The Corrosion Behavior of Carbon Steel in Sulfide Aqueous Media at 30 degrees C

International audienceIn this paper, we studied the effect of sulfide ions on the corrosion behavior of carbon steel to simulate the geological disposal of high-level radioactive waste. In geological storage conditions, sulfidogenic environment was sustained by sulfate-reducing bacteria. Corrosion tests were conducted in systems in a controlled atmosphere of 5% H-2/N-2. Batch experiments were conducted at 30A degrees C for 1 month with steel coupons immersed in Na2S solutions. The structural characterization of the corrosion products was investigated by scanning electron microscope/energy dispersive x-ray spectroscopy, confocal micro-Raman spectrometry, and x-ray diffraction. In the absence of sulfide ion, a magnetite (Fe3O4) corrosion product layer was formed on steel surface while in the presence of sulfide ions we observed the formation of a poorly crystallized irons sulfide at low-sulfide concentration (1 mg/L) and a solid adherent pyrrhotite layer at higher sulfide concentration (5-15 mg/L). The strong drop in steel corrosion rate with sulfide concentration was revealed and related to the formation of well-crystallized pyrrhotite

Expansion of Signal Transduction Pathways in Fungi by Extensive Genome Duplication

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordPlants and fungi use light and other signals to regulate development, growth, and metabolism. The fruiting bodies of the fungus Phycomyces blakesleeanus are single cells that react to environmental cues, including light, but the mechanisms are largely unknown [1]. The related fungus Mucor circinelloides is an opportunistic human pathogen that changes its mode of growth upon receipt of signals from the environment to facilitate pathogenesis [2]. Understanding how these organisms respond to environmental cues should provide insights into the mechanisms of sensory perception and signal transduction by a single eukaryotic cell, and their role in pathogenesis. We sequenced the genomes of P. blakesleeanus and M. circinelloides and show that they have been shaped by an extensive genome duplication or, most likely, a whole-genome duplication (WGD), which is rarely observed in fungi [3-6]. We show that the genome duplication has expanded gene families, including those involved in signal transduction, and that duplicated genes have specialized, as evidenced by differences in their regulation by light. The transcriptional response to light varies with the developmental stage and is still observed in a photoreceptor mutant of P. blakesleeanus. A phototropic mutant of P. blakesleeanus with a heterozygous mutation in the photoreceptor gene madA demonstrates that photosensor dosage is important for the magnitude of signal transduction. We conclude that the genome duplication provided the means to improve signal transduction for enhanced perception of environmental signals. Our results will help to understand the role of genome dynamics in the evolution of sensory perception in eukaryotes.The work by the US Department of Energy Joint Genome Institute, a DOE Office of Science User Facility, is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The project was supported by European funds (European Regional Development Fund, ERDF), the Spanish Ministerio de Economía y Competitividad (BIO2005-25029-E, BIO2015-67148-R), and the Regional Government (Junta de Andalucía, P06-CVI-01650) to L.M.C.; Conacyt (Mexico) (FORDECYT-2012-02-193512) to A.H.-E.; the US National Science Foundation (MCB-0920581) to A.I.; and the Czech Science Foundation (13-33039S) to M.E