3 research outputs found
Advanced Solvent Based Methods for Molecular Characterization of Soil Organic Matter by High-Resolution Mass Spectrometry
Soil organic matter (SOM), a complex,
heterogeneous mixture of
above and belowground plant litter and animal and microbial residues
at various degrees of decomposition, is a key reservoir for carbon
(C) and nutrient biogeochemical cycling in soil based ecosystems.
A limited understanding of the molecular composition of SOM limits
the ability to routinely decipher chemical processes within soil and
accurately predict how terrestrial carbon fluxes will respond to changing
climatic conditions and land use. To elucidate the molecular-level
structure of SOM, we selectively extracted a broad range of intact
SOM compounds by a combination of different organic solvents from
soils with a wide range of C content. Our use of electrospray ionization
(ESI) coupled with Fourier transform ion cyclotron resonance mass
spectrometry (FTICR MS) and a suite of solvents with varying polarity
significantly expands the inventory of the types of organic molecules
present in soils. Specifically, we found that hexane is selective
for lipid-like compounds with very low O/C ratios (<0.1); water
(H<sub>2</sub>O) was selective for carbohydrates with high O/C ratios;
acetonitrile (ACN) preferentially extracts lignin, condensed structures,
and tannin polyphenolic compounds with O/C > 0.5; methanol (MeOH)
has higher selectivity toward compounds characterized with low O/C
< 0.5; and hexane, MeOH, ACN, and H<sub>2</sub>O solvents increase
the number and types of organic molecules extracted from soil for
a broader range of chemically diverse soil types. Our study of SOM
molecules by ESI FTICR MS revealed new insight into the molecular-level
complexity of organics contained in soils. We present the first comparative
study of the molecular composition of SOM from different ecosystems
using ultra high-resolution mass spectrometry
Data_Sheet_1_Microbial Interactions With Dissolved Organic Matter Drive Carbon Dynamics and Community Succession.docx
<p>Knowledge of dynamic interactions between natural organic matter (NOM) and microbial communities is critical not only to delineate the routes of NOM degradation/transformation and carbon (C) fluxes, but also to understand microbial community evolution and succession in ecosystems. Yet, these processes in subsurface environments are usually studied independently, and a comprehensive view has been elusive thus far. In this study, we fed sediment-derived dissolved organic matter (DOM) to groundwater microbes and continually analyzed microbial transformation of DOM over a 50-day incubation. To document fine-scale changes in DOM chemistry, we applied high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and soft X-ray absorption spectroscopy (sXAS). We also monitored the trajectory of microbial biomass, community structure and activity over this time period. Together, these analyses provided an unprecedented comprehensive view of interactions between sediment-derived DOM and indigenous subsurface groundwater microbes. Microbial decomposition of labile C in DOM was immediately evident from biomass increase and total organic carbon (TOC) decrease. The change of microbial composition was closely related to DOM turnover: microbial community in early stages of incubation was influenced by relatively labile tannin- and protein-like compounds; while in later stages the community composition evolved to be most correlated with less labile lipid- and lignin-like compounds. These changes in microbial community structure and function, coupled with the contribution of microbial products to DOM pool affected the further transformation of DOM, culminating in stark changes to DOM composition over time. Our study demonstrates a distinct response of microbial communities to biotransformation of DOM, which improves our understanding of coupled interactions between sediment-derived DOM, microbial processes, and community structure in subsurface groundwater.</p
Formularity: Software for Automated Formula Assignment of Natural and Other Organic Matter from Ultrahigh-Resolution Mass Spectra
Ultrahigh
resolution mass spectrometry, such as Fourier transform
ion cyclotron resonance mass spectrometry (FT ICR MS), can resolve
thousands of molecular ions in complex organic matrices. A Compound
Identification Algorithm (CIA) was previously developed for automated
elemental formula assignment for natural organic matter (NOM). In
this work, we describe software Formularity with a user-friendly interface
for CIA function and newly developed search function Isotopic Pattern
Algorithm (IPA). While CIA assigns elemental formulas for compounds
containing C, H, O, N, S, and P, IPA is capable of assigning formulas
for compounds containing other elements. We used halogenated organic
compounds (HOC), a chemical class that is ubiquitous in nature as
well as anthropogenic systems, as an example to demonstrate the capability
of Formularity with IPA. A HOC standard mix was used to evaluate the
identification confidence of IPA. Tap water and HOC spike in Suwannee
River NOM were used to assess HOC identification in complex environmental
samples. Strategies for reconciliation of CIA and IPA assignments
were discussed. Software and sample databases with documentation are
freely available