The spin-orbit coupling in the bond formation region of the electronic ground states of O-3(+), S-3(+) and SO2+

International audienceThe potential energy surfaces and the spin-orbit couplings for all states correlating with the lowest dissociation asymptotes (2)Pi + P-3 of the radical cations of ozone, thiozone and sulfur dioxyde have been calculated in the asymptotic and bond forming regions employing full valence CASSCF wavefunctions. For linear geometries, the (2)Pi and (4)Pi states are calculated to be nearly degenerate for distances corresponding to about twice the R, distance of their equilibrium ground state values. Their attractive potentials are distinctly lower than those of the other states. The spin-orbit mixing renders their assignments by spin quantum numbers impossible. This implies that, for instance, the analysis of the observed O-3(+) rotationally resolved spectra near the dissociation threshold must include not only the vibronic couplings between the (X) over tilde (2)A(1) and (A) over tilde B-2(2) states but also very complex angular momentum interactions. Similar behavior is found also for the (2)Pi and (4)Pi states resulting from the lowest asymptote in the S-3(+) and SO2+ radical cations. (c) 2006 Elsevier B.V. All rights reserved

On the formation of S2O at low energies: An ab initio study

International audienceThe potential energy curves and the spin-orbit couplings for all the electronic states correlating with the lowest dissociation asymptote of S2O have been calculated by accurate ab initio approaches, including full-valence complete active space self-consistent field and internally contracted multi-reference configuration interaction. One-dimensional cuts of the three-dimensional potential energy surfaces are presented for linear and bent geometries, providing useful energetic information on the different paths of formation of S2O, starting from various fragments

Phase variation among major surface antigens of Mycoplasma penetrans

International audienceThe pathogenicity and prevalence of Mycoplasma penetrans, a Mycoplasma species recently isolated from humans, are still debated. A major P35 antigen, which is used as target epitope in serological assays, was shown to be a phase-variable lipid-associated membrane protein (LAMP). In this study, we performed a comparative analysis of the LAMP patterns from five M. penetrans clinical isolates and from the type strain. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles and immunoblots with sera serially collected from an M. penetrans-infected patient indicated that these strains expressed different LAMP repertoires. Furthermore, the intraclonal variation in the expression of LAMPs (P34A, P34B, P35, and P38) was monitored by immunoblot analysis with three specific monoclonal antibodies (MAbs) developed in this study and MAb 7 to P35. The phase variation of these LAMPs occurs in an independent manner, with frequencies of variation ranging from 10(-2) to 10(-4) per cell per generation. Consistent with their amphipathic nature, the P34B and P38 antigens were found exposed at the cell surface. The DNA sequence encoding the P38 antigen was defined and found to be related to those of the P35 gene and other putative LAMP-encoding genes, suggesting that these variable antigens are encoded by a family of related genes. Finally, the serum samples from an M. penetrans-infected patient contained antibodies that reacted with a P36 antigen expressed in different M. penetrans strains but not in the isolate recovered from this patient. This result suggested that in vivo phase variation of P36 occurred, which would support a role for these LAMP variations in avoiding the host's immune vigilance

Fermented dairy products modulate Citrobacter rodentium-induced colonic hyperplasia.

We evaluated the protective effects of fermented dairy products (FDPs) in an infection model, using the mouse pathogen Citrobacter rodentium (CR). Treatment of mice with FDP formulas A, B, and C or a control product did not affect CR colonization, organ specificity, or attaching and effacing lesion formation. Fermented dairy product A (FDP-A), but neither the supernatant from FDP-A nor β-irradiated (IR) FDP-A, caused a significant reduction in colonic crypt hyperplasia and CR-associated pathology. Profiling the gut microbiota revealed that IR-FDP-A promoted higher levels of phylotypes belonging to Alcaligenaceae and a decrease in Lachnospiraceae (Ruminococcus) during CR infection. Conversely, FDP-A prevented a decrease in Ruminococcus and increased Turicibacteraceae (Turicibacter). Importantly, loss of Ruminococcus and Turicibacter has been associated with susceptibility to dextran sodium sulfate-induced colitis. Our results demonstrate that viable bacteria in FDP-A reduced CR-induced colonic crypt hyperplasia and prevented the loss of key bacterial genera that may contribute to disease pathology

Safety and functional enrichment of gut microbiome in healthy subjects consuming a multi-strain fermented milk product: a randomised controlled trial

International audienceAbstract Many clinical studies have evaluated the effect of probiotics, but only a few have assessed their dose effects on gut microbiota and host. We conducted a randomized, double-blind, controlled intervention clinical trial to assess the safety (primary endpoint) of and gut microbiota response (secondary endpoint) to the daily ingestion for 4 weeks of two doses (1 or 3 bottles/day) of a fermented milk product (Test) in 96 healthy adults. The Test product is a multi-strain fermented milk product, combining yogurt strains and probiotic candidate strains Lactobacillus paracasei subsp. paracasei CNCM I-1518 and CNCM I-3689 and Lactobacillus rhamnosus CNCM I-3690. We assessed the safety of the Test product on the following parameters: adverse events, vital signs, hematological and metabolic profile, hepatic, kidney or thyroid function, inflammatory markers, bowel habits and digestive symptoms. We explored the longitudinal gut microbiota response to product consumption and dose, by 16S rRNA gene sequencing and functional contribution by shotgun metagenomics. Safety results did not show any significant difference between the Test and Control products whatever the parameters assessed, at the two doses ingested daily over a 4-week-period. Probiotic candidate strains were detected only during consumption period, and at a significantly higher level for the three strains in subjects who consumed 3 products bottles/day. The global structure of the gut microbiota as assessed by alpha and beta-diversity, was not altered by consumption of the product for four weeks. A zero-inflated beta regression model with random effects (ZIBR) identified a few bacterial genera with differential responses to test product consumption dose compared to control. Shotgun metagenomics analysis revealed a functional contribution to the gut microbiome of probiotic candidates

The complete genome sequence of the murine respiratory pathogen Mycoplasma pulmonis

Mycoplasma pulmonis is a wall-less eubacterium belonging to the Mollicutes (trivial name, mycoplasmas) and responsible for murine respiratory diseases. The genome of strain UAB CTIP is composed of a single circular 963 879 bp chromosome with a G + C content of 26.6 mol%, i.e. the lowest reported among bacteria, Ureaplasma urealyticum apart. This genome contains 782 putative coding sequences (CDSs) covering 91.4% of its length and a function could be assigned to 486 CDSs whilst 92 matched the gene sequences of hypothetical proteins, leaving 204 CDSs without significant database match. The genome contains a single set of rRNA genes and only 29 tRNAs genes. The replication origin oriC was localized by sequence analysis and by using the G + C skew method. Sequence polymorphisms within stretches of repeated nucleotides generate phase-variable protein antigens whilst a recombinase gene is likely to catalyse the site-specific DNA inversions in major M.pulmonis surface antigens. Furthermore, a hemolysin, secreted nucleases and a glyco-protease are predicted virulence factors. Surprisingly, several of the genes previously reported to be essential for a self-replicating minimal cell are missing in the M.pulmonis genome although this one is larger than the other mycoplasma genomes fully sequenced until now

Anti-inflammatory Lactobacillus rhamnosus CNCM I-3690 strain protects against oxidative stress and increases lifespan in Caenorhabditis elegans.

Numerous studies have shown that resistance to oxidative stress is crucial to stay healthy and to reduce the adverse effects of aging. Accordingly, nutritional interventions using antioxidant food-grade compounds or food products are currently an interesting option to help improve health and quality of life in the elderly. Live lactic acid bacteria (LAB) administered in food, such as probiotics, may be good antioxidant candidates. Nevertheless, information about LAB-induced oxidative stress protection is scarce. To identify and characterize new potential antioxidant probiotic strains, we have developed a new functional screening method using the nematode Caenorhabditis elegans as host. C. elegans were fed on different LAB strains (78 in total) and nematode viability was assessed after oxidative stress (3 mM and 5 mM H(2)O(2)). One strain, identified as Lactobacillus rhamnosus CNCM I-3690, protected worms by increasing their viability by 30% and, also, increased average worm lifespan by 20%. Moreover, transcriptomic analysis of C. elegans fed with this strain showed that increased lifespan is correlated with differential expression of the DAF-16/insulin-like pathway, which is highly conserved in humans. This strain also had a clear anti-inflammatory profile when co-cultured with HT-29 cells, stimulated by pro-inflammatory cytokines, and co-culture systems with HT-29 cells and DC in the presence of LPS. Finally, this Lactobacillus strain reduced inflammation in a murine model of colitis. This work suggests that C. elegans is a fast, predictive and convenient screening tool to identify new potential antioxidant probiotic strains for subsequent use in humans

Environnement et santé publique: Fondements et pratiques [2e édition]

International audiencePesticides, pollution de l’air, de l’eau et des aliments, changements climatiques, menaces biologiques, chimiques, radiologiques, épidémies et inégalités environnementales de santé… Les sujets d’inquiétude quant aux conséquences de la dégradation de l’environnement sur notre santé sont nombreux et ont besoin d’être compris et analysés à l’aide des connaissances scientifiques actuelles. Unique dans le paysage éditorial et scientifique francophone, cet ouvrage présente les méthodes et approches de la santé publique environnementale d’aujourd’hui. Cette 2e édition s’enrichit de nouvelles perspectives comme la démarche « Une seule santé », le concept d’exposome, et offre une vision globale des impacts sanitaires des changements climatiques. Présentant les grands défis écologiques et les inégalités socio-environnementales de notre temps, plus de 150 auteurs s’appuient sur les données les plus récentes, établissent des objectifs au gré d’exemples illustrés et d’études de cas en Europe, en Afrique et en Amérique du Nord. Alors que les programmes axés sur la santé publique, la santé environnementale, la santé au travail et les sciences de l’environnement connaissent un engouement sans précédent, cet ouvrage est une référence pour les étudiants, enseignants, chercheurs et professionnels de ces disciplines, ainsi que pour les organisations publiques et associatives dans toute la francophonie. (R.A.