Understanding links between microbial communities and emerging fungal pathogens in complex ecosystem

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Modern-day amphibians are known to be suffering rates of extinction that far exceed any other class of vertebrates, including those experienced by mammals and birds, and nearly one third of amphibian species are threatened. The question of why amphibians are going extinct at these accelerated rates has puzzled scientists for three decades. A clue to the mystery came about when scientists working in Central America and Australia noted that the rapid declines in amphibian biodiversity were spreading in a wave-like manner. These patterns of decline were caused by an emerging infectious disease and in 1997 researchers discovered that a fungal pathogen, called a 'chytrid', was the cause, naming it Batrachochytrium dendrobatidis (Bd). Since then, our research has identified South East Asia as the cradle of this amphibian pandemic, and has mapped the spread of Bd worldwide At the same time, alongside finding regions of the world where Bd is highly pathogenic, we have also discovered places where it is not causing any obvious disease which begs the question Why?Increasingly, we find that the invasion, establishment and amplification of Bd in uninfected amphibians is strongly influence by the microbial communities that are found inhabiting the skins of amphibians. As Alexander Fleming famously discovered, microbes predate and attack one another with a diverse array of strategies and our research seeks to understand how this microbial warfare influences whether an amphibian community survives, or succumbs, to its infection. This question will be addressed by using high-throughput DNA sequencing technologies to characterise the microbes on amphibians around the world using molecular barcoding techniques. Our main idea is that the amphibians that survive infection infection are 'clothed' by a protective community of bacteria and fungi. We will show whether this it true, then will attempt to identify the toxic molecules that are protecting the amphibians from their chytrid onslaught.Finally, we will seek to isolate and grow microbes that are protective against Bd - sometimes called 'probiotics'. Here, we will extend our focus to include fungi because (and as Fleming showed) they can be very potent protectors against invasive organisms. We already have isolated candidate fungal 'promycotics', and we will use experiments to determine whether they do in fact protect amphibians against lethal infection by Bd; such promycotics may then offer a much-needed biocontrol against emerging pathogens such as Bd. This, ultimately, is the major applied goal of our project.