scholarly journals Competitive ligand exchange reveals time dependant changes in the reactivity of Hg–dissolved organic matter complexes

2012 ◽  
Vol 9 (6) ◽  
pp. 495 ◽  
Author(s):  
Carrie L. Miller ◽  
Liyuan Liang ◽  
Baohua Gu
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Ligand Exchange ◽  
Aquatic Systems ◽  
Time Dependent ◽  
Exchange Reactions ◽  
Oak Ridge ◽  
Strength Of Interaction ◽  
Competitive Ligand Exchange ◽  
Over Time

Environmental contextMercury, a globally important pollutant, undergoes transformations in the environment to form methylmercury that is toxic to humans. Naturally occurring dissolved organic matter is a controller in these transformations, and we demonstrate that its strength of interaction with mercury is time dependent. These changes in complexation with dissolved organic matter are likely to affect mercury’s reactivity in aquatic systems, thereby influencing how mercury is methylated and bioaccumulated. AbstractMercury interactions with dissolved organic matter (DOM) are important in aquatic environments but the kinetics of Hg binding to and repartitioning within the DOM remain poorly understood. We examined changes in Hg–DOM complexes using glutathione (GSH) titrations, coupled with stannous-reducible Hg measurements during Hg equilibration with DOM. In laboratory prepared DOM solutions and in water from a Hg-contaminated creek, a fraction of the Hg present as Hg–DOM complexes did not react to GSH addition. This unreactive Hg fraction increased with time from 13 % at 1 h to 74 % after 48 h of equilibration with a Suwannee River DOM. In East Fork Poplar Creek water in Oak Ridge, Tennessee, ~58 % of the DOM-complexed Hg was unreactive with GSH 1 h after the sample was collected. This time-dependent increase in unreactive Hg suggests that Hg forms stronger complexes with DOM over time. Alternatively the DOM-complexed Hg may become more sterically protected from the ligand exchange reactions, as the binding environment changes within the DOM over time. These results have important implications to understanding Hg transformations in the natural environment, particularly in contaminated aquatic systems due to non-equilibrium interactions between Hg and DOM.

Characterisation of dissolved organic matter in Parisian urban aquatic systems: predominance of hydrophilic and proteinaceous structures

2010 ◽  
Vol 106 (1) ◽  
pp. 89-106 ◽  
Author(s):  
B. Pernet-Coudrier ◽  
G. Varrault ◽  
M. Saad ◽  
J. P. Croue ◽  
M.-F. Dignac ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Aquatic Systems

scholarly journals Rhizobactin B is the preferred siderophore by a novel Pseudomonas isolate to obtain iron from dissolved organic matter in peatlands

BioMetals ◽  
2020 ◽  
Vol 33 (6) ◽  
pp. 415-433
Author(s):  
Stefan Kügler ◽  
Rebecca E. Cooper ◽  
Johanna Boessneck ◽  
Kirsten Küsel ◽  
Thomas Wichard
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Ligand Exchange ◽  
High Resolution Mass Spectrometry ◽  
Iron Acquisition ◽  
Water Extract ◽  
Resonance Spectroscopy ◽  
Biological Processes ◽  
Polycarboxylic Acid ◽  
Chelating Compounds

AbstractBacteria often release diverse iron-chelating compounds called siderophores to scavenge iron from the environment for many essential biological processes. In peatlands, where the biogeochemical cycle of iron and dissolved organic matter (DOM) are coupled, bacterial iron acquisition can be challenging even at high total iron concentrations. We found that the bacterium Pseudomonas sp. FEN, isolated from an Fe-rich peatland in the Northern Bavarian Fichtelgebirge (Germany), released an unprecedented siderophore for its genus. High-resolution mass spectrometry (HR-MS) using metal isotope-coded profiling (MICP), MS/MS experiments, and nuclear magnetic resonance spectroscopy (NMR) identified the amino polycarboxylic acid rhizobactin and a novel derivative at even higher amounts, which was named rhizobactin B. Interestingly, pyoverdine-like siderophores, typical for this genus, were not detected. With peat water extract (PWE), studies revealed that rhizobactin B could acquire Fe complexed by DOM, potentially through a TonB-dependent transporter, implying a higher Fe binding constant of rhizobactin B than DOM. The further uptake of Fe-rhizobactin B by Pseudomonas sp. FEN suggested its role as a siderophore. Rhizobactin B can complex several other metals, including Al, Cu, Mo, and Zn. The study demonstrates that the utilization of rhizobactin B can increase the Fe availability for Pseudomonas sp. FEN through ligand exchange with Fe-DOM, which has implications for the biogeochemical cycling of Fe in this peatland.

Estimation of Reactive Thiol Concentrations in Dissolved Organic Matter and Bacterial Cell Membranes in Aquatic Systems

2012 ◽  
pp. 120831120231009 ◽  
Author(s):  
Claresta Joe-Wong ◽  
Elizabeth Shoenfelt ◽  
Emily J. Hauser ◽  
Nyssa Crompton ◽  
Satish C. B. Myneni
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Bacterial Cell ◽  
Cell Membranes ◽  
Aquatic Systems

Molecular Changes in Dissolved Organic Matter After Soil Rewetting

2021 ◽  
Author(s):  
Alice Orme ◽  
Simon Benk ◽  
Markus Lange ◽  
Christian Zerfaß ◽  
Georg Pohnert ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Mass Spectrometry Analysis ◽  
Microbial Decomposition ◽  
Molecular Changes ◽  
Spectrometry Analysis ◽  
Subsurface Waters ◽  
High Production ◽  
High Concentrations ◽  
Over Time

<p>The intensity and occurrence of droughts is projected to increase due to climate change. Dried soils release high concentrations of dissolved organic matter (DOM) into subsurface waters when they are rewet, the so-called rewetting peak. To more accurately predict the role of rewetting of soils after drought on the carbon cycle in a changing climate, it is important to understand the processes behind this DOM release.</p><p>The DOM rewetting peak origin is disputed between soil organic matter (SOM) from breakdown of soil particles; accumulated root exudates; and microbial release due to a change in osmotic potential through osmolytes or cell bursting. To better understand the origin of the rewetting DOM peak, we took a rewetting series of soil water samples from different vegetation types between December 2018 and April 2019 for targeted and untargeted metabolomics. Initial results using untargeted ultrahigh-resolution mass spectrometry analysis revealed a clear temporal trend, indicating that vegetation-independent molecular changes occur following rewetting. An increase in O/C and a decrease in H/C over time was observed which is attributed to microbial decomposition, supported by a decrease in m/z over time. We also observed an increase in the content of lipidic compounds (R > 0.6) following rewetting. This indicates that cells do not burst upon rewetting and, over time, microbial activity increases, suggesting that the DOM rewetting peak is caused by a lack of decomposition, rather than a high production, of organic matter.</p>

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