Fractionation of Hydrogen Isotopes by Sulfate- and Nitrate-Reducing Bacteria.

Hydrogen atoms from water and food are incorporated into biomass during cellular metabolism and biosynthesis, fractionating the isotopes of hydrogen-protium and deuterium-that are recorded in biomolecules. While these fractionations are often relatively constant in plants, large variations in the magnitude of fractionation are observed for many heterotrophic microbes utilizing different central metabolic pathways. The correlation between metabolism and lipid δ(2)H provides a potential basis for reconstructing environmental and ecological parameters, but the calibration dataset has thus far been limited mainly to aerobes. Here we report on the hydrogen isotopic fractionations of lipids produced by nitrate-respiring and sulfate-reducing bacteria. We observe only small differences in fractionation between oxygen- and nitrate-respiring growth conditions, with a typical pattern of variation between substrates that is broadly consistent with previously described trends. In contrast, fractionation by sulfate-reducing bacteria does not vary significantly between different substrates, even when autotrophic and heterotrophic growth conditions are compared. This result is in marked contrast to previously published observations and has significant implications for the interpretation of environmental hydrogen isotope data. We evaluate these trends in light of metabolic gene content of each strain, growth rate, and potential flux and reservoir-size effects of cellular hydrogen, but find no single variable that can account for the differences between nitrate- and sulfate-respiring bacteria. The emerging picture of bacterial hydrogen isotope fractionation is therefore more complex than the simple correspondence between δ(2)H and metabolic pathway previously understood from aerobes. Despite the complexity, the large signals and rich variability of observed lipid δ(2)H suggest much potential as an environmental recorder of metabolism

Isotopic and genetic methods reveal the role of the gut microbiome in mammalian host essential amino acid metabolism.

Intestinal microbiota perform many functions for their host, but among the most important is their role in metabolism, especially the conversion of recalcitrant biomass that the host is unable to digest into bioavailable compounds. Most studies have focused on the assistance gut microbiota provide in the metabolism of carbohydrates, however, their role in host amino acid metabolism is poorly understood. We conducted an experiment on Mus musculus using 16S rRNA gene sequencing and carbon isotope analysis of essential amino acids (AAESS) to quantify the community composition of gut microbiota and the contribution of carbohydrate carbon used by the gut microbiome to synthesize AAESS that are assimilated by mice to build skeletal muscle tissue. The relative abundances of Firmicutes and Bacteroidetes inversely varied as a function of dietary macromolecular content, with Firmicutes dominating when mice were fed low-protein diets that contained the highest proportions of simple carbohydrates (sucrose). Mixing models estimated that the microbial contribution of AAESS to mouse muscle varied from less than 5% (threonine, lysine, and phenylalanine) to approximately 60% (valine) across diet treatments, with the Firmicute-dominated microbiome associated with the greatest contribution. Our results show that intestinal microbes can provide a significant source of the AAESS their host uses to synthesize structural tissues. The role that gut microbiota play in the amino acid metabolism of animals that consume protein-deficient diets is likely a significant but under-recognized aspect of foraging ecology and physiology

Dynamics of atmospheric combined inorganic nitrogen utilization in the coastal waters off North Carolina

Phytoplankton in nitrogen-depleted coastal Atlantic waters off North Carolina, USA, had a positive response to nitrogen added as rain (DIN: NO3- and NH4+) or directly as NO3- or NH4+. Increases in primary production, photopigments, and cellular protein concentrations were observed when nitrogen Limitation was alleviated. NO3- concentrations decreased faster than those of NH4+ in 670 l mesocosm experiments, performed in October 1993 and March and April 1994. Stable nitrogen isotope measurements (delta(15)N) Of particulate N typically showed similar responses to the nitrogen additions. The delta(15)N decreased as the different DIN sources, having delta(15)N values near 0 parts per thousand, were incorporated into cell biomass. The smallest changes (about 1 parts per thousand) occurred in the Delta(15)N (delta(15)N(initial) - delta(15)N(final)) from nitrate additions. A greater shift of about 2 parts per thousand was observed with added DIN from rain, even though delta(15)N Of total DIN was similar. Ammonium additions resulted in the largest difference from the control, about 6 to 7 parts per thousand. This fractionation is indicative of isotopic fractionation during enzymatic incorporation and active transport of ammonium into the cells. In parallel incubations, C-14-bicarbonate was added along with rain in addition to all N additions and controls. Subcellular C-14-labeled fractions from these samples showed a short-term response to nitrogen additions and included an increase in the low molecular weight fraction after the first light incubation (from dawn to dusk). Carbon was allocated into protein after a 24 h period that encompassed the night incubation

Characterization of pysio-chemical properties of novel one stop chemical method in preparations of copper nanofluids and possible explanations

Nanofluid is a dilute suspension containing particles in nanometer sized which are dispersed in the base fluid like ethylene glycol or water. Nanofluid is one of the crucial discovery in modern science which found to be having better thermal properties compared with conventional fluids like water or ethylene glycol thus makes it ideal to be applied and utilized in many areas in heat transfer area such as cooling, utilized as fluid for heat echangers and etc. Besides, the nanofluid with the improved thermal properties could solve the problem faced by various industries in the area of heat transfer. For example, in the semiconductor industry, the needs of superior cooling coolant are very crucialJn this paper, presents about preparation of copper nanofluid using novel one stop chemical method by reducing copper sulphate pentahydrate using reduction agent which is sodium hypophosphite in ethylene glycol as base fluids. The obtained nanofluid by using this novel one stop method is more stable besides cheaper and faster compared with two stop method whereby in the two step method, the production of the nanoparticles and the nanofluids are isolated. The process of drying, storage and transportation of the nanoparticles that takes place in two step method have cause the agglomeration and sedimentation of the nanofluids. As the result, the agglomeration could cause the settlement and clogging in the microchannel besides reduce the thermal conductivity. Therefore in the novel one stop method the production of the nanoparticles and the nanofluids are combined and not separated to avoid the process of drying, storage and transportation of nanoparticles. Meanwhile the nanofluid that obtained were analyzed using Transmission Electron Microscopy (TEM), UV-Vis Spectrophotometer, Viscometer and Fourier Transform Infared Spectroscopy (FTIR). The effect and influences of pH and dilution to the reaction rate and properties of nanofluid were also investigated

Rainfall Stimulation of Primary Production in Western Atlantic Ocean Waters: Roles of Different Nitrogen Sources and Co-Limiting Nutrients

Using shipboard bioassays, we examined the roles rainfall, individual and combined nutrients play in accelerating primary production in coastal, Gulf Stream and pelagic (Sargasso Sea) locations in the North Atlantic Ocean off North Carolina, USA, from 1993 to 1995. Photosynthetic CO2 fixation and net chlorophyll a (chl a) production were measured In replicated bioassays to assess individual and combined impacts of different constituents of atmospheric deposition, including natural rainfall, a synthetic rain mix, dissolved inorganic nitrogen (DIN; NH4+ ,NO3-), dissolved organic nitrogen (DON; urea),phosphorus (PO43-) and iron (as EDTA-chelated and unchelated FeCl3).Natural rainfall and DIN additions most often stimulated CO2 fixation and chl a production, but frequencies and magnitudes of biostimulation, relative to controls, varied between these indicators. Spatial differences in the types and magnitudes of stimulation were also observed. When added in equimolar amounts, NH4+ was, at times, more stimulatory than NO3-. The NO3- stimulation was significantly enhanced by Fe-EDTA. Urea was marginally stimulatory at the coastal location. PO43- was never stimulatory. Fe-EDTA and EDTA by themselves stimulated production only at the offshore locations, suggesting increased Fe limitation with increasing distance from land. Synthetic rain, which contained both sources of DIN, but not Fe, generally proved less stimulatory per unit N than natural rainfall. Results indicate a broad sensitivity of these waters to N additions, which in the case of NO3- are enhanced by Fe-EDTA. At all locations, the high level of stimulation of primary production attributable to natural rain may be due to the supply of both DIN and CO-limiting nutrients (e.g. Fe), contributing to the eutrophication potential of waters downwind of urban, industrial and agricultural emissions

Fractionation of Hydrogen Isotopes by Sulfate- and Nitrate-Reducing Bacteria

Hydrogen atoms from water and food are incorporated into biomass during cellular metabolism and biosynthesis, fractionating the isotopes of hydrogen—protium and deuterium—that are recorded in biomolecules. While these fractionations are often relatively constant in plants, large variations in the magnitude of fractionation are observed for many heterotrophic microbes utilizing different central metabolic pathways. The correlation between metabolism and lipid δ^2H provides a potential basis for reconstructing environmental and ecological parameters, but the calibration dataset has thus far been limited mainly to aerobes. Here we report on the hydrogen isotopic fractionations of lipids produced by nitrate-respiring and sulfate-reducing bacteria. We observe only small differences in fractionation between oxygen- and nitrate-respiring growth conditions, with a typical pattern of variation between substrates that is broadly consistent with previously described trends. In contrast, fractionation by sulfate-reducing bacteria does not vary significantly between different substrates, even when autotrophic and heterotrophic growth conditions are compared. This result is in marked contrast to previously published observations and has significant implications for the interpretation of environmental hydrogen isotope data. We evaluate these trends in light of metabolic gene content of each strain, growth rate, and potential flux and reservoir-size effects of cellular hydrogen, but find no single variable that can account for the differences between nitrate- and sulfate-respiring bacteria. The emerging picture of bacterial hydrogen isotope fractionation is therefore more complex than the simple correspondence between δ^2H and metabolic pathway previously understood from aerobes. Despite the complexity, the large signals and rich variability of observed lipid δ^2H suggest much potential as an environmental recorder of metabolism

Chemical Evidence for Cell Wall Lignification and the Evolution of Tracheids in Early Devonian Plants

Anatomically preserved land plant fossils from the Lower Devonian Rhynie Chert contain conducting tissues with cells that range from dark-colored, elongated cells without secondary wall thickenings to tracheids similar to those of extant tracheophytes. A suite of tissue-specific microanalytical techniques was used to assess lignification in fossils of Aglaophyton, Rhynia, and Asteroxylon. Isotope ratio mass spectrometry provides millimeter-scale resolution of carbon isotopic abundances, whereas soft X-ray carbon (1s) spectromicroscopy provides micrometer-scale resolution of the preservation of organic molecular functionality. The isotopic and organic chemistry of Rhynie Chert plants indicates that the earliest vascular thickenings were probably unlignified and that cell wall lignification may have first appeared in the outer cortex. Only in more derived plants, it seems, was lignin deposited in conducting cells to produce the true tracheids seen today in vascular plants.Organismic and Evolutionary Biolog