Metabolomics as a tool for in situ study of chronic metal exposure in estuarine invertebrates.

Estuaries are subject to intense human use globally, with impacts from multiple stressors, such as metal contaminants. A key challenge is extending beyond traditional monitoring approaches to understand effects to biota and system function. To explore the metabolic effects of complex metal contaminants to sediment dwelling (benthic) fauna, we apply a multiple-lines-of-evidence approach, coupling environmental monitoring, benthic sampling, total metals analysis and targeted metabolomics.

Metabolic pathways inferred from a bacterial marker gene illuminate ecological changes across South Pacific frontal boundaries.

Global oceanographic monitoring initiatives originally measured abiotic essential ocean variables but are currently incorporating biological and metagenomic sampling programs. There is, however, a large knowledge gap on how to infer bacterial functions, the information sought by biogeochemists, ecologists, and modelers, from the bacterial taxonomic information (produced by bacterial marker gene surveys). Here, we provide a correlative understanding of how a bacterial marker gene (16S rRNA) can be used to infer latitudinal trends for metabolic pathways in global monitoring campaigns.

Can We Use Functional Genetics to Predict the Fate of Nitrogen in Estuaries?

Increasing nitrogen (N) loads present a threat to estuaries, which are among the most heavily populated and perturbed parts of the world. N removal is largely mediated by the sediment microbial process of denitrification, in direct competition to dissimilatory nitrate reduction to ammonium (DNRA), which recycles nitrate to ammonium. Molecular proxies for N pathways are increasingly measured and analyzed, a major question in microbial ecology, however, is whether these proxies can add predictive power around the fate of N.

Eukaryotic assimilatory nitrate reductase fractionates N and O isotopes with a ratio near unity.

In order to (i) establish the biological systematics necessary to interpret nitrogen (N) and oxygen (O) isotope ratios of nitrate ((15)N/(14)N and (18)O/(16)O) in the environment and (ii) investigate the potential for isotopes to elucidate the mechanism of a key N cycle enzyme, we measured the nitrate N and O isotope effects ((15)ε and (18)ε) for nitrate reduction by two assimilatory eukaryotic nitrate reductase (eukNR) enzymes. The (15)ε for purified extracts of NADPH eukNR from the fungus Aspergillus niger and the (15)ε for NADH eukNR from cell homogenates of the marine diatom Thalassiosira weissflogii were indistinguishable, yielding a mean (15)ε for the enzyme of 26.6 ± 0.