Biotransformation and detoxification of selenite by microbial biogenesis of selenium-sulfur nanoparticles.

This study combines the interaction between the toxic oxyanions selenite and selenate and the plant growth promoting bacterium Azospirillum brasilense with a comprehensive characterization of the formed selenium particles. As selenium is an essential trace element, but also toxic in high concentrations, its state of occurrence in nature is of major concern. Growth of the bacterium was affected by selenite (1-5mM) only, observable as a prolonged growth lag-phase of 3days. Subsequently, selenite reduction occurred under aerobic conditions resulting in extracellularly formed insoluble Se0 particles. Complementary studies by microscopic and spectroscopic techniques revealed the particles to be homogeneous and stable Se8-nSn structured spheres with an average size of 400nm and highly negative surface charge of -18mV in the neutral pH range. As this is the first study showing Azospirillum brasilense being able to biotransform selenite to selenium particles containing a certain amount of sulfur, even if environmental waters supplemented with selenite were used, they may significantly contribute to the biogeochemical cycling of both elements in soil as well as to their soil-plant transfer. Therefore, microbial biotransformation of selenite under certain circumstances may be used for various bio-remediation and bio-technological applications.

[Exertional heat stroke: biological survey interest]. / Intérêt de la surveillance biologique d'un patient présentant un coup de chaleur d'exercice.

We present a 27-year-old soldier exertional heat stroke case report. Clinical examination has been reassuring during hospitalization. However biological disorders, especially liver and haemostasis disturbances, show off exertional heat stroke is a serious pathology on which clinician and biologist attention must be focalized, even if evolution is the more often favourable when an adapted and rapid treatment is used.