The curious case of the bats and bananas

White-nose syndrome is a disease that has devastated bat population in north-eastern United States and the east coast of Canada in the last decade.  It is linked to a fungus (Pseudogymnoascus destructans), and is a horrific disease that affects bats as they roost over winter1.  As well as reducing their immune system, it causes them to come out of hibernation too early. With insufficient insects to prey on in colder weather, this leads to starvation. Mortality rates in some roosts have been over 90%, with six million bats dying since 2006.

Completely unrelated to this, in a bid to prevent fruit rotting before reaching shop shelves, researchers at Georgia State University were investigating the ripening process. Whilst assessing the ability of volatile organic compounds (VOCs) emitted by the bacterium Rhodochrous rhodochrous to delaying ripening in bananas, they noticed that a side-effect was to suppress fungal growth: the fruit were not getting mouldy2.

Having seen pictures of thousands of dead bats in the news, graduate student at Georgia State University, Chris Cornelison made a deductive leap.  In a simple petri dish experiment, the white-nose fungus P. destructans was exposed to the bacterium. This was found to have an antagonistic effect, inhibiting fungal growth3.

Fast forward several months, and trials of R. rhodochrous as a biological control were carried out. In partnership with several organisations, the VOCs from the bacterium were tested on live bats with white-nose syndrome. After treatment and roosting over winter, they had no detectable signs of the disease and could be released.

This is a positive step forward, though further research is needed to develop it into a workable treatment that can be used in the wild.  The aim is to inhibit P. destructans without destroying other harmless fungi, so interactions between the VOCs and many other fungi species need to be tested.  Researchers also need to sure VOCs are not toxic to other organisms living in and around the cave systems, to avoid impacting other parts of the ecosystem.

Whilst the fungus has been found in the UK, it has thankfully not led to white-nose syndrome and the mass mortalities seen across the Atlantic4. Let’s hope this amazing discovery will lead to a cure for our American cousins.

Kate Wright, MSc Biodiversity & Conservation (Year 1)

Photo available under Creative Commons licence, credit US Fish & Wildlife Service
https://www.flickr.com/photos/usfwshq/6847107816/in/photostream/

References:

  1. Volk T, Blehert D, Gargas A, Trest M & Christensen M (2009) “Geomyces destructans, a fungus associated with bat White-Nose Syndrome (WNS)”, Fungi of the Month (Nature Blog) [Online] Available at: http://botit.botany.wisc.edu/toms_fungi/may2009.html (Accessed 2nd November 2015)
  2. Matt Miller (2015) “Bananas to Bats: The Science Behind the First Bats Successfully Treated for White-Nose Syndrome” Cool Green Science (Nature Blog) [Online] Available at: http://blog.nature.org/science/2015/05/27/bananas-to-bats-the-science-behind-the-first-bats-successfully-treated-for-white-nose-syndrome/ (Accessed 2nd November 2015)
  3. Cornelison C T, Keel K et al (2014) “A preliminary report on the contact-independent antagonism of Pseudogymnoascus destructans by Rhodococcus rhodochrous strain DAP96253” BMC Microbiology (Impact Factor: 2.73). 14(1):246, DOI: 10.1186/s12866-014-0246-y
  4. Bat Conservation Trust (2015) “White-nose syndrome” [Online] Available at: http://www.bats.org.uk/pages/about_bats-white-nose_syndrome-586.html (Accessed 2nd November 2015)

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