading them to starve to death.
In recent years, much has been written about the significance of the loss of honeybees in the US, but while the consequences of the effects of WNS on the bat population could be every bit as catastrophic, the situation seems to have been somewhat under-reported.
And that’s curious, since it has been estimated that the loss of North American bats could cost agriculture almost $23 billion a year.
Overwhelmed by the rapid spread of WNS in the US, bat researchers initially adopted a “try anything” approach, including positioning heaters in caves to prevent growth of the fungus and closing off caves to humans in an effort to stop people bringing in spores.
They even tried spraying spelunkers and cave tourists with antifungal solutions.
None of these methods stopped the onslaught of WNS, however.
But this is where our second grad student comes in, another example of the way in which relatively young minds can sometimes make valuable perceptive leaps.
Chris Cornelison, an applied microbiologist at Georgia State University in Atlanta, took his inspiration from an unusual place.
A bacteria named Rhodococcus rhodochrous (so good, they almost named it twice) is commonly used to slow fruit ripening during its journey from field to supermarket, but one of the grad student’s colleagues discovered that it also inhibited the growth of fungus on bananas.
Chris Cornelison said, “I was standing there looking at a bucket of moldy bananas next to a bucket of bananas with no mold… If the bacterium could be so effective on fungi on bananas, could it have similar effects on fungus on bats?”
His bucket-filled thoughts led to research.
Stunningly successful research, as a matter of fact.
The treatment pioneered by Chris didn’t involve bats being somehow coated with bacteria, since the fungus-inhibiting effects of R. rhodochrous are actually produced by its vapors, known as Volatile Organic Compounds (VOCs).
So Chris put bats in a mesh bag, which was then itself placed in a large cooler for a day or two.
The cooler contained plates of the bacterium, and the VOCs produced by the bacteria spread from the plates to the bats, arresting WNS.
The bacteria do not cure WNS, but they do stop the development of the fungus, inhibiting its growth.
Of course, treating a few bats in a cooler is a long way from tackling huge colonies in caves, but this small experiment was a giant first step.
It’s vital to ensure that introducing the bacterium and its ensuing VOCs doesn’t disrupt the delicate ecology of caves, but researchers are considering adapting nebulizers to pump VOCs into the caves, serving the dual purpose of scaling up the treatment as well as avoiding the need to handle bats, which can adversely affect their health.
It is of course fantastic to come across yet another way in which our friends, the bacteria, continue their good work.
But it’s also brilliant to be once again reminded of the ingenuity of younger minds, in this case connecting moldy bananas to a devastating bat disease.
As Chris Cornelison remarked, “It was one of those leaps of thought in science that maybe only a grad student could make.