Abstract
dc:description.abstractAlthough occupying just 3 % of Earth’s land surface, peatlands hold roughly a quarter of the planet’s soil organic carbon stock. More than half of this peat consists of undecomposed Sphagnum moss cell wall materials, prompting the proposal that this genus sequesters more carbon than any other plant. The extraordinary recalcitrance of Sphagnum’s cell wall is central both to the long term persistence of this carbon store and its capacity to moderate atmospheric CO₂. Despite decades of study, the molecular basis of Sphagnum’s exceptional decay resistance remains unresolved and a subject of active debate. To address this, this study aimed to investigate the composition and structural organisation of Sphagnum’s cell wall and to examine how cell wall features may influence Sphagnum’s susceptibility to enzymatic breakdown. Two dimensional 13C solid state NMR was initially employed to characterise the polymer composition, mobility, and spatial organisation of the intact isotopically labelled Sphagnum fuscum cell wall. Comparing S. fuscum with the model moss Physcomitrium patens and the eudicot Arabidopsis thaliana revealed that its wall is broadly built from the same major polymer classes found across land plants, including Iβ cellulose, hemicelluloses such as galactomannan and xyloglucan, and pectins. While moss specific modifications were apparent, such as the absence of canonical xylan conformations typical of vascular plants and the presence of an unidentified β-glucan like polymer, differences in the mobility of certain polysaccharides suggested differences in the incorporation or fine structure of wall polysaccharides in S. fuscum relative to the model moss. Targeted enzymatic hydrolysis was then used to probe the structure and accessibility of wall polymers identified by 2D ssNMR. Although previously described hemicelluloses were present, they remained resistant to enzymatic hydrolysis under standard alkali pretreatments that readily enable their breakdown in vascular plant controls. Screening multiple pretreatments revealed that Sphagnum walls are compositionally familiar but architecturally fortified, with a unique phenolic caging complex that blocks alkali and enzymatic access. Only when oxidation of phenolic compounds precedes alkali treatment can wall carbohydrates be easily digested. Once these barriers were removed, polysaccharides in 4000 year old peat samples became susceptible to enzymatic hydrolysis, revealing that such interactions may play a vital structural role in the long term storage of Sphagnum moss cell wall carbohydrates in peat
Degree
thesis:*- Name dc:type.qualificationname
- Doctor of Philosophy (PhD)
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2025
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Kelleher, Darragh
- Advisors dc:contributor.advisor
-
- Paul, Dupree
- Theodora, Tryfona
Subjects
dc:subject × 9Rights
dc:rightsIdentifiers
dc:identifier.*- DOI dc:identifier.doi
- https://doi.org/10.17863/CAM.124207
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/394136