Microbial Communities and Interactions of Nitrogen Oxides With Methanogenesis in Diverse Peatlands of the Amazon Basin

Abstract

Tropical peatlands are hotspots of methane (CH4) production but present high variation and emission uncertainties in the Amazon region. This is because the controlling factors of methane production in tropical peats are not yet well documented. Although inhibitory effects of nitrogen oxides (NOx) on methanogenic activity are known from pure culture studies, the role of NOx in the methane cycling of peatlands remains unexplored. Here, we investigated the CH4 content, soil geochemistry and microbial communities along 1-m-soil profiles and assessed the effects of soil NOx and nitrous oxide (N2O) on methanogenic abundance and activity in three peatlands of the Pastaza-Marañón foreland basin. The peatlands were distinct in pH, DOC, nitrate pore water concentrations, C/N ratios of shallow soils, redox potential, and 13C enrichment in dissolved inorganic carbon and CH4 pools, which are primarily contingent on H2-dependent methanogenesis. Molecular 16S rRNA and mcrA gene data revealed diverse and novel methanogens varying across sites. Importantly, we also observed a strong stratification in relative abundances of microbial groups involved in NOx cycling, along with a concordant stratification of methanogens. The higher relative abundance of ammonia-oxidizing archaea (Thaumarchaeota) in acidic oligotrophic peat than ammonia-oxidizing bacteria (Nitrospira) is noteworthy as putative sources of NOx. Experiments testing the interaction of NOx species and methanogenesis found that the latter showed differential sensitivity to nitrite (up to 85% reduction) and N2O (complete inhibition), which would act as an unaccounted CH4 control in these ecosystems. Overall, we present evidence of diverse peatlands likely differently affected by inhibitory effects of nitrogen species on methanogens as another contributor to variable CH4 fluxes.

Analysis of the Bacterial Biocenosis of Activated Sludge Treated with Leachate from Municipal Landfills

“…Candidimonas nitroreducens was first isolated from wastewater sludge compost [77], belongs to the family Alcaligenaceae, and has a nitrate-reducing role [78]. On the other hand, N. hamburgensis oxidizes nitrite to nitrate, moreover, it exhibits resistance to heavy metals and is thought to carry out catabolism pathways of aromatic, organic and monocarbon compounds [79].…”

BinaRena: a dedicated interactive platform for human-guided exploration and binning of metagenomes

“…Genome-resolved metagenomics is widely used to understand potential biological mechanisms within an ecosystem and its distribution across the community. Nitrogen cycling within tropical peatlands is relatively understudied, yet there is evidence that it is closely interconnected with release of greenhouse gasses from these environments 48,49 . Here we used BinaRena to explore the distribution of nitrogen cycling genes involved in pathways such as dissimilatory nitrate reduction, denitrification, nitrification, and nitrogen fixation.…”

Genes and genome-resolved metagenomics reveal the microbial functional make up of Amazon peatlands under geochemical gradients

“…We studied the soil microbial communities from three peatlands within the PMFB: Buena Vista (BVA), Quistococha (QUI), and San Jorge (SJO). These study sites capture a broad range of heterogeneity of these peatlands, which include gradients in geochemistry, pH, hydrology, vegetation, GHG flux and microbial composition as detailed elsewhere [10,13,19,26] and summarized in Supplementary coinciding with expeditions at the peak of dry season and early wet season before regional flooding as periods where the microbial activity and composition is likely most distincy and thus sought to be captured. Triplicate 0.5 grams of soil were placed in sterile tubes with MoBio Lifeguard stabilization solution (MoBio, United States).…”

“…The copyright holder for this preprint this version posted December 19, 2022. ; https://doi.org/10.1101/2022.12.19.521090 doi: bioRxiv preprint metagenomes sequenced from Buena Vista (BVA), Quistococha (QUI), and San Jorge (SJO) peatlands that represent a nutrient gradient, from high to low, respectively, in the PMFB [13,19].…”

“…The copyright holder for this preprint this version posted December 19, 2022. ; https://doi.org/10.1101/2022.12. 19.521090 doi: bioRxiv preprint 4 ombrotrophic sites with far lower concentrations of minerals and a more acidic pH. Despite a scarcity of available data, preliminary observations indicate that tropical minerotrophic sites are predominately inhabited by Alphaproteobacteria, Gammaproteobacteria, and hydrogen metabolizing Archaea [13,17].…”