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  • 1
    Language: English
    In: Applied and environmental microbiology, August 2012, Vol.78(16), pp.5584-96
    Description: Palsa peats are characterized by elevated, circular frost heaves (peat soil on top of a permanently frozen ice lens) and are strong to moderate sources or even temporary sinks for the greenhouse gas nitrous oxide (N(2)O). Palsa peats are predicted to react sensitively to global warming. The acidic palsa peat Skalluvaara (approximate pH 4.4) is located in the discontinuous permafrost zone in northwestern Finnish Lapland. In situ N(2)O fluxes were spatially variable, ranging from 0.01 to -0.02 μmol of N(2)O m(-2) h(-1). Fertilization with nitrate stimulated in situ N(2)O emissions and N(2)O production in anoxic microcosms without apparent delay. N(2)O was subsequently consumed in microcosms. Maximal reaction velocities (v(max)) of nitrate-dependent denitrification approximated 3 and 1 nmol of N(2)O per h per gram (dry weight [g(DW)]) in soil from 0 to 20 cm and below 20 cm of depth, respectively. v(max) values of nitrite-dependent denitrification were 2- to 5-fold higher than the v(max) nitrate-dependent denitrification, and v(max) of N(2)O consumption was 1- to 6-fold higher than that of nitrite-dependent denitrification, highlighting a high N(2)O consumption potential. Up to 12 species-level operational taxonomic units (OTUs) of narG, nirK and nirS, and nosZ were retrieved. Detected OTUs suggested the presence of diverse uncultured soil denitrifiers and dissimilatory nitrate reducers, hitherto undetected species, as well as Actino-, Alpha-, and Betaproteobacteria. Copy numbers of nirS always outnumbered those of nirK by 2 orders of magnitude. Copy numbers of nirS tended to be higher, while copy numbers of narG and nosZ tended to be lower in 0- to 20-cm soil than in soil below 20 cm. The collective data suggest that (i) the source and sink functions of palsa peat soils for N(2)O are associated with denitrification, (ii) actinobacterial nitrate reducers and nirS-type and nosZ-harboring proteobacterial denitrifiers are important players, and (iii) acidic soils like palsa peats represent reservoirs of diverse acid-tolerant denitrifiers associated with N(2)O fluxes.
    Keywords: Denitrification ; Soil Microbiology ; Actinobacteria -- Classification ; Nitrates -- Metabolism
    ISSN: 00992240
    E-ISSN: 1098-5336
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  • 2
    Language: English
    In: PLoS ONE, April 10, 2015, Vol.10(4)
    Description: Peatlands cover more than 30% of the Finnish land area and impact N.sub.2 O fluxes. Denitrifiers release N.sub.2 O as an intermediate or end product. In situ N.sub.2 O emissions of a near pH neutral pristine fen soil in Finnish Lapland were marginal during gas chamber measurements. However, nitrate and ammonium fertilization significantly stimulated in situ N.sub.2 O emissions. Stimulation with nitrate was stronger than with ammonium. N.sub.2 O was produced and subsequently consumed in gas chambers. In unsupplemented anoxic microcosms, fen soil produced N.sub.2 O only when acetylene was added to block nitrous oxide reductase, suggesting complete denitrification. Nitrate and nitrite stimulated denitrification in fen soil, and maximal reaction velocities (v.sub.max) of nitrate or nitrite dependent denitrification where 18 and 52 nmol N.sub.2 O h.sup.-1 g.sub.DW .sup.-1, respectively. N.sub.2 O was below 30% of total produced N gases in fen soil when concentrations of nitrate and nitrite were 500 [mu]M. v.sub.max for N.sub.2 O consumption was up to 36 nmol N.sub.2 O h.sup.-1 g.sub.DW .sup.-1 . Denitrifier diversity was assessed by analyses of narG, nirK/nirS, and nosZ (encoding nitrate-, nitrite-, and nitrous oxide reductases, respectively) by barcoded amplicon pyrosequencing. Analyses of ~14,000 quality filtered sequences indicated up to 25 species-level operational taxonomic units (OTUs), and up to 359 OTUs at 97% sequence similarity, suggesting diverse denitrifiers. Phylogenetic analyses revealed clusters distantly related to publicly available sequences, suggesting hitherto unknown denitrifiers. Representatives of species-level OTUs were affiliated with sequences of unknown soil bacteria and Actinobacterial, Alpha-, Beta-, Gamma-, and Delta-Proteobacterial sequences. Comparison of the 4 gene markers at 97% similarity indicated a higher diversity of narG than for the other gene markers based on Shannon indices and observed number of OTUs. The collective data indicate (i) a high denitrification and N.sub.2 O consumption potential, and (ii) a highly diverse, nitrate limited denitrifier community associated with potential N.sub.2 O fluxes in a pH-neutral fen soil.
    Keywords: Nitrous Oxide -- Environmental Aspects ; Nitrous Oxide -- Research ; Denitrification -- Physiological Aspects ; Denitrification -- Environmental Aspects ; Denitrification -- Research
    ISSN: 1932-6203
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Applied and Environmental Microbiology, 2012, Vol.78(16), p.5584(13)
    Description: An analysis is performed to investigate the Actinobacterial nitrate reducers and Proteobacterial denitrifiers, which are abundant in [N.sub.2]O-metabolizing palsa peat. The collective data helps in understanding the source and sink functions of palsa peat soils for [N.sub.2]O.
    Keywords: Microbial Metabolism – Research ; Nitrates – Chemical Properties ; Nitrogen Fixation – Research ; Peat – Composition ; Proteobacteria – Physiological Aspects ; Soil Microbiology – Research
    ISSN: 0099-2240
    ISSN: 10985336
    E-ISSN: 10985336
    Source: Cengage Learning, Inc.
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  • 4
    Language: English
    In: Sensors & Actuators: B. Chemical, 2011, Vol.158(1), pp.313-318
    Description: An electrochemical biosensor was optimised for the analysis of volatile alcohols directly from the gas phase without prior absorption or pre-concentration. The sensor is based on the alcohol oxidase ( ) catalyzed conversion of ethanol and the amperometric detection of the generated hydrogen peroxide. Key part of the three-electrode set-up was a gas-diffusion working electrode (potential: +600 mV vs. Ag/AgCl) that consisted of a porous Teflon membrane coated with a thin platinum layer. Headspace samples were analysed for alcohols and used to derive alcohol concentrations in the liquid phase. The biosensor had a sensitivity of 3.43 μA/mM for ethanol, a response time of 69 s, a linear dynamic range of 0.10–30 mM, a theoretical detection limit (3 〈 S/N) of 9.9 μM, and a stability of 86% during continuous operation (18 h @ 1 mM ethanol). Using one sensor on three consecutive days, the mean coefficient of variation was 1.3% (three measurements each day @ 10 mM ethanol). Alcohol contents of three apple juices determined with the biosensor were in the range 0.30 g/l–0.67 g/l (equivalent to 6.51 mM–14.5 mM). However, ethanol contents determined by high pressure liquid chromatography coupled to refractive index detection (HPLC-RI) and by a commercial enzyme test kit based on alcohol dehydrogenase ranged from 0.12 g/l to 0.38 g/l (equivalent to 2.60 mM–8.25 mM). Both indicate that the biosensor detected alcohols other than ethanol in the apple juices. HPLC-RI coupled to the biosensor in a flow-through configuration demonstrated that the biosensor detected methanol concomitant to ethanol. Thus, the biosensor could perform a qualitative analysis of the total content of volatile alcohols in apple juices by analysing the gas phase above the sample. This offers the additional advantage that possible, non-volatile interfering substances in the liquid sample cannot impair the measurement.
    Keywords: Apple Juice ; Ethanol ; Methanol ; Alcohol Oxidase ; Amperometric Biosensor ; Gas-Phase Sensor ; Engineering
    ISSN: 0925-4005
    E-ISSN: 1873-3077
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  • 5
    Language: English
    In: PLoS ONE, 01 January 2015, Vol.10(4), p.e0123123
    Description: Peatlands cover more than 30% of the Finnish land area and impact N2O fluxes. Denitrifiers release N2O as an intermediate or end product. In situ N2O emissions of a near pH neutral pristine fen soil in Finnish Lapland were marginal during gas chamber measurements. However, nitrate and ammonium fertilization significantly stimulated in situ N2O emissions. Stimulation with nitrate was stronger than with ammonium. N2O was produced and subsequently consumed in gas chambers. In unsupplemented anoxic microcosms, fen soil produced N2O only when acetylene was added to block nitrous oxide reductase, suggesting complete denitrification. Nitrate and nitrite stimulated denitrification in fen soil, and maximal reaction velocities (vmax) of nitrate or nitrite dependent denitrification where 18 and 52 nmol N2O h-1 gDW-1, respectively. N2O was below 30% of total produced N gases in fen soil when concentrations of nitrate and nitrite were 〈500 μM. vmax for N2O consumption was up to 36 nmol N2O h-1 gDW-1. Denitrifier diversity was assessed by analyses of narG, nirK/nirS, and nosZ (encoding nitrate-, nitrite-, and nitrous oxide reductases, respectively) by barcoded amplicon pyrosequencing. Analyses of ~14,000 quality filtered sequences indicated up to 25 species-level operational taxonomic units (OTUs), and up to 359 OTUs at 97% sequence similarity, suggesting diverse denitrifiers. Phylogenetic analyses revealed clusters distantly related to publicly available sequences, suggesting hitherto unknown denitrifiers. Representatives of species-level OTUs were affiliated with sequences of unknown soil bacteria and Actinobacterial, Alpha-, Beta-, Gamma-, and Delta-Proteobacterial sequences. Comparison of the 4 gene markers at 97% similarity indicated a higher diversity of narG than for the other gene markers based on Shannon indices and observed number of OTUs. The collective data indicate (i) a high denitrification and N2O consumption potential, and (ii) a highly diverse, nitrate limited denitrifier community associated with potential N2O fluxes in a pH-neutral fen soil.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 6
    In: Global Change Biology, June 2015, Vol.21(6), pp.2357-2365
    Description: Nitrogen (N) nutrition in pristine peatlands relies on the natural input of inorganic N through atmospheric deposition or biological dinitrogen (N) fixation. However, N fixation and its significance for N cycling, plant productivity, and peat buildup are mostly associated with the presence of mosses. Here, we report high nonsymbiotic N‐fixation rates in two pristine Patagonian bogs with diversified vegetation and natural N deposition. Nonsymbiotic N fixation was measured in samples from 0 to 10, 10 to 20, and 40 to 50 cm depth using the N assay as well as the acetylene reduction assay (). The considerably underestimated N fixation and can thus not be recommended for peatland studies. Based on the N assay, high nonsymbiotic N‐fixation rates of 0.3–1.4 μmol N g day were found down to 50 cm under micro‐oxic conditions (2 vol.%) in samples from plots covered by or by vascular cushion plants, latter characterized by dense and deep aerenchyma roots. Peat N concentrations point to greater potential of nonsymbiotic N fixation under cushion plants, likely because of the availability of easily decomposable organic compounds and oxic conditions in the rhizosphere. In the plots, high N fixation below 10 cm depth rather reflects the potential during dry periods or low water level when oxygen penetrates the top peat layer and triggers peat mineralization. Natural abundance of the N isotope of live (5.6 ‰) from 0 to 10 cm points to solely N uptake from atmospheric deposition and nonsymbiotic N fixation. A mean N signature of −0.7 ‰ of peat from the cushion plant plots indicates additional N supply from N mineralization. Our findings suggest that nonsymbiotic N fixation overcomes N deficiency in different vegetation communities and has great significance for N cycling and peat accumulation in pristine peatlands.
    Keywords: 15 N ; Acetylen Reduction Assay ; Cushion Plant ; Diazotroph ; Nitrogen Cycle ; Nitrogen Fixation ; Peatland ; Spaghnum
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 7
    In: Applied and Environmental Microbiology, 2010, Vol. 76(6), p.2027
    Description: Newly designed primers for [Fe-Fe]-hydrogenases indicated that (i) fermenters, acetogens, and undefined species in a fen harbor hitherto unknown hydrogenases and (ii) Clostridium- and Thermosinus-related primary fermenters, as well as secondary fermenters related to sulfate or iron reducers might be responsible for hydrogen production in the fen. Comparative analysis of [Fe-Fe]-hydrogenase and 16S rRNA gene-based phylogenies indicated the presence of homologous multiple hydrogenases per organism and inconsistencies between 16S rRNA gene- and [Fe-Fe]-hydrogenase-based phylogenies, necessitating appropriate qualification of [Fe-Fe]-hydrogenase gene data for diversity analyses. [PUBLICATION ]
    Keywords: Ribonucleic Acid–RNA ; Genes ; Bacteria ; Comparative Analysis ; Microbiology;
    ISSN: 0099-2240
    ISSN: 00992240
    E-ISSN: 10985336
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  • 8
    In: Applied and Environmental Microbiology, 2010, Vol. 76(4), p.1125
    Description: The denitrifier community of an nitrous oxide ([N.sub.2]O)-emitting fen (pH 4.7 to 5.2) is examined. The studies have shown that the regional fen has harbored novel, highly diverse, acid-tolerant denitrifier communities that are capable of complete denitrification and consumption of atmospheric [N.sub.2]O at in situ pH.
    Keywords: Denitrification – Analysis ; Fermentation – Analysis ; Nitrobacteraceae – Genetic Aspects ; Nitrobacteraceae – Environmental Aspects ; Nitrous Oxide – Environmental Aspects ; Restriction Fragment Length Polymorphism Analysis – Usage;
    ISSN: 0099-2240
    ISSN: 00992240
    E-ISSN: 10985336
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  • 9
    Language: English
    In: Applied and environmental microbiology, February 2010, Vol.76(4), pp.1125-34
    Description: Wetlands are sources of denitrification-derived nitrous oxide (N2O). Thus, the denitrifier community of an N2O-emitting fen (pH 4.7 to 5.2) was investigated. N2O was produced and consumed to subatmospheric concentrations in unsupplemented anoxic soil microcosms. Total cell counts and most probable numbers of denitrifiers approximated 10(11) cells x g(DW)(-1) (where DW is dry weight) and 10(8) cells x g(DW)(-1), respectively, in both 0- to 10-cm and 30- to 40-cm depths. Despite this uniformity, depth-related maximum reaction rate (v(max)) values for denitrification in anoxic microcosms ranged from 1 to 24 and -19 to -105 nmol N2O h(-1) x g(DW)(-1), with maximal values occurring in the upper soil layers. Denitrification was enhanced by substrates that might be formed via fermentation in anoxic microzones of soil. N2O approximated 40% of total nitrogenous gases produced at in situ pH, which was likewise the optimal pH for denitrification. Gene libraries of narG and nosZ (encoding nitrate reductase and nitrous oxide reductase, respectively) from fen soil DNA yielded 15 and 18 species-level operational taxonomic units, respectively, many of which displayed phylogenetic novelty and were not closely related to cultured organisms. Although statistical analyses of narG and nosZ sequences indicated that the upper 20 cm of soil contained the highest denitrifier diversity and species richness, terminal restriction fragment length polymorphism analyses of narG and nosZ revealed only minor differences in denitrifier community composition from a soil depth of 0 to 40 cm. The collective data indicate that the regional fen harbors novel, highly diverse, acid-tolerant denitrifier communities capable of complete denitrification and consumption of atmospheric N2O at in situ pH.
    Keywords: Soil Microbiology ; Wetlands ; Nitrous Oxide -- Metabolism ; Soil -- Analysis
    ISSN: 00992240
    E-ISSN: 1098-5336
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  • 10
    Language: English
    In: PLoS ONE, April 10, 2015, Vol.10(4)
    Description: Peatlands cover more than 30% of the Finnish land area and impact N.sub.2 O fluxes. Denitrifiers release N.sub.2 O as an intermediate or end product. In situ N.sub.2 O emissions of a near pH neutral pristine fen soil in Finnish Lapland were marginal during gas chamber measurements. However, nitrate and ammonium fertilization significantly stimulated in situ N.sub.2 O emissions. Stimulation with nitrate was stronger than with ammonium. N.sub.2 O was produced and subsequently consumed in gas chambers. In unsupplemented anoxic microcosms, fen soil produced N.sub.2 O only when acetylene was added to block nitrous oxide reductase, suggesting complete denitrification. Nitrate and nitrite stimulated denitrification in fen soil, and maximal reaction velocities (v.sub.max) of nitrate or nitrite dependent denitrification where 18 and 52 nmol N.sub.2 O h.sup.-1 g.sub.DW .sup.-1, respectively. N.sub.2 O was below 30% of total produced N gases in fen soil when concentrations of nitrate and nitrite were 500 [mu]M. v.sub.max for N.sub.2 O consumption was up to 36 nmol N.sub.2 O h.sup.-1 g.sub.DW .sup.-1 . Denitrifier diversity was assessed by analyses of narG, nirK/nirS, and nosZ (encoding nitrate-, nitrite-, and nitrous oxide reductases, respectively) by barcoded amplicon pyrosequencing. Analyses of ~14,000 quality filtered sequences indicated up to 25 species-level operational taxonomic units (OTUs), and up to 359 OTUs at 97% sequence similarity, suggesting diverse denitrifiers. Phylogenetic analyses revealed clusters distantly related to publicly available sequences, suggesting hitherto unknown denitrifiers. Representatives of species-level OTUs were affiliated with sequences of unknown soil bacteria and Actinobacterial, Alpha-, Beta-, Gamma-, and Delta-Proteobacterial sequences. Comparison of the 4 gene markers at 97% similarity indicated a higher diversity of narG than for the other gene markers based on Shannon indices and observed number of OTUs. The collective data indicate (i) a high denitrification and N.sub.2 O consumption potential, and (ii) a highly diverse, nitrate limited denitrifier community associated with potential N.sub.2 O fluxes in a pH-neutral fen soil.
    Keywords: Nitrous Oxide – Environmental Aspects ; Nitrous Oxide – Research ; Denitrification – Physiological Aspects ; Denitrification – Environmental Aspects ; Denitrification – Research
    ISSN: 1932-6203
    Source: Cengage Learning, Inc.
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