Testing the role of microbial distribution and functional traits in the ecology and evolution of symbiosis

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All large hosts, including seaweeds, plants, and animals are colonized by microbial symbionts, and these symbionts collectively make up a huge portion of biodiversity. Symbionts contribute to host metabolism, defend against pathogens, and even change the way hosts grow and develop. Symbionts can have positive, negative, or neutral interactions with the host, and these outcomes often depend on environmental context. There can be many symbionts that play critical roles in the health and biology of a given host species over time and across populations. Functions are maintained amidst this rotating cast of symbionts by functional redundancy: many microbes can fulfill a functional role. We know that symbiont communities are influenced by the environment and will change with ongoing environmental change. But we cannot predict what altered communities will look like, or the consequences to their hosts. The proposed research seeks to fill in this knowledge gap. In order to tackle this overarching question, we need a better understanding of symbiont distributions, the factors that cause microbes to associate with hosts, the stability of symbiotic relationships over time, and the relationship between symbiont distribution and function. My group will achieve these goals by: 1. Mapping the distribution of seaweed symbionts, and their functions, across environments to determine host specificity. 2. Develop sugar kelp into a model system for studying symbiosis in the lab. We will develop a library of cultured isolates of microbes, including microbes from general marine environments and those specific to sugar kelp. We will test the hypothesis that specific symbionts play larger functional roles in host biology. This system also enables testing hypotheses on function and/or environmental influence that arise from the other objectives. 3. We will investigate the stability of symbionts and their functions in the face of changing environmental conditions at both the population and individual level. The proposed work will also contribute to the training of 16 HQP from diverse backgrounds. The proposed work contributes to our knowledge of microbial diversity in general and the factors that shape microbial communities.  Understanding the factors that structure symbiont communities will enable fields ranging from human health, to agriculture and aquaculture to develop tools harnessing the power of the microbiome, and in addition to shedding light on the natural history of this vast part of our biosphere.