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

众所周知，现代两栖动物的灭绝速度远远超过任何其他种类的脊椎动物，包括哺乳动物和鸟类，近三分之一的两栖动物物种受到威胁。为什么两栖动物会以如此快的速度灭绝，这个问题困扰了科学家们30年。当在中美洲和澳大利亚工作的科学家们注意到两栖动物生物多样性的迅速下降正以波浪般的方式蔓延时，揭开了这个谜团的线索。这些下降模式是由一种新出现的传染病引起的，1997年，研究人员发现一种被称为“壶菌”的真菌病原体是原因，并将其命名为Batrachochytrium dendroatidis （Bd）。从那时起，我们的研究已经确定东南亚是这种两栖动物大流行的摇篮，并绘制了Bd在全球范围内的传播地图。与此同时，除了发现世界上Bd高致病性的地区外，我们还发现了它没有引起任何明显疾病的地方，这就引出了一个问题：为什么？我们越来越多地发现，在未感染的两栖动物中，Bd的入侵、建立和扩增受到栖息在两栖动物皮肤上的微生物群落的强烈影响。正如亚历山大·弗莱明（Alexander Fleming）著名的发现，微生物会以各种各样的策略互相攻击，我们的研究旨在了解这种微生物战如何影响两栖动物群落在感染下存活或死亡。这个问题将通过使用高通量DNA测序技术来解决，利用分子条形码技术来表征世界各地两栖动物的微生物。我们的主要观点是，在感染中幸存下来的两栖动物被细菌和真菌的保护性群落“包裹”了。我们将证明这是否是真的，然后我们将试图识别有毒分子，保护两栖动物免受壶菌的攻击。最后，我们将寻求分离和培养对Bd有保护作用的微生物-有时被称为“益生菌”。在这里，我们将把重点扩展到真菌，因为（正如弗莱明所展示的）它们可以非常有效地保护我们免受入侵生物的侵害。我们已经分离出候选真菌“原真菌”，我们将通过实验来确定它们是否真的能保护两栖动物免受致命的Bd感染；这样的原真菌可以提供急需的生物防治新出现的病原体，如Bd。这最终是我们项目的主要应用目标。

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.