Climate change threatens food security by affecting the productivity of major cereal crops. To date, agroclimatic risk projections through indicators have focused on expected hazards exposure during ...the crop's current vulnerable seasons, without considering the non-stationarity of their phenology under evolving climatic conditions. We propose a new method for spatially classifying agroclimatic risks for wheat, combining high-resolution climatic data with a wheat's phenological model. The method is implemented for French wheat involving three GCM-RCM model pairs and two emission scenarios. We found that the precocity of phenological stages allows wheat to avoid periods of water deficit in the near future. Nevertheless, in the coming decades the emergence of heat stress and increasing water deficit will deteriorate wheat cultivation over the French territory. Projections show the appearance of combined risks of heat and water deficit up to 4 years per decade under the RCP 8.5 scenario. The proposed method provides a deep level of information that enables regional adaptation strategies: the nature of the risk, its temporal and spatial occurrence, and its potential combination with other risks. It's a first step towards identifying potential sites for breeding crop varieties to increase the resilience of agricultural systems.
The seed microbiota is currently of great interest in the scientific community since seed germination is a critical stage in plant life cycle. Some seed endophytic bacteria could be commonly found in ...seeds of hyperaccumulating plants and may confer them an evolutionary advantage over non-hyperaccumulating plants when confronted to biotic or abiotic stress. This study focuses on the endophytic bacterial diversity of a wide diversity of metal hyperaccumulating and non-hyperaccumulating plants (93 seed samples from Mediterranean regions, Oceania, South-East Asia) to reveal the core endophyte communities specific of hyperaccumulating plants. The rather low richness of the seed bacterial communities found in all seeds suggest that a sub-population of specialized endophytic strains is able to colonize seeds and survive. The factor that shapes the diversity of those bacterial communities was first the botanical family and secondly the hyperaccumulation trait of the host plants. Based on the taxonomic affiliation, we revealed that the Brassicales had 1349 OTUs that were specific to them and the Asterales 204 OTUs, independently of their metal accumulation strategy. Nonetheless, a set of 12 OTUs were shared by the seeds of all the hyperaccumulators independently of the taxonomic order of the plants (among Asterales and Brassicales) and could be considered as a ‘stable’ core microbiome. Those OTUs identified as Luteibacter, Alphaproteobacteria unclassified, Sphingopyxis, Alishewanella, bacteria unclassified, Heliimonas, Aeromicrobium, Proteobacteria unclassified, Xanthomonadales unclassified and Micromonosporaceae unclassified may constitute an endophytic bacterial core with PGP traits. Further studies are needed to extend our knowledge of the possible role played by those bacteria.
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•Bacterial diversity of 93 seed populations is described using DNA metabarcoding.•Botanical family shapes the diversity of the bacterial communities.•A stable core microbiome is composed of 12 OTUs specific to hyperaccumulators.
Aims
Phytoremediation of soil contaminated by trace elements is a technology using plants and microorganisms to sequester, inactivate, or extract contaminants from the soil. The assemblage formed by ...the partnership between plants and microorganisms is referred to as the plant holobiont concept. Among holobiont microorganisms, endophytes are associated with the plant at its earliest growth stage and are localized inside plant tissues. While plant tissues shelter endophytic microbial communities, mutualistic endophytes have shown a potential for plant growth promotion that will deeply and durably benefit the plant holobiont. In this review, we describe the state-of-the-art knowledge of the endophytes’ role in plant growth promotion and the prospects for phytoremediation technologies.
Results
Mutualistic symbionts have been demonstrated to improve plant growth, germination and yield. Indeed, they improve plant nutrition, increase plant resistance to bio-aggressors and stimulate plant metabolite productions. Research has shown that endophytes improve plant performance especially under extreme conditions such as drought, nitrogen deficiency, salinity and exposition to metal phytotoxicity. Endophyte inoculation has shown potential for plant growth promotion and has increased metal translocation in hyperaccumulator shoots by mitigating stresses from contaminated and naturally metal-rich soils.
Conclusions
Endophytes have demonstrated their potential to enhance the plant’s physiological status under metallic stress, the growth of both roots and shoots, as well as increasing metal uptake in the shoot biomass of a wide diversity of hyperaccumulating plants. Endophyte-assisted phytoremediation is a promising technology for the remediation of polluted or naturally metal-rich soils.
This meta-analysis compared amiodarone with placebo and class Ic drugs for the cardioversion of recent-onset atrial fibrillation (AF), defined as lasting less than seven days.
Despite the lack of ...trials that support its efficacy convincingly, amiodarone is widely used for conversion of recent-onset AF.
We searched Medline and EMBASE databases, as well as the Cochrane Controlled Trials Register for randomized trials on recent-onset AF comparing amiodarone to placebo or class Ic drugs. Data were combined according to a fixed effect model. The primary end point was the rate of conversion at 24 h. To study time-dependency of the drugs, efficacy at 1 to 2 h, 3 to 5 h, 6 to 8 h, and at 24 h was analyzed.
We found six studies randomizing amiodarone versus placebo (595 patients) and seven studies versus class Ic drugs (579 patients). There was no significant difference between amiodarone and placebo at 1 to 2 h, but significant efficacy was found after 6 to 8 h (relative risk RR 1.23, p = 0.022) and at 24 h (RR 1.44, p < 0.001). Efficacy with amiodarone was inferior to class Ic drugs for up to 8 h (RR 0.67, p < 0.001) but no difference was seen at 24 h (RR 0.95, p = 0.50). There were no major adverse effects.
Amiodarone is superior to placebo for cardioversion of AF, and even though the onset of conversion is delayed, its efficacy is similar at 24 h compared with class Ic drugs. These results favor amiodarone as a reasonable alternative for patients with recent AF in whom class Ic and other, more rapidly acting antiarrhythmic drugs cannot be used.
Abstract One of the challenges of agromining is the adoption of more environmentally‐friendly solutions to improve plant biomass yields and Ni concentrations in plants. Here, we focused on four ...sustainable solutions for optimizing nickel phytoextraction by the hyperaccumulator Odontarrhena chalcidica : a biostimulant, another biostimulant/plant defense stimulator, artificial root exudates, and a biodegradable metal chelator. Their effects on the growth and physiology of O. chalcidica , on Ni phytoextraction capacity, on physicochemical soil characteristics, and on the diversity of rhizosphere and endophytic bacteria were compared to a conventional mineral fertilizer. A 5‐month pot experiment was carried out with O. chalcidica growing on an ultramafic soil. Element concentrations in both soil and plant were measured. Moreover, numerous compounds were analyzed (photosynthetic pigments, malondialdehyde, flavonoids, free amino acids, and starch). We also characterized rhizosphere and endophytic bacterial communities associated with this hyperaccumulator. Biostimulants appeared to be a promising way of improving Ni concentration in shoots and plant biomass production, and showed a positive effect on bacterial richness and diversity. In contrast, our experiments did not show that artificial exudates and mineral fertilizer had a positive effect on Ni phytoextraction. Finally, the biodegradable chelator had no significant effect. The use of sustainable amendments into a Ni agromining system improved both plant biomass and Ni yields, in comparison to mineral fertilization. Thus, improving agromining by replacing mineral fertilizers would be an eco‐efficient strategy.
Industrial waste dumps are rarely colonized by vegetation after they have been abandoned, indicating biological infertility. Revegetation of industrial tailings dumps is thus necessary to prevent ...wind erosion, metal leaching and has been shown to restore soil functions and ecosystem services. However, little is known about the microbial colonization and community structure of vegetated tailings following the application of restoration technologies. In this study, we investigated the rhizosphere and phyllosphere bacterial communities of a poplar tree plantation within a phytomanagement-based restoration program of a Hg-contaminated site. We used Illumina-based sequencing combined with culture-dependent approaches to describe plant-associated bacterial communities and to isolate growth-promoting bacteria (PGPB) and Hg-resistant bacteria. The genus Streptomyces was highly specific to the root community, accounting for 24.4% of the relative abundance but only representing 0.8% of the soil community, whereas OTUs from the Chloroflexi phylum were essentially detected in the soil community. Aboveground habitats were dominated by bacteria from the Deinococcus-Thermus phylum, which were not detected in belowground habitats. Leaf and stem habitats were characterized by several dominant OTUs, such as those from the phylum Firmicutes in the stems or from the genera Methylobacterium, Kineococcus, Sphingomonas and Hymenobacter in the leaves. Belowground habitats hosted more cultivable Hg-resistant bacteria than aboveground habitats and more Hg-resistant bacteria were found on the episphere than in endospheric habitats. Hg-resistant isolates exhibiting plant growth-promoting (PGP) traits, when used as inoculants of Capsicum annuum, were shown to increase its root dry biomass but not Hg concentration. The N2-fixing and Hg-resistant species Pseudomonas graminis, observed in the poplar phyllosphere, may be a key microorganism for the restoration of industrial tailings dumps.
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•Poplar habitats host Hg-resistant PGPB in a Hg-contaminated site•Bacterial communities were assessed through Illumina Miseq sequencing.•Belowground habitats host higher diversity than aboveground habitats•Chloroflexi phylum was especially abundant in the Hg-enriched soil.•Bulk soils host more cultivable Hg-resistant bacteria than other habitats
The Ministry of Health in Samoa, in partnership with the Pacific Community, successfully implemented enhanced surveillance for the high-profile Third United Nations Conference on Small Island ...Developing States held concurrently with the popular local Teuila festival during a widespread chikungunya outbreak in September 2014. Samoa's weekly syndromic surveillance system was expanded to 12 syndromes and 10 sentinel sites from four syndromes and seven sentinel sites; sites included the national hospital, four private health clinics and three national health service clinics. Daily situation reports were produced and were disseminated through PacNet (the e-mail alert and communication tool of the Pacific Public Health Surveillance Network) together with daily prioritized line lists of syndrome activity to facilitate rapid response and investigation by the Samoan EpiNet team. Standard operating procedures for surveillance and response were introduced, together with a sustainability plan, including a monitoring and evaluation framework, to facilitate the transition of the mass gathering surveillance improvements to routine surveillance. The enhanced surveillance performed well, providing vital disease early warning and health security assurance. A total of 2386 encounters and 708 syndrome cases were reported. Influenza-like illness was the most frequently seen syndrome (17%). No new infectious disease outbreaks were recorded. The experience emphasized: (1) the need for a long lead time to pilot the surveillance enhancements and to maximize their sustainability; (2) the importance of good communication between key stakeholders; and (3) having sufficient staff dedicated to both surveillance and response.
Aims
Phytomining relies on the use of metal hyperaccumulating plants growing on ultramafic soils. Such soils, naturally enriched with nickel, have drawn the attention of the scientific community for ...several decades, yet little is known about the effect of this metal on the structure and composition of the rhizosphere and endospheric bacterial communities of hyperaccumulators. This work aimed to investigate the impact of a Ni concentration gradient on soil's physicochemical properties and on the composition of the rhizosphere and endophytic bacterial communities of
Odontarrhena chalcidica
.
Methods
We characterized the bacterial communities associated with
O. chalcidica
growing in controlled conditions on an ultramafic soil with various levels of nickel contamination obtained by spiking the soil with nickel sulfate.
Results
An increase in the available nickel in soil induced changes in the dominant bacterial genera in the communities of the rhizosphere soil and in the root and shoot endosphere. This increase in available nickel also entailed changes in the relative abundance of the predicted functions, for the rhizosphere and root endospheric bacterial communities. In addition, topological features of the bacterial networks seemed to indicate that at an intermediate level of nickel contamination, two coexisting bacterial sub-communities were in competition, one adapted to “low” soil nickel content and the other to higher nickel content, while the bacterial communities were more stable at the lowest and the highest nickel soil contamination levels. Our results revealed shifts in the microbial community's structure and functions, depending of the gradient of soil nickel availability in the soil.
Mercury (Hg) is a highly toxic metal with no known biological function, and it can be highly bioavailable in terrestrial ecosystems. Although fungi are important contributors to a number of soil ...processes including plant nutrient uptake and decomposition, little is known about the effect of Hg on fungi. Fungi accumulate the largest amount of Hg and are the organisms capable of the highest bioaccumulation of Hg. While referring to detailed mechanisms in bacteria, this mini-review emphasizes the progress made recently on this topic and represents the first step towards a better understanding of the mechanisms underlying Hg tolerance and accumulation in fungal species and hence on the role of fungi within the Hg cycle at Hg-contaminated sites.
Key points
•
The fungal communities are more resilient than bacterial communities to Hg exposure.
• The exposure to Hg is a threat to microbial soil functions involved in both C and nutrient cycles.
• Fungal (hyper)accumulation of Hg may be important for the Hg cycle in terrestrial environments.
• Understanding Hg tolerance and accumulation by fungi may lead to new remediation biotechnologies.
The aim of the present study is to deepen the current understanding of the microbial communities at two poplar phytomanagement sites to reveal the environmental factors that drive the abundance, ...diversity and composition of microbial communities. A soil analysis revealed that the two soils displayed contrasting physico-chemical characteristics, with significant lower pH and higher Cd, Zn and Mn CaCl2-extractable fractions at Leforest site, compared with Pierrelaye site. The fungal and bacterial community profiles in the poplar roots and soils were assessed through Illumina MiSeq sequencing. Diversity indices and β-diversity measures illustrated that the root microbial communities were well separated from the soil microbial communities at both sites. A detailed study of the fungal composition showed that Ascomycota dominated the overall fungal communities on poplar soil, the root samples at Pierrelaye, and the unplanted soil at the experimental sites. Conversely, Basidiomycota accounted for a much higher percentage of the fungal community in poplar root samples from the Leforest site. The root bacterial communities were dominated by Alphaproteobacteria and Actinobacteria, and the soil samples were dominated by Alphaproteobacteria and Acidobacteria. The occurrence and dominance of the ectomycorrhizal community at Leforest but not at Pierrelaye is the major feature of our data set. Overall, ectomycorrhizal root symbionts appeared to be highly constrained by soil characteristics at the phytomanagement sites. Our data support the view that mycorrhizal inoculation is needed in highly stressed and nutrient-poor environments.
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•Two anthropospheric soils displayed contrasting physico-chemical characteristics.•Fungal and bacterial communities were assessed through Illumina Miseq sequencing.•Root microbial communities were well separated from soil microbial communities.•Ascomycota dominated the fungal community in unplanted soils and Pierrelaye site.•The ectomycorrhizal (mostly Basidiomycota) community dominated at Leforest.
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