Abstract Detail



Symbioses: Plant, Animal, and Microbe Interactions

Lawrence, Travis [1], Weston, David J. [2], Carrell, Alyssa [3], Gable, Megan [2], Schmutz, Jeremy [4], Healey, Adam [4], Grimwood, Jane [5], Northen, Trent R. [5], Louie, Katherine [5], Anderton, Christopher [5], Velickovic, Dusan [5], Chu, Rosey [5], Pasa-Tolic, Ljiljana [5], Orr, Galya [5], Mitchell, Hugh [5], Markillie, Lye Meng [5].

Characterizing a tripartite plant–fungus–bacteria symbiosis of a peatland ecosystem.

Plant–microbiome systems play critical roles in terrestrial carbon and nitrogen processes. A dramatic example of this principle is provided by ecosystems dominated by the peat moss Sphagnum, which occupy just 3% of the Earth’s land surface yet store approximately 25% of the planet’s soil carbon as dead recalcitrant organic matter (i.e., peat). Sphagnum species are key members of peatland ecosystems, in which they can account for up to 40% of total ecosystem productivity. In addition, together with their associated N2-fixing bacteria, they provide critical nitrogen input to peatland ecosystems. Associations between Sphagnum and phototrophic microorganisms were first reported more than a century ago describing the presence of cyanobacteria within the dead water-filled hyaline cells of plant leaflets. Subsequent studies revealed that several algae/cyanobacterial genera are associated with the outside surfaces of moss plants as epiphytes, whereas Nostoc is the genus most commonly found within plant cells as an endophyte. Cyanobacteria associated with Sphagnum fix nitrogen at higher rates than non-Sphagnum associated cyanobacteria, and when in symbiosis N fixation can occur at low pH values. Additionally, intracellular imaging approaches have revealed that Sphagnum hyaline cells are occupied not only by Nostoc, but also by a diverse array of heterotrophic bacteria and fungi. Furthermore, SEM imaging has shown a potential role of fungi in the Sphagnum-Nostoc symbiosis, revealing that fungal hyphae can enter hyaline cells and envelop the resident cyanobacteria.  Despite the importance of this unique symbiosis to plant growth, ecosystem productivity, and even global carbon and nutrient cycling, we lack a basic understanding of how the symbiosis forms, which metabolites are exchanged, and what role, if any, fungi may play in this tripartite interaction. To address these questions, we used cross-feeding studies and spatially resolved metabolic profiling to determine which metabolites are acquired, competed for, or uniquely exchanged among a constructed Sphagnum, cyanobacterium, and fungus symbiosis. In addition, we used metatranscriptomic and metaproteomic approaches to investigate how symbiosis altered individual species’ physiology.


1 - Oak Ridge National Laboratory, P.O. Box 2008, Bldg. 1507 MS 6407, P.O. Box 2008, Bldg. 1507 MS 6407, Oak Ridge, TN, 37831, United States
2 - Oak Ridge National Laboratory
3 - 1812 Plumb Branch Rd, Knoxville, TN, 37932, United States
4 - HudsonAlpha Institute for Biotechnology
5 - Pacific Northwest National Laboratory

Keywords:
symbiosis
Sphagnum
fungi
Cyanobacteria.

Presentation Type: Oral Paper
Number: 0005
Abstract ID:877
Candidate for Awards:None


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