Field grown Populus harbor a diverse consortium of microbes. To gain insight into the functional role of these microbial members on the Populus host, we isolated over 3,200 strain bacterial strains using a direct plating approach. Our prior studies used this collection with individual strain and very reduced community (< 10 members) assays to evaluate questions pertaining to plant – microbe interactions. However, such studies have little relevance to boarder community-based questions, such as the rules governing community assembly and the relationship between diversity and function. To address this limitation, we created a synthetic community approach that distinguishes the genetic diversity of genome sequenced strains using Illumina 16S rRNA sequencing. We are now using this approach to inoculate germ-free Populus trichocarpa with relatively large bacterial communities to determine how host plant genetics and nutrients interact to shape the associated community, and in turn, how that specific community influences plant nutrient status.
Results/Conclusions
To create the synthetic community, all 16S rRNA sequences from the sequenced bacterial strains within the culture collection were extracted, trimmed to the specific Illumina region and aligned using a custom computational workflow. Our workflow was scripted to design a community that had at least three nucleotide differences within the 16S rRNA region. This resulted in a community consisting of 154 members that spans substantial genetic diversity including 4 phyla, 9 classes, 12 orders, 32 families and 77 genera. Many strains contain potentially beneficial functions for the host including nitrogenase activity, indole-3-acetic acid production and anti-microbial production. Initial experiments with reduced ten-member communities have shown that community assembly is surprisingly reproducibly, and that specific community members impact host plant nitrogen status. Our current experiments are investigating whether these findings are observed within much larger communities.