Tracing metabolic pathways of lipid biosynthesis in ectomycorrhizal fungi from position‐specific 13C‐labelling in glucose

Six position‐specific 13C‐labelled isotopomers of glucose were supplied to the ectomycorrhizal fungi Suillus pungens and Tricholoma flavovirens. From the resulting distribution of 13C among fungal PLFAs, the overall order and contribution of each glucose atom to fatty acid 13C enrichment was: C6 (∼31%) \u3e C5 (∼25%) \u3e C1 (∼18%) \u3e C2 (∼18%) \u3e C3 (∼8%) \u3e C4 (∼1%). These data were used to parameterize a metabolic model of the relative fluxes from glucose degradation to lipid synthesis. Our data revealed that a higher amount of carbon is directed to glycolysis than to the oxidative pentose phosphate pathway (60% and 40% respectively) and that a significant part flows through these pathways more than once (73%) due to the reversibility of some glycolysis reactions. Surprisingly, 95% of carbon cycled through glyoxylate prior to incorporation into lipids, possibly to consume the excess of acetyl‐CoA produced during fatty acid turnover. Our approach provides a rigorous framework for analysing lipid biosynthesis in fungi. In addition, this approach could ultimately improve the interpretation of isotopic patterns at natural abundance in field studies

Thioarsenic Species Associated with Increased Arsenic Release during Biostimulated Subsurface Sulfate Reduction

Introduction of acetate into groundwater at the Rifle Integrated Field Research Challenge (Rifle, CO) has been used for biostimulation aimed at immobilizing uranium. While a promising approach for lowering groundwater-associated uranium, a concomitant increase in soluble arsenic was also observed at the site. An array of field data was analyzed to understand spatial and temporal trends in arsenic release and possible correlations to speciation, subsurface redox conditions, and biogeochemistry. Arsenic release (up to 9 μM) was strongest under sulfate reducing conditions in areas receiving the highest loadings of acetate. A mixture of thioarsenate species, primarily trithioarsenate and dithioarsenate, were found to dominate arsenic speciation (up to 80%) in wells with the highest arsenic releases; thioarsenates were absent or minor components in wells with low arsenic release. Laboratory batch incubations revealed a strong preference for the formation of multiple thioarsenic species in the presence of the reduced precursors arsenite and sulfide. Although total soluble arsenic increased during field biostimulation, the termination of sulfate reduction was accompanied by recovery of soluble arsenic to concentrations at or below prestimulation levels. Thioarsenic species can be responsible for the transient mobility of sediment-associated arsenic during sulfidogenesis and should be considered when remediation strategies are implemented in sulfate-bearing, contaminated aquifers

End-member compositions of hydrothermal fluids from SONNE cruise SO253

Calculated end-member compositions of hydrothermal fluids (for samples that have at least ≥ 85 % end-member) from Haungaroa, Brothers Upper Caldera and NW Caldera Wall, Kermadec intraoceanic arc. Ambient background seawater concentrations are given for comparison

Rare Earth Element and yttrium (REY) concentrations from SONNE cruise SO253

Rare Earth Element and yttrium (REY) concentrations measured with ICP-MS in hydrothermal fluids from the Kermadec intraoceanic arc. Seawater from 1000 m water depth, values for SW are * 100 (SW data from Alibo and Nozaki (1999; doi:10.1016/S0016-7037(98)00279-8))

Overview of all fluid samples collected during SONNE cruise SO253

Overview of all fluid samples collected during SO253 along the Kermadec intraoceanic arc together with parameters that were analyzed directly onboard.Fe were determined by a visual Fe CHEMets© field kit

Major, minor and trace element concentrations from SONNE cruise SO253

Major, minor and trace element concentrations measured with ICP-OES, ICP-MS and data for SO42- in hydrothermal fluids from the Kermadec intraoceanic arc

Comparison of Brothers hydrothermal fluid composition

Comparison of Brothers hydrothermal fluid composition collected by de Ronde et al. (2011; doi:10.1007/s00126-011-0345-8) with data collected during this study. In this study, only samples taken with IGT and Major samplers with end-member concentrations greater than 50% are shown. The three samples from the Upper Caldera Site are not included within this data set