title: Microbial community stratification linked to utilization of carbohydrates and phosphorus limitation in a boreal peatland at Marcell Experimental Forest, Minnesota, USA.
abstract: This study investigated the abundance, distribution, and composition of microbial communities at the watershed scale in a boreal peatland within the Marcell Experimental Forest (MEF), Minnesota, USA. Through a close coupling of next-generation sequencing, biogeochemistry, and advanced analytical chemistry, a biogeochemical hot spot was revealed in the mesotelm (30- to 50-cm depth) as a pronounced shift in microbial community composition in parallel with elevated peat decomposition. The relative abundance of Acidobacteria and the Syntrophobacteraceae, including known hydrocarbon-utilizing genera, was positively correlated with carbohydrate and organic acid content, showing a maximum in the mesotelm. The abundance of Archaea (primarily crenarchaeal groups 1.1c and 1.3) increased with depth, reaching up to 60% of total small-subunit (SSU) rRNA gene sequences in the deep peat below the 75-cm depth. Stable isotope geochemistry and potential rates of methane production paralleled vertical changes in methanogen community composition to indicate a predominance of acetoclastic methanogenesis mediated by the Methanosarcinales in the mesotelm, while hydrogen-utilizing methanogens predominated in the deeper catotelm. RNA-derived pyrosequence libraries corroborated DNA sequence data to indicate that the above-mentioned microbial groups are metabolically active in the mid-depth zone. Fungi showed a maximum in rRNA gene abundance above the 30-cm depth, which comprised only an average of 0.1% of total bacterial and archaeal rRNA gene abundance, indicating prokaryotic dominance. Ratios of C to P enzyme activities approached 0.5 at the acrotelm and catotelm, indicating phosphorus limitation. In contrast, P limitation pressure appeared to be relieved in the mesotelm, likely due to P solubilization by microbial production of organic acids and C-P lyases. Based on path analysis and the modeling of community spatial turnover, we hypothesize that P limitation outweighs N limitation at MEF, and microbial communities are structured by the dominant shrub, Chamaedaphne calyculata, which may act as a carbon source for major consumers in the peatland.
authors.affiliation: Georgia Institute of Technology, Schools of Biology and Earth & Atmospheric Sciences, Atlanta, Georgia, USA.
authors.forename: Xueju
authors.initials: X
authors.lastname: Lin
authors.forename: Malak M
authors.initials: MM
authors.lastname: Tfaily
authors.forename: J Megan
authors.initials: JM
authors.lastname: Steinweg
authors.forename: Patrick
authors.initials: P
authors.lastname: Chanton
authors.forename: Kaitlin
authors.initials: K
authors.lastname: Esson
authors.forename: Zamin K
authors.initials: ZK
authors.lastname: Yang
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Chanton
authors.forename: William
authors.initials: W
authors.lastname: Cooper
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Schadt
authors.forename: Joel E
authors.initials: JE
authors.lastname: Kostka
mesh_terms: D001105:Archaea / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D058448:Biota; D050260:Carbohydrate Metabolism; D002623:Chemistry Techniques, Analytical; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D065928:Forests; D005658:Fungi / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D008910:Minnesota; D010758:Phosphorus / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology
chemical_list: D004275:DNA, Ribosomal; D012987:Soil; D010758:Phosphorus