Coupled Manganese Redox Cycling and Organic Carbon Degradation on Mineral Surfaces

2020 ◽  
Vol 54 (14) ◽  
pp. 8801-8810 ◽  
Author(s):  
Dong Ma ◽  
Juan Wu ◽  
Peng Yang ◽  
Mengqiang Zhu
Keyword(s):  
Organic Carbon ◽  
Redox Cycling ◽  
Mineral Surfaces ◽  
Carbon Degradation

scholarly journals Global budgets of organic carbon degradation pathways in marine sediments

2021 ◽  
Author(s):  
Dominik Hülse ◽  
James Bradley ◽  
Sebastiaan van de Velde ◽  
Andy Dale ◽  
Sandra Arndt ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Marine Sediments ◽  
Degradation Pathways ◽  
Global Budgets ◽  
Carbon Degradation

scholarly journals Imaging of Cellular Oxidoreductase Activity Suggests Mixotrophic Metabolisms in Thiomargarita spp

mBio ◽  
2017 ◽  
Vol 8 (6) ◽  
Author(s):  
Jake V. Bailey ◽  
Beverly E. Flood ◽  
Elizabeth Ricci ◽  
Nathalie Delherbe
Keyword(s):  
Organic Carbon ◽  
Time Course ◽  
Genomic Data ◽  
Metabolic Potential ◽  
Oxidoreductase Activity ◽  
Metabolic Plasticity ◽  
Hypoxic Conditions ◽  
Genomic Studies ◽  
Genomic Results ◽  
Carbon Degradation

ABSTRACT The largest known bacteria, Thiomargarita spp., have yet to be isolated in pure culture, but their large size allows for individual cells to be monitored in time course experiments or to be individually sorted for omics-based investigations. Here we investigated the metabolism of individual cells of Thiomargarita spp. by using a novel application of a tetrazolium-based dye that measures oxidoreductase activity. When coupled with microscopy, staining of the cells with a tetrazolium-formazan dye allows metabolic responses in Thiomargarita spp. to be to be tracked in the absence of observable cell division. Additionally, the metabolic activity of Thiomargarita sp. cells can be differentiated from the metabolism of other microbes in specimens that contain adherent bacteria. The results of our redox dye-based assay suggest that Thiomargarita is the most metabolically versatile under anoxic conditions, where it appears to express cellular oxidoreductase activity in response to the electron donors succinate, acetate, citrate, formate, thiosulfate, H2, and H2S. Under hypoxic conditions, formazan staining results suggest the metabolism of succinate and likely acetate, citrate, and H2S. Cells incubated under oxic conditions showed the weakest formazan staining response, and then only to H2S, citrate, and perhaps succinate. These results provide experimental validation of recent genomic studies of Candidatus Thiomargarita nelsonii that suggest metabolic plasticity and mixotrophic metabolism. The cellular oxidoreductase response of bacteria attached to the exterior of Thiomargarita also supports the possibility of trophic interactions between these largest of known bacteria and attached epibionts. IMPORTANCE The metabolic potential of many microorganisms that cannot be grown in the laboratory is known only from genomic data. Genomes of Thiomargarita spp. suggest that these largest of known bacteria are mixotrophs, combining lithotrophic metabolism with organic carbon degradation. Our use of a redox-sensitive tetrazolium dye to query the metabolism of these bacteria provides an independent line of evidence that corroborates the apparent metabolic plasticity of Thiomargarita observed in recently produced genomes. Finding new cultivation-independent means of testing genomic results is critical to testing genome-derived hypotheses on the metabolic potentials of uncultivated microorganisms. IMPORTANCE The metabolic potential of many microorganisms that cannot be grown in the laboratory is known only from genomic data. Genomes of Thiomargarita spp. suggest that these largest of known bacteria are mixotrophs, combining lithotrophic metabolism with organic carbon degradation. Our use of a redox-sensitive tetrazolium dye to query the metabolism of these bacteria provides an independent line of evidence that corroborates the apparent metabolic plasticity of Thiomargarita observed in recently produced genomes. Finding new cultivation-independent means of testing genomic results is critical to testing genome-derived hypotheses on the metabolic potentials of uncultivated microorganisms.

Adsorption and stabilization of organic carbon by mineral surfaces in soils

2006 ◽  
Vol 25 (S1) ◽  
pp. 263-264 ◽  
Author(s):  
Seunghun Kang ◽  
Saikat Ghosh ◽  
Baoshan Xing
Keyword(s):  
Organic Carbon ◽  
Mineral Surfaces

Biofilm increases permeate quality by organic carbon degradation in low pressure ultrafiltration

2015 ◽  
Vol 85 ◽  
pp. 512-520 ◽  
Author(s):  
A. Chomiak ◽  
J. Traber ◽  
E. Morgenroth ◽  
N. Derlon
Keyword(s):  
Organic Carbon ◽  
Low Pressure ◽  
Carbon Degradation

scholarly journals Age distribution, extractability, and stability of mineral-bound organic carbon in central European soils

2021 ◽  
Vol 18 (3) ◽  
pp. 1241-1257
Author(s):  
Marion Schrumpf ◽  
Klaus Kaiser ◽  
Allegra Mayer ◽  
Günter Hempel ◽  
Susan Trumbore
Keyword(s):  
Organic Carbon ◽  
Soil Depth ◽  
Coniferous Forest ◽  
Age Distribution ◽  
Chemical Oxidation ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Mineral Surfaces ◽  
Site Specific ◽  
13C Nuclear Magnetic Resonance

Abstract. The largest share of total soil organic carbon (OC) is associated with minerals. However, the factors that determine the amount and turnover of slower- versus faster-cycling components of mineral-associated carbon (MOC) are still poorly understood. Bioavailability of MOC is thought to be regulated by desorption, which can be facilitated by displacement and mobilization by competing ions. However, MOC stability is usually determined by exposure to chemical oxidation, which addresses the chemical stability of the organic compounds rather than the bonding strength of the OC–mineral bond. We used a solution of NaOH, a strong agent for desorption due to high pH, and NaF, adding F−, a strongly sorbing anion that can replace anionic organic molecules on mineral surfaces, to measure the maximum potentially desorbable MOC. For comparison, we measured maximal potential oxidation of MOC using heated H2O2. We selected MOC samples (> 1.6 g cm3) obtained from density fractionation of samples from three soil depth increments (0–5, 10–20, and 30–40 cm) of five typical soils of central Europe, with a range of clay and pedogenic oxide contents, and under different ecosystem types (one coniferous forest, two deciduous forests, one grassland, and one cropland). Extracts and residues were analysed for OC and 14C contents, and further chemically characterized by cross-polarization magic angle spinning 13C-nuclear magnetic resonance (CPMAS-13C-NMR). We expected that NaF–NaOH extraction would remove less and younger MOC than H2O2 oxidation and that the NaF–NaOH extractability of MOC is reduced in subsoils and soils with high pedogenic oxide contents. The results showed that a surprisingly consistent proportion of 58 ± 11 % (standard deviation) of MOC was extracted with NaF–NaOH across soils, independent of depth, mineral assemblage, or land use conditions. NMR spectra revealed strong similarities in the extracted organic matter, with more than 80 % of OC in the O/N (oxygen and/or nitrogen) alkyl and alkyl C region. Total MOC amounts were correlated with the content of pedogenic oxides across sites, independent of variations in total clay, and the same was true for OC in extraction residues. Thus, the uniform extractability of MOC may be explained by dominant interactions between OC and pedogenic oxides across all study sites. While Δ14C values of bulk MOC suggested differences in OC turnover between sites, these were not linked to differences in MOC extractability. As expected, OC contents of residues had more negative Δ14C values than extracts (an average difference between extracts and residues of 78 ± 36 ‰), suggesting that non-extractable OC is older. Δ14C values of extracts and residues were strongly correlated and proportional to Δ14C values of bulk MOC but were not dependent on mineralogy. Neither MOC extractability nor differences in Δ14C values between extracts and residues changed with depth along soil profiles, where declining Δ14C values might indicate slower OC turnover in deeper soils. Thus, the 14C depth gradients in the studied soils were not explained by increasing stability of organic–mineral associations with soil depth. Although H2O2 removed 90 ± 8 % of the MOC, the Δ14C values of oxidized OC (on average −50 ± 110 ‰) were similar to those of OC extracted with NaF–NaOH (−51 ± 122 ‰), but oxidation residues (−345 ± 227 ‰) were much more depleted in 14C than residues of the NaF–NaOH extraction (−130 ± 121 ‰). Accordingly, both chemical treatments removed OC from the same continuum, and oxidation residues were older than extraction residues because more OC was removed. In contrast to the NaF–NaOH extractions, higher contents of pedogenic oxides slightly increased the oxidation resistance of MOC, but this higher H2O2 resistance did not coincide with more negative Δ14C values of MOC nor its oxidation residues. Therefore, none of the applied chemical fractionation schemes were able to explain site-specific differences in Δ14C values. Our results indicate that total MOC was dominated by OC interactions with pedogenic oxides rather than clay minerals, as we detected no difference in bond strength between clay-rich and clay-poor sites. This suggests that site-specific differences in Δ14C values of bulk MOC and depth profiles are driven by the accumulation and exchange rates of OC at mineral surfaces.

Watershed dissolved organic carbon transport: a modeling approach combining water travel times and reactivity continuum

2020 ◽  
Author(s):  
Giulia Grandi ◽  
Enrico Bertuzzo
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Dissolved Organic Carbon ◽  
Transport Model ◽  
Terrestrial Ecosystems ◽  
Riverine Ecosystems ◽  
Doc Concentration ◽  
Tightly Coupled ◽  
Reactivity Continuum ◽  
Carbon Degradation

<p>Although their contribution was neglected in the past, inland waters play a significant role in the carbon cycle and affect CO<sub>2</sub> global balance. Streams and rivers are now considered not only as pipelines but as active reactors able to collect and transform carbon from terrestrial ecosystems trough drainage, erosion, deposition and respiration. Quantifying the transfer of carbon from the terrestrial to the riverine ecosystems is thus of crucial importance to fully appreciate carbon cycle at the watershed, regional and global scales. Such transfer is largely controlled by the processes occurring in the critical zone where the carbon and water cycles are tightly coupled. Previous studies investigated how hydrological drivers can affect Dissolved Organic Carbon (DOC) concentration in streams highlighting an hysteretic and unsteady behavior for the DOC-discharge relationship. In this study, we focus on the drainage flux from hillslopes to stream and river networks during rainfall events combining a transport model for water and a model of carbon degradation in soil. Using high-frequency records of chloride and DOC in Plynlimon catchments (UK), we employ the recently developed StorAge Selection (SAS) theory to evaluate water travel time and its partition as evapotranspiration, discharge and storage. We combine this approach with the reactivity continuum  theory to model  carbon degradation along the flow paths using a gamma-distribution as probability density function of the quality. The developed model can thus predict not only the flux of DOC released from hillslopes but also its quality (i.e. lability). We also show how the variability of the DOC-discharge relationship can partially be explained by hydrological fluctuations.</p>

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