Questions persist about interpreting isotope ratios of bound and mobile soil water pools, particularly relative to clay content and extraction conditions. Interactions between pools and resulting extracted water isotope composition are presumably related to soil texture, yet few studies have manipulated the bound pool to understand its influence on soil water processes. Using a series of drying and spiking experiments, we effectively labelled bound and mobile water pools in soils with varying clay content. Soils were first vacuum dried to remove residual water, which was then replaced with heavy isotope-enriched water prior to oven drying and spiking with heavy isotope-depleted water. Water was extracted via centrifugation or cryogenic vacuum distillation (at four temperatures) and analysed for oxygen and hydrogen isotope ratios via isotope ratio mass spectrometry. Water from centrifuged samples fell along a mixing line between the two added waters but was more enriched in heavy isotopes than the depleted label, demonstrating that despite oven drying, a residual pool remains and mixes with the mobile water. Soils with higher clay + silt content appeared to have a larger bound pool. Water from vacuum distillation samples have a significant temperature effect, with high temperature extractions yielding progressively more heavy isotope-enriched values, suggesting that Rayleigh fractionation occurred at low temperatures in the vacuum line. By distinctly labelling bound and mobile soil water pools, we detected interactions between the two that were dependent on soil texture. Although neither extraction method appeared to completely extract the combined bound and mobile (total water) pool, centrifugation and high temperature cryogenic vacuum distillations were comparable for both δ 2 H and δ 18 O of soil water isotope ratios. K E Y W O R D Sclay mineralogy, extraction, methods, soil texture, soil water, stable isotopes, two water world hypothesis

UMAMIT24 and UMAMIT25 are expressed in distinct seed tissue during Arabidopsis embryogenesis, and are both involved in amino acid transfer to the seed.

No abstract

The stable isotopic signatures of biophilic elements, such as carbon, nitrogen, and sulfur, exhibited in animal soft body parts are excellent indicators for evaluating the pathways of energy and food sources. Thioautotrophic and methanotrophic nutrition prevailed in deep-sea hydrothermal vent and methane seep areas results in sulfide-sulfur and methanecarbon isotopic ratios. In this study, we reevaluated the carbon, nitrogen, and sulfur isotope compositions of animals taken from deep-sea hydrothermal vents and methane seep areas in order to understand the detailed pathways of energy and food sources for the habitants. The results showed that most animals collected from sediment-starved hydrothermal areas rely on thioautotrophic nutrition, using hydrogen sulfide dissolved in venting fluids as the sole primary energy source. On the other hand, animals from sediment-covered hydrothermal vent and cold seep fields show some variations in energy sources, of both hydrothermal and microbial origins. Sediment-covered areas tend to be enriched in biomass and diversity relative to sediment-starved areas. The results suggest that fluid discharged through sediments to the seafloor are strongly affected by subsurface microbial processes and result in increased biomass and diversity of the seafloor animal community.

Background: Currently, much is unknown about the taxonomic diversity and the mechanisms of methane metabolism in the Florida Everglades ecosystem. The Loxahatchee National Wildlife Refuge is a section of the Florida Everglades that is almost entirely unstudied in regard to taxonomic profiling. This short report analyzes the metagenome of soil samples from this Refuge to investigate the predominant taxa, as well as the abundance of genes involved in environmentally significant metabolic pathways related to methane production (nitrogen fixation and dissimilatory sulfite reduction). Methods: Shotgun metagenomic sequencing using the Illumina platform was performed on 17 soil samples from four different sites within the Loxahatchee National Wildlife Refuge, and underwent quality control, assembly, and annotation. The soil from each sample was tested for water content and concentrations of organic carbon and nitrogen. Results: The three most common phyla of bacteria for every site were Actinobacteria, Acidobacteria, and Proteobacteria; however, there was variation in relative phylum composition. The most common phylum of Archaea was Euryarchaeota for all sites. Alpha and beta diversity analyses indicated significant congruity in taxonomic diversity in most samples from Sites 1, 3, and 4 and negligible congruity between Site 2 and the other sites. Shotgun metagenomic sequencing revealed the presence of biogeochemical biomarkers of particular interest (e.g., mrcA, nifH, and dsrB) within the samples. The normalized abundances of mcrA, nifH, and dsrB exhibited a positive correlation with nitrogen concentration and water content, and a negative correlation with organic carbon concentration. Conclusion: This Everglades soil metagenomic study allowed examination of wetlands biological processes and showed expected correlations between measured organic constituents and prokaryotic gene frequency. Additionally, the taxonomic profile generated gives a basis for the diversity of prokaryotic microbial life throughout the Everglades.