Persistent activity of aerobic methane-oxidizing bacteria in anoxic lake waters due to metabolic versatility.

Lacustrine methane emissions are strongly mitigated by aerobic methane-oxidizing bacteria (MOB) that are typically most active at the oxic-anoxic interface. Although oxygen is required by the MOB for the first step of methane oxidation, their occurrence in anoxic lake waters has raised the possibility that they are capable of oxidizing methane further anaerobically. Here, we investigate the activity and growth of MOB in Lake Zug, a permanently stratified freshwater lake.

Rhizobia-diatom symbiosis fixes missing nitrogen in the ocean.

Nitrogen (N) fixation in oligotrophic surface waters is the main source of new nitrogen to the ocean and has a key role in fuelling the biological carbon pump. Oceanic N fixation has been attributed almost exclusively to cyanobacteria, even though genes encoding nitrogenase, the enzyme that fixes N into ammonia, are widespread among marine bacteria and archaea. Little is known about these non-cyanobacterial N fixers, and direct proof that they can fix nitrogen in the ocean has so far been lacking.

Two-Dimensional Mapping of Arsenic Concentration and Speciation with Diffusive Equilibrium in Thin-Film Gels.

We present a new approach combining diffusive equilibrium in thin-film gels and spectrophotometric methods to determine the spatial distribution of arsenite, arsenate, and phosphate at submillimeter resolution. The method relies on the simultaneous deployment of three gel probes. Each retrieved gel is exposed to malachite green reagent gels differing in acidity and oxidant addition, leading to green coloration dependent on analyte speciation and concentration.

and " Velamenicoccus archaeovorus".

The phylum " Omnitrophica" (candidate division OP3) is ubiquitous in anaerobic habitats but is currently characterized only by draft genomes from metagenomes and single cells. We had visualized cells of the phylotype OP3 LiM in methanogenic cultures on limonene as small epibiotic cells. In this study, we enriched OP3 cells by double density gradient centrifugation and obtained the first closed genome of an apparently clonal OP3 cell population by applying metagenomics and PCR for gap closure.

Quantification of archaea-driven freshwater nitrification from single cell to ecosystem levels.

Deep oligotrophic lakes sustain large populations of the class Nitrososphaeria (Thaumarchaeota) in their hypolimnion. They are thought to be the key ammonia oxidizers in this habitat, but their impact on N-cycling in lakes has rarely been quantified. We followed this archaeal population in one of Europe's largest lakes, Lake Constance, for two consecutive years using metagenomics and metatranscriptomics combined with stable isotope-based activity measurements.