Surveying the endomicrobiome and ectomicrobiome of bark beetles: The case of Dendroctonus simplex.

International audienceMany bark beetles belonging to the Dendroctonus genus carry bacterial and fungal microbiota, forming a symbiotic complex that helps the insect to colonize the subcortical environment of the host tree. However, the biodiversity of those bacteria at the surface of the cuticle or inside the body parts of bark beetles is not well established. The aim of this study was to characterize the bacterial microbiome associated with the eastern larch beetle, Dendroctonus simplex, using bacterial 16S rRNA gene pyrosequencing. The ecto- and endomicrobiome and the subcortical galleries were investigated. Several bacterial genera were identified, among which Pseudomonas, Serratia and Yersinia are associated with the surface of the beetle cuticle, and genera belonging to Enterobacteriaceae and Gammaproteobacteria with the interior of the insect body. The index of dissimilarity indicates that the bacterial microbiome associated with each environment constitutes exclusive groups. These results suggest the presence of distinct bacterial microbiota on the surface of the cuticle and the interior of D. simplex body. Additionally, the bacterial diversity identified in the galleries is substantially different from the ectomicrobiome, which could indicate a selection by the insect. This study reports for the first time the identification of the eastern larch beetle microbiome

Towards the development of multifunctional molecular indicators combining soil biogeochemical and microbiological variables to predict the ecological integrity of silvicultural practices.

International audienceThe impact of mechanical site preparation (MSP) on soil biogeochemical structure in young larch plantations was investigated. Soil samples were collected in replicated plots comprising simple trenching, double trenching, mounding and inverting site preparation. Unlogged natural mixed forest areas were used as a reference. Analysis of soil nutrients, abundance of bacteria and gas exchanges unveiled no significant difference among the plots. However, inverting site preparation resulted in higher variations of gas exchanges when compared with trenching, mounding and unlogged natural forest. A combination of the biological and physicochemical variables was used to define a multifunctional classification of the soil samples into four distinct groups categorized as a function of their deviation from baseline ecological conditions. According to this classification model, simple trenching was the approach that represented the lowest ecological risk potential at the microsite level. No relationship was observed between MSP method and soil bacterial community structure as assessed by high-throughput sequencing of bacterial 16S rRNA gene; however, indicator genotypes were identified for each multifunctional soil class. This is the first identification of multifunctional molecular indicators for baseline and disturbed ecological conditions in soil, demonstrating the potential of applied microbial ecology to guide silvicultural practices and ecological risk assessment

Strategies of exploitation of mammalian reservoirs by Bartonella species

Numerous mammal species, including domestic and wild animals such as ruminants, dogs, cats and rodents, as well as humans, serve as reservoir hosts for various Bartonella species. Some of those species that exploit non-human mammals as reservoir hosts have zoonotic potential. Our understanding of interactions between bartonellae and reservoir hosts has been greatly improved by the development of animal models for infection and the use of molecular tools allowing large scale mutagenesis of Bartonella species. By reviewing and combining the results of these and other approaches we can obtain a comprehensive insight into the molecular interactions that underlie the exploitation of reservoir hosts by Bartonella species, particularly the well-studied interactions with vascular endothelial cells and erythrocytes

Identification of Plasmodium falciparum var1CSA and var2CSA domains that bind IgM natural antibodies

Malaria in pregnancy is responsible for maternal anaemia, low-birth-weight babies and infant deaths. Plasmodium falciparum infected erythrocytes are thought to cause placental pathology by adhering to host receptors such as chondroitin sulphate A (CSA). CSA binding infected erythrocytes also bind IgM natural antibodies from normal human serum, a process that may facilitate placental adhesion or promote immune evasion. The parasite ligands that mediate placental adhesion are thought to be members of the variant erythrocyte surface antigen family P. falciparum erythrocyte membrane protein 1 (PfEMP1), encoded by the var genes. Two var gene sub-families, var1CSA and var2CSA, have been identified as parasite CSA binding ligands and are leading candidates for a vaccine to prevent pregnancy-associated malaria. We investigated whether these two var gene subfamilies implicated in CSA binding are also the molecules responsible for IgM natural antibody binding. By heterologous expression of domains in COS-7 cells, we found that both var1CSA and var2CSA PfEMP1 variants bound IgM, and in both cases the binding region was a DBL epsilon domain occurring proximal to the membrane. None of the domains from a control non-IgM-binding parasite (R29) bound IgM when expressed in COS-7 cells. These results show that PfEMP1 is a parasite ligand for non-immune IgM and are the first demonstration of a specific adhesive function for PfEMP1 epsilon type domains

In Vivo Detection of Succinate by Magnetic Resonance Spectroscopy as a Hallmark of SDHx Mutations in Paraganglioma

International audiencePurpose: Germline mutations in genes encoding mitochon-drial succinate dehydrogenase (SDH) are found in patients with paragangliomas, pheochromocytomas, gastrointestinal stromal tumors, and renal cancers. SDH inactivation leads to a massive accumulation of succinate, acting as an oncometabolite and which levels, assessed on surgically resected tissue are a highly specific biomarker of SDHx-mutated tumors. The aim of this study was to address the feasibility of detecting succinate in vivo by magnetic resonance spectroscopy. Experimental Design: A pulsed proton magnetic resonance spectroscopy (1 H-MRS) sequence was developed, optimized, and applied to image nude mice grafted with Sdhb À/À or wild-type chromaffin cells. The method was then applied to patients with paraganglioma carrying (n ¼ 5) or not (n ¼ 4) an SDHx gene mutation. Following surgery, succinate was measured using gas chromatography/mass spectrometry, and SDH protein expression was assessed by immunohistochemistry in resected tumors. Results: A succinate peak was observed at 2.44 ppm by 1 H-MRS in all Sdhb À/À-derived tumors in mice and in all paragangliomas of patients carrying an SDHx gene mutation, but neither in wild-type mouse tumors nor in patients exempt of SDHx mutation. In one patient, 1 H-MRS results led to the identification of an unsus-pected SDHA gene mutation. In another case, it helped define the pathogenicity of a variant of unknown significance in the SDHB gene. Conclusions: Detection of succinate by 1 H-MRS is a highly specific and sensitive hallmark of SDHx mutations. This non-invasive approach is a simple and robust method allowing in vivo detection of the major biomarker of SDHx-mutated tumors. Clin Cancer Res; 22(5); 1120–9. Ó2015 AACR

Interaction of Copper-Based Nanoparticles to Soil, Terrestrial, and Aquatic Systems: Critical Review of the State of the Science and Future Perspectives

In the past two decades, increased production and usage of metallic nanoparticles (NPs) has inevitably increased their discharge into the different compartments of the environment, which ultimately paved the way for their uptake and accumulation in various trophic levels of the food chain. Due to these issues, several questions have been raised on the usage of NPs in everyday life and has become a matter of public health concern. Among the metallic NPs, Cu-based NPs have gained popularity due to their cost-effectiveness and multifarious promising uses. Several studies in the past represented the phytotoxicity of Cu-based NPs on plants. However, comprehensive knowledge is still lacking. Additionally, the impact of Cu-based NPs on soil organisms such as agriculturally important microbes, fungi, mycorrhiza, nematode, and earthworms are poorly studied. This review article critically analyses the literature data to achieve a more comprehensive knowledge on the toxicological profile of Cu-based NPs and increase our understanding of the effects of Cu-based NPs on aquatic and terrestrial plants as well as on soil microbial communities. The underlying mechanism of biotransformation of Cu-based NPs and the process of their penetration into plants has also been discussed herein. Overall, this review could provide valuable information to design rules and regulations for the safe disposal of Cu-based NPs into a sustainable environment

Diversité des espèces de Bartonella circulant au sein d’une population de rongeurs sylvatiques dans une zone de forêt suburbaine, la forêt de Sénart

Gram-negative bacteria belonging to the genus Bartonella are facultative intracellular bacteria which can infect the red blood cells of a wide variety of mammal species. To date, 33 Bartonella have been validly described including 20 of them identified in rodents, of which some are associated with human case of illness. Studies from many parts of the world indicate that rodent populations carry high diversity of Bartonella species with high rates of prevalence. Several factors linked to host, arthropod vector and the environment in which they have evolved have shaped and influence this diversity. The purpose of this PhD project was to better understand some of these factors by studying the Bartonella strains circulating within a community of sylvatic rodents in a French suburban forest, the Sénart forest. Firstly, based on an accurate and robust phylogeny, we identified 63 Bartonella genotypes affiliated to 3 known Bartonella species (B. taylorii, B. grahamii and B. doshiae), frequently recovered from woodland rodents in Europe, and to one new Bartonella species in proximity to B. rochalimae. We demonstrated that the majority of genotypes obtained here are highly specific either bank voles or wood mice. Despite the physical barrier created by host specificity, we observed exchanges of genetic material between Bartonella strains associated to bank voles and strains specific to wood mice, suggesting that these strains can co-habit within the arthropod vector. Secondly, we assessed, using statistical tools, the impact of Borrelia afzelii on prevalence and diversity of Bartonella strains within a population of field voles, using statistical analysis, we observed that these two bacteria can be found in conjunction, but they do not appear to interact.Les bactéries du genre Bartonella sont des alpha-proteobacteria intracellulaires facultatives, capables d'infecter les érythrocytes d'une multitude d'espèces de mammifères. A ce jour, 33 espèces de Bartonella ont été recensées incluant une vingtaine d'espèces identifiées chez des rongeurs, dont certaines sont associées à des maladies chez l'homme. Des études provenant de différentes parties du monde montrent que les populations de rongeurs hébergent une grande diversité d'espèces de Bartonella avec des taux de prévalence élevés. Plusieurs facteurs liés à l'hôte, au vecteur et à l'environnement dans lequel ils évoluent influencent et auraient, par le passé façonné cette diversité. L'objectif de cette thèse a été d'élucider certains de ces facteurs en étudiant la diversité des souches de Bartonella circulant au sein d'une population de rongeurs sylvatiques dans une zone de forêt périurbaine française, la forêt de Sénart. Dans un premier temps, en nous basant sur une phylogénie précise et robuste, nous avons identifié 63 génotypes apparentés à 3 espèces connues de Bartonella (B. taylorii, B. grahamii et B. doshiae) communément retrouvées au sein des rongeurs sylvatiques en Europe et à une nouvelle espèce proche de B. rochalimae. Nous avons montré que la majorité des souches obtenues lors de cette étude sont fortement associées soit aux campagnols roussâtres soit aux mulots sylvestres. Malgré la barrière physique liée à la spécificité d'hôte, nous avons observé des échanges de matériel génétique entre les souches de Bartonella associées aux campagnols roussâtres et les souches adaptées aux mulots, suggérant que ces souches peuvent cohabiter au sein de leur vecteur. Dans un second temps, en évaluant l'impact de l'espèce bactérienne Borrelia afzelii sur la présence et la diversité des souches de Bartonella au sein d'une population de campagnols roussâtres par des outils statistiques, nous avons observé des co-infections par les deux genres bactériens au sein d'un même rongeur, mais ces deux bactéries ne semble pas interagir