| 1. |
- Patriarca, Claudia, et al.
(författare)
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Investigating the Ionization of Dissolved Organic Matter by Electrospray
- 2020
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 92:20, s. 14210-14218
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Tidskriftsartikel (refereegranskat)abstract
- Electrospray ionization (ESI) operating in the negative mode coupled to high-resolution mass spectrometry is the most popular technique for the characterization of dissolved organic matter (DOM). The vast molecular heterogeneity and the functional group diversity of this complex mixture prevents the efficient ionization of the organic material by a single ionization source, so the presence of uncharacterized material is unavoidable. The extent of this poorly ionizable pool of carbon is unknown, is presumably variable between samples, and can only be assessed by the combination of analysis with a uniform detection method. Charged aerosol detection (CAD), whose response is proportional to the amount of nonvolatile material and is independent from the physicochemical properties of the analytes, is a suitable candidate. In this study, a fulvic acid mixture was fractionated and analyzed by high-pressure liquid chromatography–mass spectrometry in order to investigate the polarity and size distributions of highly and poorly ionizable material in the sample. Additionally, DOM samples of terrestrial and marine origins were analyzed to evaluate the variability of these pools across the land–sea aquatic continuum. The relative response factor values indicated that highly ionizable components of aquatic DOM mixtures are more hydrophilic and have lower molecular weight than poorly ionizable components. Additionally, a discrepancy between the samples of terrestrial and marine origins was found, indicating that marine samples are better represented by ESI than terrestrial samples, which have an abundant portion of hydrophobic poorly ionizable material.
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| 2. |
- Patriarca, Claudia, et al.
(författare)
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Character and environmental lability of cyanobacteria-derived dissolved organic matter
- 2021
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 66:2, s. 496-509
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Tidskriftsartikel (refereegranskat)abstract
- Autotrophic dissolved organic matter (DOM) is central to the carbon biogeochemistry of aquatic systems, and the full complexity of autotrophic DOM has not been extensively studied, particularly by high-resolution mass spectrometry (HRMS). Terrestrial DOM tends to dominate HRMS studies in freshwaters due to the propensity of such compounds to ionize by negative mode electrospray, and possibly also because ionizable DOM produced by autotrophy is decreased to low steady-state concentrations by heterotrophic bacteria. In this study, we investigated the character of DOM produced by the widespread cyanobacteria Microcystis aeruginosa using high-pressure liquid chromatography—electrospray ionization—high-resolution mass spectrometry. M. aeruginosa produced thousands of detectable compounds in axenic culture. These compounds were chromatographically resolved and the majority were assigned to aliphatic formulas with a broad polarity range. We found that the DOM produced by M. aeruginosa was highly susceptible to removal by heterotrophic freshwater bacteria, supporting the hypothesis that this autotroph-derived organic material is highly labile and accordingly only seen at low concentrations in natural settings.
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| 3. |
- Patriarca, Claudia, 1986-
(författare)
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Characterisation of natural dissolved organic matter with liquid chromatography and high resolution mass spectrometry
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dissolved organic matter (DOM) is one of the most heterogeneous and complex mixture on Earth. DOM plays a crucial role in biogeochemical processes on the global scale and it is essential to sustain and regulate the biological processes in aquatic ecosystems. DOM originates from a multitude of biological, physical and chemical transformations, leading to its phenomenal chemical diversity. In order to understand and predict its effect on the global carbon cycle, an intimate characterization at molecular level is necessary. The investigation of the extraordinary complexity of the DOM mixture represents a compelling challenge for analytical chemistry. The focus of this thesis was the development of methods for the characterization of DOM in natural waters. High resolution mass spectrometry (HRMS), was combined with high pressure liquid chromatography (HPLC) and electrospray ionization (ESI), to investigate the chemical diversity of DOM. The first study demonstrated that cutting-edge techniques (such as the Fourier-transform ion cyclotron resonance mass spectrometer - FTICR-MS), are not indispensable to disclose essential information on the DOM molecular composition, in fact the Orbitrap mass analyser is a suitable alternative for the analysis of complex natural mixtures. In the second study, the potential benefits offered by the online coupling of HPLC and HRMS instruments were explored, revealing significant advantages in terms of analysis time, achievable information and versatility of the method. The advantages of online separation were further confirmed in the third study, focused on the characterization of autochthonous labile DOM. Chromatographically resolved profiles emerged from the bulk-DOM, allowing the monitoring of labile autochthonous components in presence of heterotrophic bacteria. Despite the advantages achieved by the application of online separation, a strong limiting factor in DOM characterization is the ESI source, suitable only for the analysis of the DOM fraction susceptible to ionization. In the last study, the extent of the DOM material prone to ionization was estimated, revealing the occurrence of an extensive portion of the material resistant to routinely employed ESI approach. The full characterization of DOM is still an open challenge and the combination of multiple techniques is fundamental to unravel is extreme intricacy.
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| 4. |
- Reyer, Henry, et al.
(författare)
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Mineral Phosphorus Supply in Piglets Impacts the Microbial Composition and Phytate Utilization in the Large Intestine
- 2021
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Ingår i: Microorganisms. - : MDPI. - 2076-2607. ; 9:6
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Tidskriftsartikel (refereegranskat)abstract
- A sufficient supply of phosphorus (P) to pigs in livestock farming is based on the optimal use of plant-based phytate and mineral P supplements to ensure proper growth processes and bone stability. However, a high P supplementation might bear the risk of higher environmental burden due to the occurrence of excess P and phytate degradation products in manure. In this context, the intestinal microbiota is of central importance to increase P solubility, to employ non-mineral P by the enzymatic degradation of phytate, and to metabolize residual P. A feeding experiment was conducted in which piglets were fed diets with different P levels, resulting in three groups with low, medium (covering requirements), and high concentrations of available P. Samples from caecum and colon digesta were analysed for microbial composition and phytate breakdown to estimate the microbial contribution to metabolize P sources. In terms of identified operational taxonomic units (OTU), caecum and colon digesta under the three feeding schemes mainly overlap in their core microbiome. Nevertheless, different microbial families correlate with increased dietary P supply. Specifically, microbes of Desulfovibrionaceae, Pasteurellaceae, Anaerovoracaceae, and Methanobacteriaceae were found significantly differentially abundant in the large intestine across the dietary treatments. Moreover, members of the families Veillonellaceae, Selenomonadaceae, and Succinivibrionaceae might contribute to the observed phytate degradation in animals fed a low P diet. In this sense, the targeted manipulation of the intestinal microbiota by feeding measures offers possibilities for the optimization of intestinal phytate and P utilization.
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| 5. |
- Rydin, Emil, et al.
(författare)
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Contrasting distribution and speciation of sedimentary organic phosphorus among different basins of the Baltic Sea
- 2023
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Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 68:4, s. 767-779
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Tidskriftsartikel (refereegranskat)abstract
- Recycling of phosphorus (P) from deoxygenated sediments perpetuates eutrophic conditions in parts of the Baltic Sea. Sedimentary organic P is a major source of dissolved P to the water column, but also a sink for permanent P burial. The mechanisms behind these two pathways are, however, largely unknown. Using new methods, we determined P in DNA and phospholipids, which are both found in all organisms. We also identified inositol phosphates that are particularly important in eukaryotes. Sediment cores were collected from contrasting basins in the Baltic Sea to study their relative contribution to the total P pool. We found high DNA-P/phospholipid-P ratios in surface sediments from the Bothnian Bay and Bothnian Sea. However, these ratios were low throughout profiles in euxinic Baltic Proper sediments. The elevated ratios present in sediments overlain by oxic bottom waters might indicate the presence of a microbial community stimulated by bioturbation, whereas the low DNA-P/phospholipid-P ratios in Baltic Proper sediments likely indicate an energy-limited microbial community, typical to the "deep biosphere" environment. Inositol-P was almost absent in euxinic Baltic Proper sediments that had a low total P amount compared to those in the other basins. We suggest that variability in the composition of sedimentary microbial communities among the Baltic Sea basins might cause differences in organic P forms that in turn affects its turnover.
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