Interactive and Single Effects of Ectomycorrhiza Formation and Bacillus cereus on Metallothionein MT1 Expression and Phytoextraction of Cd and Zn by Willows

Single and joint ectomycorrhizal (+ Hebeloma mesophaeum) and bacterial (+ Bacillus cereus) inoculations of willows (Salix viminalis) were investigated for their potential and mode of action in the promotion of cadmium (Cd) and zinc (Zn) phytoextraction. Dual fungal and bacterial inoculations promoted the biomass production of willows in contaminated soil. Single inoculations either had no effect on the plant growth or inhibited it. All inoculated willows showed increased concentrations of nutritional elements (N, P, K and Zn) and decreased concentrations of Cd in the shoots. The lowest biomass production and concentration of Cd in the willows (+ B. cereus) were combined with the strongest expression of metallothioneins. It seems that biotic stress from bacterial invasion increased the synthesis of these stress proteins, which responded in decreased Cd concentrations. Contents of Cd and Zn in the stems of willows were combination-specific, but were always increased in dual inoculated plants. In conclusion, single inoculations with former mycorrhiza-associated B. cereus strains decreased the phytoextraction efficiency of willows by causing biotic stress. However, their joint inoculation with an ectomycorrhizal fungus is a very promising method for promoting the phytoextraction of Cd and Zn through combined physiological effects on the plant

Studies on the production of branched-chain alcohols in engineered Ralstonia eutropha

Wild-type Ralstonia eutropha H16 produces polyhydroxybutyrate (PHB) as an intracellular carbon storage material during nutrient stress in the presence of excess carbon. In this study, the excess carbon was redirected in engineered strains from PHB storage to the production of isobutanol and 3-methyl-1-butanol (branched-chain higher alcohols). These branched-chain higher alcohols can directly substitute for fossil-based fuels and be employed within the current infrastructure. Various mutant strains of R. eutropha with isobutyraldehyde dehydrogenase activity, in combination with the overexpression of plasmid-borne, native branched-chain amino acid biosynthesis pathway genes and the overexpression of heterologous ketoisovalerate decarboxylase gene, were employed for the biosynthesis of isobutanol and 3-methyl-1-butanol. Production of these branched-chain alcohols was initiated during nitrogen or phosphorus limitation in the engineered R. eutropha. One mutant strain not only produced over 180 mg/L branched-chain alcohols in flask culture, but also was significantly more tolerant of isobutanol toxicity than wild-type R. eutropha. After the elimination of genes encoding three potential carbon sinks (ilvE, bkdAB, and aceE), the production titer improved to 270 mg/L isobutanol and 40 mg/L 3-methyl-1-butanol. Semicontinuous flask cultivation was utilized to minimize the toxicity caused by isobutanol while supplying cells with sufficient nutrients. Under this semicontinuous flask cultivation, the R. eutropha mutant grew and produced more than 14 g/L branched-chain alcohols over the duration of 50 days. These results demonstrate that R. eutropha carbon flux can be redirected from PHB to branched-chain alcohols and that engineered R. eutropha can be cultivated over prolonged periods of time for product biosynthesis.United States. Dept. of EnergyUnited States. Advanced Research Projects Agency-Energ

Le sol urbain

En milieu urbain, les différentes strates du sol constituent autant de pages d'une histoire quelquefois oubliée, dans lesquelles la trace des activités humaines est inscrite de façon parfois indélébile. En effet, le sol urbain est constitué de dépôts meubles, d'origine naturelle ou anthropique, qui contiennent un certain nombre d'ouvrages souterrains nécessaires au fonctionnement de la ville. Ces dépôts conservent, en certains endroits, les traces des occupations humaines qui permettent aux archéologues d'écrire l'histoire de la ville. Ils contiennent parfois des pollutions résultant d'activités plus récentes et sont le support de la végétation. En histoire, on distingue trois époques constitutives du sol urbain : la colonisation romaine (Ier siècle), le premier Moyen Âge (Xe siècle), la première révolution industrielle (XIXe siècle). Ces moments d'éclosion peuvent différer d'un site à l'autre de quelques décennies. L'époque gallo-romaine voit l'implantation de vastes ouvrages publics dotés de fondations profondes juxtaposées à un réseau de rues orthogonales. Dès la fin du IIIe siècle, l'occupation du sol paraît arrêtée ; elle est en fait différente (terres noires). À l'époque médiévale, la ville se redéploie à partir du castrum du IIIe siècle et gagne les fonds marécageux qui sont drainés et équipés pour l'artisanat (textile, cuir). À partir du XIVe siècle, la guerre étend les fortifications toujours plus lourdes tandis que l'artisanat transforme plus de matières organiques que minérales. L'essor industriel du XIXe siècle démantèle les fortifications, tranche et retourne le sol dont la surface devient imperméabl

Contribution of microbial activity to formation of organically bound chlorine during batch incubation of forest soil using 37Cl as a tracer

cited By 0International audienceChloride is often considered as the main chlorine form in soils. However, recent studies show that chlorine is mostly present in soils as naturally produced organically bound molecules. The relative contribution of biotic, including microbial, and abiotic processes to formation of organically bound chlorine remains poorly understood. We performed a37Cl spiking batch experiment with a forest soil incubated under abiotic and biotic conditions over two time periods to simultaneously monitor the formation of organically bound chlorine from natural and tracer chlorine. To compare biotic and abiotic conditions without biased effect of sterilization technique for abiotic control, the soil was irradiated and reinoculated or not with soil microflora. Fifteen days after microbial inoculation, the natural non-extractable organic chlorine content in the inoculated soil was significantly higher than in the sterile soil, showing that microbial activity contributed to formation of organically bound chlorine. However, no significant difference was noted between the two incubation periods. The same trend was noted for tracer chlorine, yet without a significant difference. The present study shows that chlorination is mediated by microbial activity, but there is also some indication of abiotic formation of organically bound chlorine, with a non-extractable organic tracer chlorine formation of about 6% just after spiking in abiotic conditions. © 2016 Elsevier Lt

Diapason : un systeme d'aide a la supervision des procedes continus

Available at INIST (FR), Document Supply Service, under shelf-number : RM 1054 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc