The Sphagnum – microbiome: insights from field manipulations and synthetic communities
D. WESTON (1), A. Carrell (2) (1) Oak Ridge National Lab, U.S.A.; (2) Duke University, U.S.A.

Justification: Peatland ecosystems are estimated to store a third of stored terrestrial carbon as dead organic peat. The moss plant Sphagnum is a keystone genus in these ecosystems, with its biological function and abiotic environment influencing ecosystem structure and function and potentially global C cycling. These nitrogen limiting peatland systems highlight an important association of Sphagnum plants with N2-fixing (diazotrophic) bacterial associates. Questions: Our research in this area is guided by multiple questions including, who are the diazotrophic members of the Sphagnum microbiome? Does host carbon limitation influence diazotroph interaction? Results: With 16S rRNA profiling of experimentally warmed Sphagnum, we found all samples to be dominated by Alphaproteobacteria (45-51%) followed by Acidobacteria (11-16%) and Gammaproteobacteria (8-9%). We found functional member abundance to vary by warming treatment: diazotroph abundance decreased with increased temperature (6% in ambient control, 3% in ambient +6C) and methanotroph abundance increased with temperature (0.14% in ambient control, 1.3% in ambient +6C respectively). Guided by community profiling results, a diazotrophic bacterium (cyanobacterium) and a fungal isolate (Trizodia spp.) were chosen and used to establish simplified constructed communities under gnotobiotic microcosm conditions. Initial results show that all three members can interact within the same space without observed negative consequences. Current experiments are exploring how increased temperature influences abundance, N2 – fixation and net photosynthesis. Significance: A current collaboration with the DOE Joint Genome Institute has now expanded the genomic resources for this project by providing two draft genomes for S. fallax and S. magellanicum and the resequencing of a 200 individual S. fallax pedigree. Together with isolated fungal and bacterial strains, this represents a tremendous resource to the phytobiome community.

Abstract Number: P5-131
Session Type: Poster