Ecological and evolutionary determinants of microbial community composition on the amphibian skin

两栖动物是脊椎动物中濒危物种比例很高的一类，很大程度上是由于新出现的病原体。它们的皮肤也因各种毒素而闻名，这些毒素被认为是作为抗菌防御而进化的，但也可能经历微生物介导的生物转化。尽管与两栖动物皮肤相关的微生物群落对理解生态和进化以及改善两栖动物的保护具有重要意义，但它们的知识却令人惊讶地匮乏。该项目旨在了解两栖动物皮肤中微生物群落的模式，它们的组装过程以及它们对毒素产生的影响。它将结合(i)使用454和Illumina测序对来自德国和马达加斯加的两栖动物样本进行原核生物群落组成筛选，（ii）测试宿主系统发育与栖息地对这些群落的影响，（iii）评估微生物之间的积极和负面物种关联，（iv）监测同一两栖动物标本上的微生物群落动态，以及抗生素治疗后的群落组装。(v)筛选两栖动物大腺体是否存在共生细菌，筛选抗生素治疗前后毒素产生的变化。将对数据进行分析，以检验各种假设，例如，由于大量的抗菌物质，与其他皮肤栖息地相比，两栖动物皮肤上的原核生物群落的多样性较低，这些群落来自环境而不是垂直传播，以及皮肤微生物参与两栖动物毒素的生产和生物转化。

Amphibians are a vertebrate group with a high proportion of species threatened with extinction, to a great part due to emerging pathogens. They are also well-known for the variety of toxins in their skin which are assumed to have evolved as a antimicrobial defense but which might also undergo microbe-mediated biotransformation. Knowledge on the microbial communities associated with the amphibian skin is surprisingly scarce despite their importance to understand ecology and evolution and improve conservation of amphibians. The proposed project aims at understanding the patterns of microbial communities in the amphibian skin, their assembly process, and their influence on toxin production. It will combine (i) screening of prokaryotic community composition using 454 and Illumina sequencing of samples from German and Madagascan amphibians, (ii) testing for host-phylogeny vs. habitat influences on these communities, (iii) assess positive and negative species associations among microbes, (iv) monitor microbe community dynamics on the same amphibian specimen over time, and community assembly after antibiotic treatment, and (v) screen amphibian macroglands for presence of symbiontic bacteria and screen changes in toxin production before and after antibiotic treatment. Data will be analysed to test various hypotheses such as a lower diversity of prokaryotic communities on the amphibian skin compared to other skin habitats due to the large amount of antimicrobial substances, the origin of these communities from the environment rather than vertical transmission, and the involvement of skin microbes in production and biotransformation of amphibian toxins.