Studies of microbial sulfate reduction have suggested that the magnitude of sulfur isotope fractionation varies with sulfate concentration. Small apparent sulfur isotope fractionations preserved in Archean rocks have been interpreted as suggesting Archean sulfate concentrations of <200 μm, while larger fractionations thereafter have been interpreted to require higher concentrations. In this wor...

Microbial sulfate reduction (MSR) utilizes sulfate as an electron acceptor and produces sulfide that is depleted in heavy isotopes of sulfur relative to starting sulfate. The fractionation of S-isotopes is commonly used to trace the biogeochemical cycling of sulfur in nature, but a mechanistic understanding of factors that control the range of isotope fractionation is still lacking. This thesis...

The carbon isotope fractionation associated with nocturnal malic acid synthesis in Kalanchoë daigremontiana and Bryophyllum tubiflorum was calculated from the isotopic composition of carbon-4 of malic acid, after appropriate corrections. In the lowest temperature treatment (17 degrees C nights, 23 degrees C days), the isotope fractionation for both plants is -4 per thousand (that is, malate is ...

Kinetic isotope effects related to the breaking of chemical bonds drive sulfur isotope fractionation during dissimilatory sulfate reduction (DSR), whereas oxygen isotope fractionation duringDSR is dominated by exchange between intercellular sulfur intermediates and water. We use a simplified biochemical model for DSR to explore how a kinetic oxygen isotope effect may be expressed. We then explo...

Compound-specific isotope analysis (CSIA) is a promising approach for tracking biotransformation of organic pollutants, but isotope fractionation associated with aromatic oxygenations is only poorly understood. We investigated the dioxygenation of a series of nitroaromatic compounds to the corresponding catechols by two enzymes, namely, nitrobenzene and 2-nitrotoluene dioxygenase (NBDO and 2NTD...

Microbial sulfate reduction can impart strong sulfur isotope fractionation by preferentially using the lighter 32SO2! 4 over the heavier 34SO 4 . The magnitude of fractionation depends on a number of factors, including ambient concentrations of sulfate and electron donors. Sulfur isotope compositions in sedimentary rocks thus facilitate reconstruction of past environmental conditions, such as s...

Copper isotopic composition is altered in cancerous compared to healthy tissues. However, the rationale for this difference is yet unknown. As a model of Cu isotopic fractionation, we monitored Cu uptake in Saccharomyces cerevisiae, whose Cu import is similar to human. Wild type cells are enriched in 63Cu relative to 65Cu. Likewise, 63Cu isotope enrichment in cells without high-affinity Cu tran...

13C/(12)C and D/H stable isotope fractionation during aerobic degradation was determined for Pseudomonas putida strain mt-2, Pseudomonas putida strain F1, Ralstonia pickettii strain PKO1, and Pseudomonas putida strain NCIB 9816 grown with toluene, xylenes, and naphthalene. Different types of initial reactions used by the respective bacterial strains could be linked with certain extents of stabl...

Citation: Meyerink S, Ellwood MJ, Maher WA and Strzepek R (2017) Iron Availability Influences Silicon Isotope Fractionation in Two Southern Ocean Diatoms (Proboscia inermis and Eucampia antarctica) and a Coastal Diatom (Thalassiosira pseudonana). Front. Mar. Sci. 4:217. doi: 10.3389/fmars.2017.00217 Iron Availability Influences Silicon Isotope Fractionation in Two Southern Ocean Diatoms (Probos...

Recent findings based on the oxygen isotope ratios of tree trunk cellulose indicate that the temperature of biomass production in biomes ranging from boreal to subtropical forests converge to an average leaf temperature of 21.4°C. The above conclusion has been drawn under the assumption that biochemically related isotopic fractionations during cellulose synthesis are not affected by temperature...