Early diagenesis of carbohydrates and lignin in mangrove sediments subject to variable redox conditions (French Guiana).

A comparative study of lignin and neutral carbohydrate compositions, combined with C, N and δ13C analyses, was carried out on sedimentary cores, and on various vascular plant species collected in mangrove swamps of French Guiana. The main purpose of this study was to assess the diagenesis of carbohydrates and lignin in brackish to hypersaline fine-grained mangrove sediments characterized by great changes in redox conditions. Distribution of carbohydrates in sediments reflects both the lability of these compounds and their efficient recycling. They are subject to selective degradation, cellulosic glucose and xylose appearing to be the two most labile neutral sugars. In contrast a relative increase in arabinose, rhamnose, fucose and hemicellulosic glucose between plants and sediments, suggests that they may be more refractory and/or that they also derive from microbial synthesis. The total carbon from lignin-derived phenols is higher in sediments than in mangrove plants as a consequence of their rather refractory character. Nevertheless, evidence of lignin decomposition was found to be independent of local environmental conditions. The various redox processes that occur in mangrove sediments depend on plant species, stages in forest development and season. Different redox conditions induce different mechanisms for the decomposition of lignin and thus induce changes in phenol distributions. At depth, in most mangroves, an increase in (Ad/Al)v ratios and in deoxy sugars (fucose and rhamnose) content was significantly correlated with increased proportions of oxidized allochthonous organic debris deriving from the Amazonian detrital discharge, thus suggesting a specific source effect rather than a diagenesis induced change. Therefore, this study illustrates that both lignin and cellulose, derived from vascular plant debris, can be degraded in waterlogged mangrove sediments, and that their distribution depends on environmental conditions

The caecal microbiota promotes the acute inflammatory response and the loss of the intestinal barrier integrity during severe Eimeria tenella infection

IntroductionCoccidiosis, a disease caused by intestinal apicomplexan parasites Eimeria, is a threat to poultry production. Eimeria tenella is one of the most pathogenic species, frequently causing a high prevalence of opportunistic infections.ObjectiveThe objective of this study is to investigate the role of the microbiota in the pathogenesis of severe Eimeria tenella infection.MethodsWe have previously shown that microbiota can promote parasite development. To study the effect of the microbiota on the pathogenesis of this infection, we used an experimental condition (inoculum of 10 000 oocysts E. tenella INRAE) in which the parasite load is similar between germ-free and conventional broilers at 7 days post-infection (pi). Thirteen conventional and 24 germ-free chickens were infected. Among this latter group, 12 remained germ-free and 12 received a microbiota from conventional healthy chickens at 4 days pi. Caeca and spleens were collected at 7 days pi.ResultsOur results demonstrated caecal lesions and epithelium damage in conventional chickens at 7 days pi but not in germ-free infected chickens. Administration of conventional microbiota to germ-free chickens partially restored these deleterious effects. At day 7 pi, both infected conventional and germ-free chickens exhibited increased gene expression of inflammatory mediators, including IL15, IFNγ, TNFα and the anti-inflammatory mediator SOCS1, whereas the inflammatory mediators CXCLi2, CCL20, IL18, CSF1, NOS2, PTGS2, IL1β, IL6, the receptor CCR2, and the anti-inflammatory mediators TGFβ1 and IL10 were upregulated only in infected conventional chickens. Notably, the IL18, PTGS2 gene expression was significantly higher in the infected conventional group. Overall, the inflammatory response enhanced by the microbiota might be in part responsible for higher lesion scores. Epithelial tight junction protein gene expression analysis revealed a significant upregulation of CLDN1 with the infection and microbiota, indicating a potential loss of the intestinal barrier integrity.ConclusionThese observations imply that, during E. tenella infection, the caecal microbiota could trigger an acute inflammatory response, resulting in a loss of intestinal integrity. Increase in bacterial translocation can then lead to the likelihood of opportunistic infections. Hence, modulating the microbiota may offer a promising strategy for improving poultry gut health and limiting caecal coccidiosis

Origin and diagenesis of lignin and carbohydrates in mangrove sediments of Guadeloupe (French West Indies): Evidence for a two-step evolution of organic deposits

International audienceThe mangroves of Grande Terre Island (Guadeloupe, French West Indies) are known to store large amounts of organic carbon, and organic-rich sediments have been described to several meters depth. The purpose of the present work was to precisely determine the molecular composition (carbohydrates and lignin-derived phenols) of these organic deposits in relationship with environmental conditions. It was found that within the upper meter of the cores, geochemical data displayed the classical degradation pattern of organic matter (OM) deriving from higher plants. On the one hand, carbohydrates from mangrove tissues underwent fast decomposition, other compounds being simultaneously synthesized by bacteria. On the other hand, lignin phenols were lost rather slowly, i.e. at a similar or lower rate than TOC, their distribution with depth evidencing various lignin decomposition pathways depending on redox conditions. The position of the swamp with respect to salt and fresh water tables strongly influenced these conditions. At depth, results revealed an organic-rich layer, which was characterized by surprisingly well-preserved OM with regard to sugar and phenol compositions. We speculate that the preservation of these compounds might be explained by a rapid and permanent flooding of the mangrove stands that may have occurred more than a thousand years ago. We suggest that the geodynamic context, i.e. the recurrent seismic activity recorded in Guadeloupe, may have induced such a flooding, resulting in the preservation of this OM

Caractérisation de souches d'Escherichia coli pathogènes aviaires de sérogroupe O88

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Origin and Evolution of the Unique Tetra-Domain Hemoglobin from the Hydrothermal Vent Scale Worm Branchipolynoe

Hemoglobin is the most common respiratory pigment in annelids. It can be intra or extracellular, and this latter type can form large multimeric complexes. The hydrothermal vent scale worms Branchipolynoe symmytilida and Branchipolynoe seepensis express an extracellular tetra-domain hemoglobin (Hb) that is unique in annelids. We sequenced the gene for the single-domain and tetra-domain globins in these two species. The single-domain gene codes for a mature protein of 137 amino acids, and the tetra-domain gene codes for a mature protein of 552 amino acids. The single-domain gene has a typical three exon/two intron structure, with introns located at their typical positions (B12.2 and G7.0). This structure is repeated four times in the tetra-domain gene, with no bridge introns or linker sequences between domains. The phylogenetic position of Branchipolynoe globins among known annelid globins revealed that, although extracellular, they cluster within the annelid intracellular globins clade, suggesting that the extracellular state of these Hbs is the result of convergent evolution. The tetra-domain structure likely resulted from two tandem duplications, domain 1 giving rise to domain 2 and after this the two-domain gene duplicated to produce domains 3 and 4. The high O2 affinity of Branchipolynoe extracellular globins may be explained by the two key residues (B10Y and E7Q) in the heme pocket in each of the domains of the single and tetra-domain globins, which have been shown to be essential in the oxygen-avid Hb from the nematode Ascaris suum. This peculiar globin evolutionary path seems to be very different from other annelid extracellular globins and is most likely the product of evolutionary tinkering associated with the strong selective pressure to adapt to chronic hypoxia that characterizes hydrothermal vents

ICEEc2, a New Integrative and Conjugative Element Belonging to the pKLC102/PAGI-2 Family, Identified in Escherichia coli Strain BEN374▿ †

The diversity of the Escherichia coli species is in part due to the large number of mobile genetic elements that are exchanged between strains. We report here the identification of a new integrative and conjugative element (ICE) of the pKLC102/PAGI-2 family located downstream of the tRNA gene pheU in the E. coli strain BEN374. Indeed, this new region, which we called ICEEc2, can be transferred by conjugation from strain BEN374 to the E. coli strain C600. We were also able to transfer this region into a Salmonella enterica serovar Typhimurium strain and into a Yersinia pseudotuberculosis strain. This transfer was then followed by the integration of ICEEc2 into the host chromosome downstream of a phe tRNA gene. Our data indicated that this transfer involved a set of three genes encoding DNA mobility enzymes and a type IV pilus encoded by genes present on ICEEc2. Given the wide distribution of members of this family, these mobile genetic elements are likely to play an important role in the diversification of bacteria

Spread of multidrug-resistant IncHI1 plasmids carrying ESBL gene blaCTX-M-1 and metabolism operon of prebiotic oligosaccharides in commensal Escherichia coli from healthy horses, France

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Compared effect of copper-exchanged zeolite and brown macroalgae <em>Ascophyllum nodosum</em> on fecal excretion of Avian Pathogenic <em>Escherichia coli</em> in a chicken intestinal carriage mode

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Intestinal avian defensin 2 and robustness of chicks

National audiencePoultry production is an important agricultural sector for human food worldwide. Chicks after hatch often face health problems leading to economical losses that are deleterious for breeders. Avian β-defensin 2 (AvBD2) is a prominent host defense peptide of the intestinal mucosa of caecum and is involved in the resistance of poultry to bacterial pathogens. This peptide could thus represent an innate immunity marker of robustness of birds. To test this hypothesis by comparing fast-growing and slow-growing lines in different conditions of breeding, the chick’s caecal AvBD2 content was analysed according to robustness indicators. Chick’s caecal tissue sections labelled by immuno-histo-chemistry with specific antibodies revealed the unexpected localization of AvBD2 in the mucosa with high individual variability, without showing differences attributable to quality indicators, but interestingly showing inverse correlation with plasma IgM levels in the fast-growing line. The availability of our anti-AvBD2 antibodies to the scientific community opens perspectives to identify the cellular sources of this defensin in the caecal mucosa and to investigate the organisation and function of innate immune arsenal of birds

Escherichia coli producteurs de β-lactamases à spectre étendu chez le cheval en France

International audienceObjectif-Introduction : Les animaux de compagnie sont considérés comme un réservoir potentiel de bactéries résistantes aux antibiotiques notamment aux céphalosporines de dernières générations. L’objectif de cette étude était de déterminer le portage intestinal de souches d’Escherichia coli résistantes aux céphalosporines de dernières générations (C3/4G) chez le cheval en France et de caractériser les déterminants génétiques de cette résistance.Matériels et méthodes : Sept-cent-trente-huit chevaux de 41 élevages et centres équestres français ont été échantillonnés pendant l’été 2015. La présence d’E. coli résistants aux céphalosporines de dernières générations a été recherchée dans les crottins. Les gènes de résistance aux C3/4G ont été déterminéss par PCR et séquençage. Les plasmides porteurs de gènes BLSE et/ou céphalosporinase AmpC ont été transférés par conjugaison ou transformation afin d’être caractérisés par typage de réplicon, profil de restriction et multilocus sequence typing. Les souches d’E. coli resistantes aux C3/4G rations ont été caractérisées par champs pulsé, détermination du phylogroupe et du contenu en gènes de virulence.Results: Seize structures équestres hébergeaient au minimum un cheval porteur d’E. coli résistants aux C3/4G, ce qui représentait une prévalence de 7,9% de portage parmi les chevaux échantillonnés. Cinquante-une souches distinctes d’E. coli résistantes aux C3/4G ont été incluses dans l’analyse moléculaire de la résistance. Toutes ces souches présentaient une grande diversité de profil de macrorestriction en champs pulsé XbaI, appartenaient majoritairement au phylogroupe B1 et ne possédaient pas les gènes majeurs de virulence testés pour les animaux suggérant qu’il s’agit de souches commensales non pathogènes. Les BLSE du groupe CTX-M étaient largement prédominante (blaCTX-M-1, n=35; blaCTX-M-2, n=8; blaCTX-M-14, n=2). Les gènes BLSE/AmpC ont été localisés sur différents plasmides appartenant aux groupes d’incompatibilité IncHI1, IncI1, IncN, et IncY. Les gènes BLSE blaCTX-M-1 et blaCTX-M-2 étaient principalement portés par des plasmides IncHI1. Conclusion: Cette étude originale a mis en évidence un portage significatif d’E. coli producteur de BLSE chez le cheval sain en France. Les plasmides porteurs de gènes BLSE sont les acteurs majeurs de la dissémination de la résistance aux C3/4G dans le microbiote intestinal du cheval