How mutualisms arise in phytoplankton communities: building eco-evolutionary principles for aquatic microbes.

Extensive sampling and metagenomics analyses of plankton communities across all aquatic environments are beginning to provide insights into the ecology of microbial communities. In particular, the importance of metabolic exchanges that provide a foundation for ecological interactions between microorganisms has emerged as a key factor in forging such communities. Here we show how both studies of environmental samples and physiological experimentation in the laboratory with defined microbial co-cultures are being used to decipher the metabolic and molecular underpinnings of such exchanges. In addition, we explain how metabolic modelling may be used to conduct investigations in reverse, deducing novel molecular exchanges from analysis of large-scale data sets, which can identify persistently co-occurring species. Finally, we consider how knowledge of microbial community ecology can be built into evolutionary theories tailored to these species' unique lifestyles. We propose a novel model for the evolution of metabolic auxotrophy in microorganisms that arises as a result of symbiosis, termed the Foraging-to-Farming hypothesis. The model has testable predictions, fits several known examples of mutualism in the aquatic world, and sheds light on how interactions, which cement dependencies within communities of microorganisms, might be initiated.EK is grateful for funding from UKERC and EU FP7 DEMA project, grant agreement no. 309086. KEH was supported by the UK Biotechnology and Biological Sciences Research Council (BBSRC), grant BB/I013164/1.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1111/ele.12615

Chemical sputtering yields of carbon based materials at high ion flux densities

Graphite and advanced carbon fiber composites (CFC) are widely used inside the vacuum vessel of magnetic fusion devices. However, erosion by chemical sputtering via hydrocarbon formation might limit their application as target material in future machines like ITER. The first systematic study of the chemical erosion of graphite and different CFCs (including a silicon-doped one) as a function of ion flux density in the range of 1.4 × 1021–5 × 1022 m-2 s-1was performed in the plasma generator PSI-1. The results of three different analysis methods agree within about 40%. No differences in the chemical erosion yields between hydrogen and deuterium exposures are found for the various materials. In contrast, the erosion yields differ up to a factor of two for the different CFC-materials. In general, the chemical sputtering yields decrease with increasing ion flux density Γ according to Γ-0.6reaching levels below 1% at the highest fluxes. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) show preferred erosion in the area between the carbon fibers

Recent results of H-mode studies on asdex

In a comparative study of various confinement regimes the H-mode demonstrated the best performance. Confinement enhancement factors (above ITER 89-P L-mode scaling) in the range of 1.6 fH 2.8 have been achieved with values depending on the divertor configuration, the wall condition, ELM behaviour and the plasma ion spicies. Long-pulse H-phases, withELMs, of up to 3.5s with constant confinement time, recycling and impurity characteristics are archived. H* -mode operation is possible without a loss of current scaling at qa values as low as 2.2. The B-limit is the same with and without ELMs. Murakami parameters are similar in H-and L-modes