Impact of oleic acid (cis-9-octadecenoic acid) on bacterial viability and biofilm production in Staphylococcus aureus

Staphylococcus aureus is responsible for a broad variety of chronic infections. Most S. aureus clinical isolates show the capacity to adhere to abiotic surfaces and to develop biofilms. Because S. aureus growing in a biofilm is highly refractory to treatment, inhibition of biofilm formation represents a major therapeutic objective. We evaluated the effects of oleic acid on primary adhesion and biofilm production in eight genotypically different S. aureus strains as well as in the biofilm-negative Staphylococcus carnosus strain TM300. Oleic acid inhibited primary adhesion but increased biofilm production in every S. aureus strain tested. Staphylococcus aureus strain UAMS-1 was then selected as a model organism for studying the mechanisms triggered by oleic acid on the formation of a biofilm in vitro. Oleic acid inhibited the primary adhesion of UAMS-1 dose dependently with an IC50 around 0.016%. The adherent bacterial population decreased proportionally with increasing concentrations of oleic acid whereas an opposite effect was observed on the planktonic population. Overall, the total bacterial counts remained stable. Macroscopic detachments and clumps were visible from the adherent bacterial population. In the presence of oleic acid, the expression of sigB, a gene potentially involved in bacterial survival through an effect on fatty acid composition, was not induced. Our results suggest a natural protective effect of oleic acid against primary adhesio

Staphylococcus aureus virulence and metabolism are dramatically affected by Lactococcus lactis in cheese matrix

International audienceIn complex environments such as cheeses, the lack of relevant information on the physiology and virulence expression of pathogenic bacteria and the impact of endogenous microbiota has hindered progress in risk assessment and control. Here, we investigated the behaviour of Staphylococcus aureus, a major foodborne pathogen, in a cheese matrix, either alone or in the presence of Lactococcus lactis, as a dominant species of cheese ecosystems. The dynamics of S. aureus was explored in situ by coupling a microbiological and, for the first time, a transcriptomic approach. Lactococcus lactis affected the carbohydrate and nitrogen metabolisms and the stress response of S. aureus by acidifying, proteolysing and decreasing the redox potential of the cheese matrix. Enterotoxin expression was positively or negatively modulated by both L. lactis and the cheese matrix itself, depending on the enterotoxin type. Among the main enterotoxins involved in staphylococcal food poisoning, sea expression was slightly favoured in the presence of L. lactis, whereas a strong repression of sec4 was observed in cheese matrix, even in the absence of L. lactis, and correlated with a reduced saeRS expression. Remarkably, the agr system was downregulated by the presence of L. lactis, in part because of the decrease in pH. This study highlights the intimate link between environment, metabolism and virulence, as illustrated by the influence of the cheese matrix context, including the presence of L. lactis, on two major virulence regulators, the agr system and saeRS

Daptomycin resistance mechanisms in clinically derived Staphylococcus aureus strains assessed by a combined transcriptomics and proteomics approach

Objectives The development of daptomycin resistance in Staphylococcus aureus is associated with clinical treatment failures. The mechanism(s) of such resistance have not been clearly defined. Methods We studied an isogenic daptomycin-susceptible (DAPS) and daptomycin-resistant (DAPR) S. aureus strain pair (616; 701) from a patient with relapsing endocarditis during daptomycin treatment, using comparative transcriptomic and proteomic techniques. Results Minor differences in the genome content were found between strains by DNA hybridization. Transcriptomic analyses identified a number of genes differentially expressed in important functional categories: cell division; metabolism of bacterial envelopes; and global regulation. Of note, the DAPR isolate exhibited reduced expression of the major cell wall autolysis gene coincident with the up-regulation of genes involved in cell wall teichoic acid production. Using quantitative (q)RT-PCR on the gene cadre putatively involved in cationic peptide resistance, we formulated a putative regulatory network compatible with microarray data sets, mainly implicating bacterial envelopes. Of interest, qRT-PCR of this same gene cadre from two distinct isogenic DAPS/DAPR clinical strain pairs revealed evidence of other strain-dependent networks operative in the DAPR phenotype. Comparative proteomics of 616 versus 701 revealed a differential abundance of proteins in various functional categories, including cell wall-associated targets and biofilm formation proteins. Phenotypically, strains 616 and 701 showed major differences in their ability to develop bacterial biofilms in the presence of the antibacterial lipid, oleic acid. Conclusions Compatible with previous in vitro observations, in vivo-acquired DAPR in S. aureus is a complex, multistep phenomenon involving: (i) strain-dependent phenotypes; (ii) transcriptome adaptation; and (iii) modification of the lipid and protein contents of cellular envelope

BDNF Methylation and Maternal Brain Activity in a Violence-Related Sample

It is known that increased circulating glucocorticoids in the wake of excessive, chronic, repetitive stress increases anxiety and impairs Brain-Derived Neurotrophic Factor (BDNF) signaling. Recent studies of BDNF gene methylation in relation to maternal care have linked high BDNF methylation levels in the blood of adults to lower quality of received maternal care measured via self-report. Yet the specific mechanisms by which these phenomena occur remain to be established. The present study examines the link between methylation of the BDNF gene promoter region and patterns of neural activity that are associated with maternal response to stressful versus non-stressful child stimuli within a sample that includes mothers with interpersonal violence-related PTSD (IPV-PTSD). 46 mothers underwent fMRI. The contrast of neural activity when watching children-including their own-was then correlated to BDNF methylation. Consistent with the existing literature, the present study found that maternal BDNF methylation was associated with higher levels of maternal anxiety and greater childhood exposure to domestic violence. fMRI results showed a positive correlation of BDNF methylation with maternal brain activity in the anterior cingulate (ACC), and ventromedial prefrontal cortex (vmPFC), regions generally credited with a regulatory function toward brain areas that are generating emotions. Furthermore we found a negative correlation of BDNF methylation with the activity of the right hippocampus. Since our stimuli focus on stressful parenting conditions, these data suggest that the correlation between vmPFC/ACC activity and BDNF methylation may be linked to mothers who are at a disadvantage with respect to emotion regulation when facing stressful parenting situations. Overall, this study provides evidence that epigenetic signatures of stress-related genes can be linked to functional brain regions regulating parenting stress, thus advancing our understanding of mothers at risk for stress-related psychopathology

The association of serotonin receptor 3A methylation with maternal violence exposure, neural activity, and child aggression

Background Methylation of the serotonin 3A receptor gene (HTR3A) has been linked to child maltreatment and adult psychopathology. The present study examined whether HTR3A methylation might be associated with mothers' lifetime exposure to interpersonal violence (IPV), IPV-related psychopathology, child disturbance of attachment, and maternal neural activity. Methods Number of maternal lifetime IPV exposures and measures of maternal psychopathology including posttraumatic stress disorder (PTSD), major depression and aggressive behavior (AgB), and a measure of child attachment disturbance known as “secure base distortion” (SBD) were assessed in a sample of 35 mothers and children aged 12–42 months. Brain fMRI activation was assessed in mothers using 30-s silent film excerpts depicting menacing adult male-female interactions versus prosocial and neutral interactions. Group and continuous analyses were performed to test for associations between clinical and fMRI variables with DNA methylation. Results Maternal IPV exposure-frequency was associated with maternal PTSD; and maternal IPV-PTSD was in turn associated with child SBD. Methylation status of several CpG sites in the HTR3A gene was associated with maternal IPV and IPV-PTSD severity, AgB and child SBD, in particular, self-endangering behavior. Methylation status at a specific CpG site (CpG2_III) was associated with decreased medial prefrontal cortical (mPFC) activity in response to film-stimuli of adult male-female interactions evocative of violence as compared to prosocial and neutral interactions. Conclusions Methylation status of the HTR3A gene in mothers is linked to maternal IPV-related psychopathology, trauma-induced brain activation patterns, and child attachment disturbance in the form of SBD during a sensitive period in the development of self-regulation

The GTP-dependant pleiotropic repressor "CodY" regulates biofilm formation in Staphylococcus aureus

Le sujet d'étude de la présente thèse porte sur l'analyse des fonctions du gène appelé /codY /dans la formation de biofilm chez la bactérie /Staphylococcus aureus/. Le gène /codY/ code pour une protéine capable de s'activer en fixant les acides aminés branchés et le GTP. CodY est capable de réprimer l'expression d'une multitude d'autres gènes en se fixant sur des séquences palindromiques présentes dans l'ADN de la bactérie. Les résultats expérimentaux ont montré que i) CodY activé par le GTP réprime la formation de biofilm, ii) CodY se fixe sur /icaB/ et réprime l'expression de /icaADBC/ diminuant ainsi la bio-production de PIA, iii) CodY se fixe aussi dans /icaR/ et réprime l'expression de /icaR/. Finalement, le contrôle transcriptionel complexe de l'opéron /icaADBC/ par CodY implique que cet opéron est régulé en fonction de l'état nutritionnel de la bactérie, lui-même mesuré partiellement par les taux de GTP et d'isoleucine

Epigenomic changes after acupuncture treatment in patients suffering from burnout

Abstract Introduction: The effects of acupuncture treatment in patients suffering from burnout may imply an epigenetic control mediated by DNA methylation changes. In this observational study, a genome-wide characterization of epigenetic changes in blood DNA, before and after acupuncture treatment, was performed in a cohort of 11 patients suffering from burnout. Methods: Burnout was assessed using the Maslach Burnout Inventory (MBI) and DNA was extracted from blood samples and analyzed by Illumina EPIC BeadChip. Results: Before acupuncture, all patients suffered of emotional exhaustion (EE) (MBI-EE score, 44±6), 81% suffered of depersonalization (DP) (MBI-DP score, 16±6), and 72% of low feelings of personal accomplishment (PA) (MBI-PA score, 29±9). After acupuncture, all MBI dimensions improved significantly (EE, 16±11 [p=1.5*10-4]; DP, 4±5 [p=5.3*10-4]; and PA, 40±6 [p=4.1*10-3]). For each patient, both methylomes obtained before and after acupuncture co-clustered in the multidimensional scaling plot, indicating a high level of similarity. Genes corresponding to the 10 most differentially methylated CpGs showed enrichment in the brain dopaminergic signalling, steroid synthesis and in the insulin sensitivity pathways. Conclusion: Acupuncture treatment was found to be highly effective on all burnout dimensions and the epigenetic targets identified were involved in some major disturbances of this syndrome

Intergenerational Transmission of DNA Methylation Signatures Associated with Early Life Stress

Early life stress in humans (i.e. maltreatment, violence exposure, loss of a loved one) and in rodents (i.e. disrupted attachment or nesting, electric shock, restraint, predator odor) occurs during critical steps of neural circuit formation. ELS in humans is associated with increased risk for developmental psychopathology, including anxious and depressive phenotypes. The biological mechanisms underlying these potentially persistent maladaptive changes involve long-term epigenetic modifications, which have been suggested to be potentially transmissible to subsequent generations. DNA methylation is an epigenetic mechanism that modifies gene expression patterns in response to environmental challenges and influences mutation rates. It remains to be seen whether a functionally relevant fraction of DNA methylation marks can escape genome-wide erasures that occur in primordial germ cells and after fertilization within the zygote. Early life-stress-triggered changes in epigenetic mediated transmission of acquired behavioral traits among humans have been assessed mainly by targeting genes involved in the hypothalamic-pituitary-adrenal (HPA) axis, such as NR3C1 and FKBP5. Recently, researchers examining epigenetic transmission have begun to apply genome-wide approaches. In humans, reduced representation bisulfite sequencing (RRBS) was performed on peripheral samples that were obtained from individuals who were prenatally exposed to the “Dutch Hunger Winter”, resulting in two Differentially Methylated Regions (DMRs) in INSR and CPTIA genes that were functionally, biologically and technically validated, and significantly associated with birth weights and LDL cholesterol levels in offspring. In rodents, non-genomic intergenerational transmission of anxiety which was associated with differentially methylated enhancers that were putatively involved in lipid signaling and synaptic/neurotransmission in hippocampal granule cells, was discovered also using RRBS. Finally, transgenerational transmission of altered behaviors was associated with sperm-derived microRNAs produced by ELS male mice. The field of epigenetic transmission is just a beginning to enter the epigenomic era by using genome-wide analyses. Such approaches remain of strong interest to human studies, first in order to help to assess the relevance of the previous targeted studies, and second to discover new important epigenetic modifications of potential clinical importance. New discoveries may help to assess how transmittable the negative impact of stress may be to offspring. The latter may open doors for future treatments and resilience-promoting interventions, as well as new approaches to treat the effects of childhood trauma before the onset of psychiatric disorder

Obtention et perspectives d'un nouvel hybride de caféier en Côte d'Ivoire : l'Arabusta

Après avoir rappelé les buts du programme et les obstacles qu'il a fallu surmonter, l'auteur expose le schéma d'amélioration adopté: création et sélection des géniteurs tétraploïdes C. canephora; collection des géniteurs C. arabica; obtention et étude des hybrides (légitimes, illégitimes, rétrocroisés); contrôle de leur productivité et de leur comportement face aux aléas; méthode de vulgarisation des hybrides. L'A. résume ensuite les expériences entreprises pour mettre au point des pratiques culturales appropriées à l'Arabusta ainsi que sa technologi