"Plant associated microbes have been shown to increase plant growth and production drastically, yet we are just beginning to understand the parameters that impact these interactions. Rhizobia are primary bacterial symbionts of legumes and infect root hairs to form nodules, within which, the symbiotic rhizobia fix atmospheric nitrogen into biologically available forms in exchange for carbon from the host. The aim of this project is to understand the community structure and diversity of the nodule microbiome, with emphasis on the less abundant members, among coexisting clover species. North American clover Trifolium-Rhizobium communities are a good system to study host interactions with microbiomes given the high local species diversity. We analyzed the nodule microbiome of six congeneric clover plants when they were grown in soils conditioned by members of their own species and in soils conditioned by congener species by sequencing the 16s rRNA gene. The visualized microbiomes are similar, with 96% of all reads belonging to the order Rhizobiales. The rest of the OTUs belong to rarer groups of microbes. Further, the structure of the microbiome is impacted by both the host plant species and the soil in which the host is grown in, with soil explaining a larger degree of variation. There also is a strong interaction between soil and host in structuring the microbiome. The results are similar when the microbiome is analyzed with and without its most dominant order (Rhizobiales)."--Page ii.
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