Soil microbial functioning and organic carbon storage: can complex timber tree stands mimic natural forests?

Conversion of natural forest to anthropogenic land use systems (LUS) often leads to considerable loss of carbon, however, proper management of these LUS may reverse the trend. A study was conducted in a semi-deciduous forest zone of Côte d'Ivoire to assess soil microbial functioning and soil organic carbon (SOC) stocks in varying tree stands, and to determine whether complex tree stands can mimic the natural forest in terms of these soil attributes. Tree plantations studied were monocultures of teak (Tectona grandis) and full-sun cocoa (Theobroma cacao L.), and a mixture of four tree species (MTS) with Tectona grandis, Gmelina arborea, Terminalia ivoriensis and Terminalia superba. An adjacent natural forest was considered as the reference. Each of these LUS had five replicate stands where soil (0-10 cm depth) samples were taken for physico-chemical parameters and microbial biomass-C (MBC), microbial activities, MBC/SOC ratio and metabolic quotient (qCO₂). SOC and total N stocks were also calculated. The C mineralization rate (mg C-CO₂ kg^-1) and mineral N concentration (mg kg^-1) drastically declined in the monocultures of cocoa (154.9 ± 29.3 and 49.8 ± 9.8, respectively) and teak (179.6 ± 27.1 and 54.1 ± 7.3) compared to the natural forest (258.4 ± 21.9 and 108.7 ± 12). However, values in MTS (194.7 ± 24.6 and 105.4 ± 7.4) were not significantly different from those in the natural forest. Similarly, SOC stocks in MTS (28.8 ± 1.9 Mg ha^-1) were not significantly different from those recorded in the natural forest (32.9 ± 1.7 Mg ha^-1) whereas teak (25.4 ± 1.7 Mg ha^-1) and cocoa (23.1 ± 3.4 Mg ha^-1) exhibited significantly lower values. Despite the acidic soil and recalcitrant litter conditions, increased MBC/SOC ratio and decreased qCO₂ were recorded in the monocrops, suggesting a probable increase in the fungi/bacteria ratio. The complex MTS stand was found to mimic the natural forest in terms of soil microbial activity and organic status, due to the provision of a diversity of litter quality, which may serve as a basis for developing a climate smart timber system in West and Central Africa.

[Assessment of the spatial memory in patients suffering from generalized epilepsy]

This study aimed to assess eventual disturbances of spatial memory in patients suffering from generalized epilepsy in order to better grasp these patients' attitudes so as to keep track their neuropsychological accompaniments. 70 patients presenting generalized epilepsy have taken part in spatial memory test. The test consists in studying the arrangement, the designation and the evocation of images in the course of spatial disposition learning test. Over the 70 patients, 51% of the cases passed the test with performances similar to witnesses, 29% passed the test with late learning. Eventually 20% of patients failed to the test.

Enhanced protection against Ebola virus mediated by an improved adenovirus-based vaccine

Background

The Ebola virus is transmitted by direct contact with bodily fluids of infected individuals, eliciting death rates as high as 90% among infected humans. Currently, replication defective adenovirus-based Ebola vaccine is being studied in a phase I clinical trial. Another Ebola vaccine, based on an attenuated vesicular stomatitis virus has shown efficacy in post-exposure treatment of nonhuman primates to Ebola infection. In this report, we modified the common recombinant adenovirus serotype 5-based Ebola vaccine expressing the wild-type ZEBOV glycoprotein sequence from a CMV promoter (Ad-CMVZGP). The immune response elicited by this improved expression cassette vector (Ad-CAGoptZGP) and its ability to afford protection against lethal ZEBOV challenge in mice was compared to the standard Ad-CMVZGP vector.

Methodology/Principal Findings

Ad-CMVZGP was previously shown to protect mice, guinea pigs and nonhuman primates from an otherwise lethal challenge of Zaire ebolavirus. The antigenic expression cassette of this vector was improved through codon optimization, inclusion of a consensus Kozak sequence and reconfiguration of a CAG promoter (Ad-CAGoptZGP). Expression of GP from Ad-CAGoptZGP was substantially higher than from Ad-CMVZGP. Ad-CAGoptZGP significantly improved T and B cell responses at doses 10 to 100-fold lower than that needed with Ad-CMVZGP. Additionally, Ad-CAGoptZGP afforded full protections in mice against lethal challenge at a dose 100 times lower than the dose required for Ad-CMVZGP. Finally, Ad-CAGoptZGP induced full protection to mice when given 30 minutes post-challenge.

Conclusions/Significance

We describe an improved adenovirus-based Ebola vaccine capable of affording post-exposure protection against lethal challenge in mice. The molecular modifications of the new improved vaccine also translated in the induction of significantly enhanced immune responses and complete protection at a dose 100 times lower than with the previous generation adenovirus-based Ebola vaccine. Understanding and improving the molecular components of adenovirus-based vaccines can produce potent, optimized product, useful for vaccination and post-exposure therapy.

Effect of mycorrhization on the accumulation of rishitin and solavetivone in potato plantlets challenged with Rhizoctonia solani

The effect of colonization with the vesicular-arbuscular mycorrhizal fungus Glomus etunicatum on the content of rishitin and solavetivone was determined in potato plants cv. Goldrush challenged with Rhizoctonia solani. Mycorrhization stimulated significantly the accumulation of both phytoalexins in roots of plantlets challenged with R. solani but did not influence phytoalexin levels in non-challenged plantlet roots. No accumulation of solavetivone or rishitin was detected in shoots. In Petri dish bioassays, rishitin and solavetivone inhibited mycelial growth of R. solani.

Effect of two vesicular-arbuscular mycorrhizal fungi on the growth of micropropagated potato plantlets and on the extent of disease caused by Rhizoctonia solani

Two micropropagated potato cultivars, Goldrush and LP89221, were inoculated into sowing trays with either Glomus etunicatum or G. intraradices in a greenhouse. After 2 weeks, plantlets were transplanted into pots and roots were challenged 7 days later with Rhizoctonia solani. At different times after R. solani infection, disease severity, mortality rate, root colonization levels, various growth parameters, and shoot mineral content were evaluated. In Goldrush, only inoculation with G. etunicatum led to a significant reduction in disease severity, ranging between 60.2% and 71.2%, on both shoot and crown. This decrease was not observed in LP89221. Compared with the control plantlets, inoculation of Goldrush with G. etunicatum or G. intraradices reduced significantly the mortality rate by 77% and 26%, respectively, whereas vesicular-arbuscular mycorrhizal (VAM) fungi did not significantly influence the mortality rate in LP89221. In Goldrush, inoculation with G. etunicatum significantly increased shoot fresh weight, root dry weight and the number of tubers produced per plant, whereas G. intraradices only significantly increased the number of tubers. Tuber and root fresh weights of both potato cultivars were significantly reduced by R. solani infection. However, R. solani-infected plantlets of both Goldrush and LP89221, inoculated with G. etunicatum, produced significantly greater tuber fresh weight than non-VAM plantlets. In R. solani-infected plantlets of Goldrush but not LP89221, G. etunicatum and G. intraradices increased root fresh weight by approximately 140.3% and 76.5%, respectively, compared with non-VAM plants. The potato cultivars Goldrush and LP89221 responded differently to VAM fungal inoculation and to R. solani infection in terms of shoot mineral content.