title: Microbial metabolic potential for carbon degradation and nutrient (nitrogen and phosphorus) acquisition in an ombrotrophic peatland.
abstract: This study integrated metagenomic and nuclear magnetic resonance (NMR) spectroscopic approaches to investigate microbial metabolic potential for organic matter decomposition and nitrogen (N) and phosphorus (P) acquisition in soils of an ombrotrophic peatland in the Marcell Experimental Forest (MEF), Minnesota, USA. This analysis revealed vertical stratification in key enzymatic pathways and taxa containing these pathways. Metagenomic analyses revealed that genes encoding laccases and dioxygenases, involved in aromatic compound degradation, declined in relative abundance with depth, while the relative abundance of genes encoding metabolism of amino sugars and all four saccharide groups increased with depth in parallel with a 50% reduction in carbohydrate content. Most Cu-oxidases were closely related to genes from Proteobacteria and Acidobacteria, and type 4 laccase-like Cu-oxidase genes were >8 times more abundant than type 3 genes, suggesting an important and overlooked role for type 4 Cu-oxidase in phenolic compound degradation. Genes associated with sulfate reduction and methanogenesis were the most abundant anaerobic respiration genes in these systems, with low levels of detection observed for genes of denitrification and Fe(III) reduction. Fermentation genes increased in relative abundance with depth and were largely affiliated with Syntrophobacter. Methylocystaceae-like small-subunit (SSU) rRNA genes, pmoA, and mmoX genes were more abundant among methanotrophs. Genes encoding N2 fixation, P uptake, and P regulons were significantly enriched in the surface peat and in comparison to other ecosystems, indicating N and P limitation. Persistence of inorganic orthophosphate throughout the peat profile in this P-limiting environment indicates that P may be bound to recalcitrant organic compounds, thus limiting P bioavailability in the subsurface. Comparative metagenomic analysis revealed a high metabolic potential for P transport and starvation, N2 fixation, and oligosaccharide degradation at MEF relative to other wetland and soil environments, consistent with the nutrient-poor and carbohydrate-rich conditions found in this Sphagnum-dominated boreal 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: Stefan J
authors.initials: SJ
authors.lastname: Green
authors.forename: J Megan
authors.initials: JM
authors.lastname: Steinweg
authors.forename: Patrick
authors.initials: P
authors.lastname: Chanton
authors.forename: Aopeau
authors.initials: A
authors.lastname: Imvittaya
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Chanton
authors.forename: William
authors.initials: W
authors.lastname: Cooper
authors.forename: Christopher
authors.initials: C
authors.lastname: Schadt
authors.forename: Joel E
authors.initials: JE
authors.lastname: Kostka
mesh_terms: D001419:Bacteria / Q000145:classification / Q000378:metabolism*; D058448:Biota; D002244:Carbon / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D056186:Metagenomics; D008910:Minnesota; D009584:Nitrogen / Q000378:metabolism*; D009930:Organic Chemicals / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*; D012988:Soil Microbiology
chemical_list: D009930:Organic Chemicals; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen