Organisms that use ammonium as the sole nitrogen source discriminate between [(15)N] and [(14)N] ammonium. This selectivity leaves an isotopic signature in their biomass that depends on the external concentration of ammonium. To dissect how differences in discrimination arise molecularly, we examined a wild-type (WT) strain of Escherichia coli K12 and mutant strains with lesions affecting ammon...

Stable isotope analysis has been used as a technique to analyse fisheries food webs for a quarter of a century, and remains the principal method for determining energy and nutrient pathways from primary producers to consumers in aquatic ecosystems. Carbon isotope analysis has been used to distinguish autotrophs at the base of inshore and offshore fisheries food webs. The combination of nitrogen...

We examine the ecology of reddish-gray mouse lemurs from three habitats at Beza Mahafaly Special Reserve using focal follows and stable carbon and nitrogen isotope data. Focal observations indicate dietary differences among habitats as well as sexes and seasons. Both sexes consume more arthropods during the rainy season but overall, females consume more sugar-rich exudates and fruit than males,...

Divergent selection and adaptive divergence can increase phenotypic diversification amongst populations and lineages. Yet adaptive divergence between different environments, habitats or niches does not occur in all lineages. For example, the colonization of freshwater environments by ancestral marine species has triggered adaptive radiation and phenotypic diversification in some taxa but not in...

Biodiversity is well studied in ecology and the concept has been developed to include traits of species, rather than solely taxonomy, to better reflect the functional diversity of a system. The deep sea provides a natural environmental gradient within which to study changes in different diversity metrics, but traits of deep-sea fish are not widely known, hampering the application of functional ...

In ecology, stable isotope labelling is commonly used for tracing material transfer in trophic interactions, nutrient budgets and biogeochemical processes. The main assumption in this approach is that the enrichment with a heavy isotope has no effect on the organism growth and metabolism. This assumption is, however, challenged by theoretical considerations and experimental studies on kinetic i...

Quantification of stable isotope tracers has revealed the dynamic state of living tissues. A new form of imaging mass spectrometry quantifies isotope ratios in domains much smaller than a cubic micron, enabling measurement of cell turnover and metabolism with stable isotope tracers at the single-cell level with a methodology we refer to as multi-isotope imaging mass spectrometry. In a first-in-...

Deuteriumand N-induced isotope effects on H and C chemical shifts of the imino moiety of 16 trans-N-benzylideneaniline (tBA) isotopomers were determined and analysed. These effects appear to be a sensitive probe of molecular conformation and its changes. All determined deuterium isotope effects on the imino-proton are small and negative and are spread in the range from −0.88 ppb in 4-H-tBA to −...

We combine path-integral Monte Carlo methods with high-quality potential energy surfaces to compute equilibrium isotope effects in a variety of systems relevant to 'clumped' isotope analysis and isotope geochemistry, including CO2, N2O, methane, and propane. Through a systematic study of heavy-atom isotope-exchange reactions, we quantify and analyze errors that arise in the widely used Urey mod...