The microbiome of plants plays a key role in the health and survival of its host. Host plants can benefit through activities, such as, the production of growth promoting hormones, phosphorus acquisition, nitrogen fixation and protection against pathogens. Through the activities of the microbiome plants are able to flourish in harsh environments with limited resources.
Pinus flexilis is a high elevation conifer species that grows in nutrient poor environments across the western United States. Previous work on P. flexilis foliar tissue from two sites (Colorado and California) have shown a simple and consistent bacterial community dominated potential nitrogen fixing bacteria in the family Acetobacteraceae. In this study we ask if the core community previously documented in P. flexilis is consistent across its entire native range.
Needle samples from 10 P. flexilis trees were sampled from 15 sites across the native P. flexilis range. Sonication was used to separate bacterial communities from the needle surface and endsphere compartments. DNA was extracted from both compartments and used as a template to amplify the 16S rRNA gene. Samples were sequenced on the Illumina HiSeq platform using a dual indexing approach. Sequences were processed through the Qiime2 bioinformatics pipeline using the DADA2 package to infer amplicon sequence variants.
Results/Conclusions
Preliminary results suggest that both needle surface and interior communities are primarily comprised of Proteobacteria, specifically Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria, but that the two compartments host different proportions of each. Surface communities had a greater proportion of Alphaproteobacteria comprised mainly of a single family the Acetobacteraceae. The endosphere compartment had a greater proportion of Gammaproteobacteria from the family Pseudomonadaceae. Our results also suggest that geography structures the P. flexilis foliar microbiome.
The core of Acetobacteraceae that was previously seen in P. flexilis was also found in these samples but within the surface communities instead of the endosphere communities. The endosphere communities were dominated by Pseudomonadaceae which have been found to rapidly colonize root tissue in other plant systems. Some strains of Pseudomonadaceae are also capable of nitrogen fixation,and may be responsible for the nitrogenase activity previously documented in the foliar tissues of P. flexilis.