Impact of Warming on Greenhouse Gas Production and Microbial Diversity in Anoxic Peat From a Sphagnum-Dominated Bog (Grand Rapids, Minnesota, United States).
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SUBMITTER: Kolton M
PROVIDER: S-EPMC6498409 | biostudies-literature | 2019
REPOSITORIES: biostudies-literature
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Project description:The Bacteria community composition in an acidic Sphagnum peat bog (pH 3.9 to 4.5) was characterized by a combination of 16S rRNA gene clone library analysis, rRNA-targeted fluorescence in situ hybridization (FISH), and cultivation. Among 84 environmental 16S rRNA gene clones, a set of only 16 cloned sequences was closely related (>or=95% similarity) to taxonomically described organisms. Main groups of clones were affiliated with the Acidobacteria (24 clones), Alphaproteobacteria (20), Verrucomicrobia (13), Actinobacteria (8), Deltaproteobacteria (4), Chloroflexi (3), and Planctomycetes (3). The proportion of cells that hybridized with oligonucleotide probes specific for members of the domains Bacteria (EUB338-mix) and Archaea (ARCH915 and ARC344) accounted for only 12 to 22% of the total cell counts. Up to 24% of the EUB338-positive cells could be assigned by FISH to specific bacterial phyla. Alphaproteobacteria and Planctomycetes were the most numerous bacterial groups (up to 1.3x10(7) and 1.1x10(7) cells g-1 peat, respectively). In contrast to conventional plating techniques, a novel biofilm-mediated enrichment approach allowed us to isolate some representatives of predominant Bacteria groups, such as Acidobacteria and Planctomycetes. This novel strategy has great potential to enable the isolation of a significant proportion of the peat bog bacterial diversity.
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Project description:BackgroundThe Grand Rapids Arch Collapse Classification system was devised in 2011 to assist physicians' and patients' understanding of the mechanisms underlying arch collapse. Five types of arch collapse are described, based on which part of the foot or ankle is affected. The purpose of this study was to determine the inter- and intrarater reliability of this classification system when used by physicians with various levels of training.MethodsA senior author identified a stratified selection of 50 patients (10 per classification type) who presented with foot/ankle pain and suitable radiographs. A survey was designed using prediagnosis radiographs and clinical synopses of the patient's chart. The survey consisted of a description of the classification scheme and the 50 cases in a randomized order. Eight weeks later, they repeated the test to analyze for intra-rater agreement.ResultsOf the 33 physicians who received the survey, 26 completed the first round (16 attendings, 4 foot and ankle fellows, and 6 residents). Overall, there was substantial agreement among raters in all five types. Kappa scores for each type were 0.72, 0.65, 0.72, 0.70, 0.63, respectively. The combined kappa score was 0.68. After 8 weeks, 13 of the 26 participants repeated the study. A Kappa analysis was once again performed for the 13 respondents, which produced a substantial level of agreement with a value of 0.74 for intrarater reliability.ConclusionThe Grand Rapids Arch Collapse Classification system was designed to provide an accessible mechanism for physicians to consistently describe arch collapse, its effects, and the conditions associated with it. The utility of this system is wholly reliant on the repeatability among clinicians. This study has demonstrated that the classification system has substantial rates of reliability among physicians of different levels of experience and training.Level of evidenceLevel IV.
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Project description:Highly enriched methanotrophic communities (> 25 serial transfers) were obtained from acidic ombrotrophic peat bogs from four boreal forest sites. The enrichment strategy involved using media conditions that were associated with the highest rates of methane uptake by the original peat samples, namely, the use of diluted mineral medium of low buffering capacity, moderate incubation temperature (20 degrees C), and pH values of 3 to 6. Enriched communities contained a mixture of rod-shaped bacteria arranged in aggregates with a minor contribution of Hyphomicrobium-like cells. The growth stoichiometry of isolates was characteristic of methanotrophic bacteria (CH4/O2/CO2 = 1:1.1:0.59), with an average apparent yield of 0.41 +/- 0.03 g of biomass C/g of CH4-C. DNA from each enrichment yielded a PCR product of the expected size with primers for both mmoX and mmoY genes of soluble methane monooxygenase. Two types of sequences were obtained for PCR-amplified fragments of mmoX. One of them exhibited high identity to the mmoX protein of the Methylocystis-Methylosinus group, whereas the other showed an equal level of divergence from both the Methylosinus-Methylocystis group and Methylococcus capsulatus (Bath) and formed a distinct branch. The pH optimum for growth and for CH4 uptake was 4.5 to 5.5, which is very similar to that for the optimum CH4 uptake observed in the original peat samples. These methanotrophs are moderate acidophiles rather than acidotolerant organisms, since their growth rate and methane uptake were much lower at neutral pH. The growth of the methanotrophic community was enhanced by using media with a very low salt content (20 to 200 mg/liter), more typical of their natural environment. All four enriched communities grew on N-free medium.
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Project description:Peatlands are one of the most important ecosystems due to their biodiversity and abundant organic compounds; therefore, it is important to observe how different plant species in peatlands react to changing environmental conditions. Sphagnum spp. are the main component of peatlands and are considered as the creator of conditions favorable for carbon storage in the form of peat. Sphagnum angustifolium and Sphagnum fallax are taxonomically very close species. To examine their adaptability to climate change, we studied the morphology and pigment content of these two species from environmental manipulation sites in Poland, where the environment was continuously manipulated for temperature and precipitation. The warming of peat was induced by using infrared heaters, whereas total precipitation was reduced by a curtain that cuts the nighttime precipitation. Morphology of S. angustifolium stayed under climate manipulation relatively stable. However, the main morphological parameters of S. fallax were significantly affected by precipitation reduction. Thus, this study indicates S. angustifolium is better adapted in comparison to S. fallax for drier and warmer conditions.
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Project description:Sphagnum-dominated peatlands comprise a globally important pool of soil carbon (C) and are vulnerable to climate change. While peat mosses of the genus Sphagnum are known to harbor diverse microbial communities that mediate C and nitrogen (N) cycling in peatlands, the effects of climate change on Sphagnum microbiome composition and functioning are largely unknown. We investigated the impacts of experimental whole-ecosystem warming on the Sphagnum moss microbiome, focusing on N2 fixing microorganisms (diazotrophs). To characterize the microbiome response to warming, we performed next-generation sequencing of small subunit (SSU) rRNA and nitrogenase (nifH) gene amplicons and quantified rates of N2 fixation activity in Sphagnum fallax individuals sampled from experimental enclosures over 2 years in a northern Minnesota, USA bog. The taxonomic diversity of overall microbial communities and diazotroph communities, as well as N2 fixation rates, decreased with warming (p < 0.05). Following warming, diazotrophs shifted from a mixed community of Nostocales (Cyanobacteria) and Rhizobiales (Alphaproteobacteria) to predominance of Nostocales. Microbiome community composition differed between years, with some diazotroph populations persisting while others declined in relative abundance in warmed plots in the second year. Our results demonstrate that warming substantially alters the community composition, diversity, and N2 fixation activity of peat moss microbiomes, which may ultimately impact host fitness, ecosystem productivity, and C storage potential in peatlands.
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Project description:A fast-growing, non-chromogenic, acid-fast-staining bacterium (DL90T) was isolated from a peat bog in northern Minnesota. On the basis of 16S rRNA gene sequence similarity (99.8 % identity with Mycolicibacterium septicum and 98 % with Mycolicibacterium peregrinum) and chemotaxonomic data (fatty acid content), strain DL90T represents a member of the genus Mycolicibacterium. Physiological tests (growth curves, biofilm formation, antibiotic sensitivity, colony morphologies and heat tolerance) and biochemical analysis (arylsulfatase activity and fatty acid profiles) distinguish DL90T from its closest relative M. septicum. Phylogenomic reconstruction of the 'Fortuitium-Vaccae' clade, digital DNA-DNA hybridization (DDH) values of 61 %, and average nucleotide identity (ANI) values of approximately 95 % indicate that DL90T is likely to be diverged from M. septicum. Thus, we propose that DL90T represents a novel species, given the name Mycolicibacterium nivoides with the type strain being isolate DL90T (=JCM 32796T=NCCB 100660T).
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Project description:Northern wetlands make up a substantial terrestrial carbon sink and are often dominated by decay-resistant Sphagnum mosses. Recent studies have shown that planctomycetes appear to be involved in degradation of Sphagnum-derived debris. Novel trimethylornithine (TMO) lipids have recently been characterized as abundant lipids in various Sphagnum wetland planctomycete isolates, but their occurrence in the environment has not yet been confirmed. We applied a combined intact polar lipid (IPL) and molecular analysis of peat cores collected from two northern wetlands (Saxnäs Mosse [Sweden] and Obukhovskoye [Russia]) in order to investigate the preferred niche and abundance of TMO-producing planctomycetes. TMOs were present throughout the profiles of Sphagnum bogs, but their concentration peaked at the oxic/anoxic interface, which coincided with a maximum abundance of planctomycete-specific 16S rRNA gene sequences. The sequences detected at the oxic/anoxic interface were affiliated with the Isosphaera group, while sequences present in the anoxic peat layers were related to an uncultured planctomycete group. Pyrosequencing-based analysis identified Planctomycetes as the major bacterial group at the oxic/anoxic interface at the Obukhovskoye peat (54% of total 16S rRNA gene sequence reads), followed by Acidobacteria (19% reads), while in the Saxnäs Mosse peat, Acidobacteria were dominant (46%), and Planctomycetes contributed to 6% of the total reads. The detection of abundant TMO lipids in planctomycetes isolated from peat bogs and the lack of TMO production by cultures of acidobacteria suggest that planctomycetes are the producers of TMOs in peat bogs. The higher accumulation of TMOs at the oxic/anoxic interface and the change in the planctomycete community with depth suggest that these IPLs could be synthesized as a response to changing redox conditions at the oxic/anoxic interface.
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Project description:Microbial N2 fixation (diazotrophy) represents an important nitrogen source to oligotrophic peatland ecosystems, which are important sinks for atmospheric CO2 and are susceptible to the changing climate. The objectives of this study were (i) to determine the active microbial group and type of nitrogenase mediating diazotrophy in an ombrotrophic Sphagnum-dominated peat bog (the S1 peat bog, Marcell Experimental Forest, Minnesota, USA); and (ii) to determine the effect of environmental parameters (light, O2, CO2, and CH4) on potential rates of diazotrophy measured by acetylene (C2H2) reduction and 15N2 incorporation. A molecular analysis of metabolically active microbial communities suggested that diazotrophy in surface peat was primarily mediated by Alphaproteobacteria (Bradyrhizobiaceae and Beijerinckiaceae). Despite higher concentrations of dissolved vanadium ([V] 11 nM) than molybdenum ([Mo] 3 nM) in surface peat, a combination of metagenomic, amplicon sequencing, and activity measurements indicated that Mo-containing nitrogenases dominate over the V-containing form. Acetylene reduction was only detected in surface peat exposed to light, with the highest rates observed in peat collected from hollows with the highest water contents. Incorporation of 15N2 was suppressed 90% by O2 and 55% by C2H2 and was unaffected by CH4 and CO2 amendments. These results suggest that peatland diazotrophy is mediated by a combination of C2H2-sensitive and C2H2-insensitive microbes that are more active at low concentrations of O2 and show similar activity at high and low concentrations of CH4 IMPORTANCE Previous studies indicate that diazotrophy provides an important nitrogen source and is linked to methanotrophy in Sphagnum-dominated peatlands. However, the environmental controls and enzymatic pathways of peatland diazotrophy, as well as the metabolically active microbial populations that catalyze this process, remain in question. Our findings indicate that oxygen levels and photosynthetic activity override low nutrient availability in limiting diazotrophy and that members of the Alphaproteobacteria (Rhizobiales) catalyze this process at the bog surface using the molybdenum-based form of the nitrogenase enzyme.
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Project description:Globally, peatlands have been affected by drainage and peat extraction, with adverse effects on their functioning and services. To restore peat-forming vegetation, drained bogs are being rewetted on a large scale. Although this practice results in higher groundwater levels, unfortunately it often creates deep lakes in parts where peat was extracted to greater depths than the surroundings. Revegetation of these deeper waters by peat mosses appears to be challenging due to strong abiotic feedbacks that keep these systems in an undesired bare state. In this study, we theoretically explore if a floating peat mat and an open human-made bog lake can be considered two alternative stable states using a simple model, and experimentally test in the field whether stable states are present, and whether a state shift can be accomplished using floating biodegradable structures that mimic buoyant peat. We transplanted two peat moss species into these structures (pioneer sp. Sphagnum cuspidatum and later-successional sp. S. palustre) with and without additional organic substrate. Our model suggests that these open human-made bog lakes and floating peat mats can indeed be regarded as alternative stable states. Natural recovery by spontaneous peat moss growth, i.e., a state shift from open water to floating mats, is only possible when the water table is sufficiently shallow to avoid light limitation (<0.29 m at our site). Our experiment revealed that alternative stable states are present and that the floating structures facilitated the growth of pioneer S. cuspidatum and vascular plants. Organic substrate addition particularly facilitated vascular plant growth, which correlated to higher moss height. The structures remained too wet for the late-successional species S. palustre. We conclude that open water and floating peat mats in human-made bog lakes can be considered two alternative stable states, and that temporary floating establishment structures can induce a state shift from the open water state to peat-forming vegetation state. These findings imply that for successful restoration, there is a clear water depth threshold to enable peat moss growth and there is no need for addition of large amounts of donor-peat substrate. Correct species selection for restoration is crucial for success.
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Project description:Excess CO2 accumulated in soils is typically transported to the atmosphere through molecular diffusion along a concentration gradient. Because of the slow and constant nature of this process, a steady state between peat CO2 production and emissions is often established. However, in peatland ecosystems, high peat porosity could foster additional non-diffusive transport processes, whose dynamics may become important to peat CO2 storage, transport and emission. Based on a continuous record of in situ peat pore CO2 concentration within the unsaturated zone of a raised bog in southern Canada, we show that changes in wind speed create large diel fluctuations in peat pore CO2 store. Peat CO2 builds up overnight and is regularly flushed out the following morning. Persistently high wind speed during the day maintains the peat CO2 with concentrations close to that of the ambient air. At night, wind speed decreases and CO2 production overtakes the transport rate leading to the accumulation of CO2 in the peat. Our results indicate that the effective diffusion coefficient fluctuates based on wind speed and generally exceeds the estimated molecular diffusion coefficient. The balance between peat CO2 accumulation and transport is most dynamic within the range of 0-2 m s-1 wind speeds, which occurs over 75% of the growing season and dominates night-time measurements. Wind therefore drives considerable temporal dynamics in peat CO2 transport and storage, particularly over sub-daily timescales, such that peat CO2 emissions can only be directly related to biological production over longer timescales. The online version contains supplementary material available at 10.1007/s10021-024-00904-1.
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