PEPTIDES EXTRACTED FROM ARTEMISIA HERBA ALBA HAVE ANTIMICROBIAL ACTIVITY AGAINST FOODBORNE PATHOGENIC GRAM-POSITIVE BACTERIA

Background: Artemisia herba alba, classified into the family of Asteraceae, is an aromatic herb that is traditionally used as a purgative and anti-pyretic folk medicine by rural people of south Tunisia. This study reports the first identification of antimicrobial peptides from this medicinal plant that inhibited the growth of several food-borne pathogenic bacteria. Materials and methods: The extraction and purification of peptidic agents from Artemisia herba alba, have been performed using precipitation by ammonium sulfate of a phosphate buffer crude extract obtained from the plant leaves, followed by reverse-phase HPLC on a C18 column. The mass of the peptides was estimated by SDS-PAGE electrophoresis, followed by a gel overlay assay and ultra-filtration through a 5 kDa cut-off membrane. Fractions from every purification steps were sampled and assayed for activity towards different food-borne bacterial strains pathogenic and non pathogenic to humans. Results: The phosphate buffer crude extract, as well as its ammonium sulfate precipitate, designated AS-P, inhibited the growth of Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus sensu stricto and the new approved species Bacillus cytotoxicus. AS-P MICs (minimum inhibitory concentrations) ranged from 0.241 to 3.8 mg/ml proteins for L. monocytogenes and B. cereus sensu stricto (strains ATCC10987 and IP5832), respectively. The bioactive AS-P molecules were stable up to 10 minutes heating at 120°C and they resisted organic solvent effects. Antimicrobial activity of A. herba alba AS-P decreased to 40 and 60% after proteolytic treatment with trypsin and proteinase K, respectively, suggesting peptides being responsible for the A. herba alba AS-P activity. The mass of antibacterial A. herba alba peptides was estimated below 5 kDa. Two AS-P fractions, eluted at 40 and 37% acetonitrile, showed antibacterial activity when assayed against L. monocytogenes. Conclusion: A. herba alba could make a new source of novel natural anti-infective agents that could be used in food bio-preservation as natural additives or in human infectious disease treatments against multi-drug resistant pathogens

The implications of carbon dioxide and methane exchange for the heavy mitigation RCP2.6 scenario under two metrics

Greenhouse gas emissions associated with Representative Concentration Pathway RCP2.6 could limit global warming to around or below a 2 °C increase since pre-industrial times. However this scenario implies very large and rapid reductions in both carbon dioxide (CO2) and non-CO2 emissions, and suggests a need to understand available flexibility between how different greenhouse gases might be abated. There is a growing interest in developing a greater understanding of the particular role of shorter lived non-CO2 gases as abatement options. We address this here through a sensitivity study of different methane (CH4) emissions pathways to year 2100 and beyond, by including exchanges with CO2 emissions, and with a focus on related climate and economic advantages and disadvantages. Metrics exist that characterise gas equivalence in terms of climate change effect per tonne emitted. We analyse the implications of CO2 and CH4 emission exchanges under two commonly considered metrics: the 100-yr Global Warming Potential (GWP-100) and Global Temperature Potential (GTP-100). This is whilst keeping CO2-equivalent emissions pathways fixed, based on the standard set of emissions usually associated with RCP2.6. An idealised situation of anthropogenic CH4 emissions being reduced to zero across a period of two decades and with the implementation of such cuts starting almost immediately gives lower warming than for standard RCP2.6 emissions during the 21st and 22nd Century. This is despite exchanging for higher CO2 emissions. Introducing Marginal Abatement Cost (MAC) curves provides an economic assessment of alternative gas reduction strategies. Whilst simpler than utilising full Integrated Assessment Models (IAMs), MAC curves are more transparent for illustrative modelling. The GWP-100 metric places a relatively high value on climate change prevented for methane emission reduction, as compared to an equivalent mass of CO2 reduction. This in combination with the strong non-linearity in MAC curves (moving quickly from relatively cheap removal to emissions difficult to cut at any cost) causes little change under cost minimisation from standard RCP2.6 emissions. This reflects the original development of RCP2.6 standard emissions from similar minimisation. With gas exchange under GTP-100, however, we find much less methane is abated, resulting in higher temperatures, whilst costs are slightly lower. Our results also highlight the point at which greater methane mitigation would become beneficial from both a climate and economic aspect. If by 2030 removal of all methane were to become possible at an average cost less than $1000 per tonne of CH4, then this would be the cheapest option, for GWP-100 metric and our CO2 MAC curve. Critically this would increase the possibility of constraining warming to two degrees

Lost-time illness, injury and disability and its relationship with obesity in the workplace: A comprehensive literature review

The objective of this study was to conduct a literature review examining predictors of lost-time injury, illness and disability (IID) in the workplace, with a focus on obesity as a predictor, and to evaluate the relationship between obesity and losttime IID. The study objective was also to analyze workplace disability prevention and interventions aimed at encouraging a healthy lifestyle among employees and reducing obesity and IID, as well as to identify research gaps. The search was conducted in several major online databases. Articles included in the review were published in English in peer-reviewed journals between January 2003 and December 2014, and were found to be of good quality and of relevance to the topic. Each article was critically reviewed for inclusion in this study. Studies that focused on lost-time IID in the workplace were reviewed and summarized. Workers in overweight and obese categories are shown to be at a higher risk of workplace IID, are more likely to suffer from lost-time IID, and experience a slower recovery compared to workers with a healthy body mass index (BMI) score. Lost-time IID is costly to an employer and an employee; therefore, weight reduction may financially benefit both – workers and companies. It was found that some companies have focused on developing interventions that aid reduction of weight and the practice of active lifestyle among their employees. Int J Occup Med Environ Health 2016;29(5):749–76

Necrotrophism Is a Quorum-Sensing-Regulated Lifestyle in Bacillus thuringiensis

How pathogenic bacteria infect and kill their host is currently widely investigated. In comparison, the fate of pathogens after the death of their host receives less attention. We studied Bacillus thuringiensis (Bt) infection of an insect host, and show that NprR, a quorum sensor, is active after death of the insect and allows Bt to survive in the cadavers as vegetative cells. Transcriptomic analysis revealed that NprR regulates at least 41 genes, including many encoding degradative enzymes or proteins involved in the synthesis of a nonribosomal peptide named kurstakin. These degradative enzymes are essential in vitro to degrade several substrates and are specifically expressed after host death suggesting that Bt has an active necrotrophic lifestyle in the cadaver. We show that kurstakin is essential for Bt survival during necrotrophic development. It is required for swarming mobility and biofilm formation, presumably through a pore forming activity. A nprR deficient mutant does not develop necrotrophically and does not sporulate efficiently in the cadaver. We report that necrotrophism is a highly regulated mechanism essential for the Bt infectious cycle, contributing to spore spreading

The PlcR Virulence Regulon of Bacillus cereus

PlcR is a Bacillus cereus transcriptional regulator, which activates gene expression by binding to a nucleotidic sequence called the ‘PlcR box’. To build a list of all genes included in the PlcR regulon, a consensus sequence was identified by directed mutagenesis. The reference strain ATCC14579 sequenced genome was searched for occurrences of this consensus sequence to produce a virtual regulon. PlcR control of these genes was confirmed by comparing gene expression in the reference strain and its isogenic Δ-plcR strain using DNA microarrays, lacZ fusions and proteomics methods. The resulting list included 45 genes controlled by 28 PlcR boxes. Forty of the PlcR controlled proteins were exported, of which 22 were secreted in the extracellular medium and 18 were bound or attached to cell wall structures (membrane or peptidoglycan layer). The functions of these proteins were related to food supply (phospholipases, proteases, toxins), cell protection (bacteriocins, toxins, transporters, cell wall biogenesis) and environment-sensing (two-component sensors, chemotaxis proteins, GGDEF family regulators). Four genes coded for cytoplasmic regulators. The PlcR regulon appears to integrate a large range of environmental signals, including food deprivation and self cell-density, and regulate the transcription of genes designed to overcome obstacles that hinder B. cereus growth within the host: food supply, host barriers, host immune defenses, and competition with other bacterial species. PlcR appears to be a key component in the efficient adaptation of B. cereus to its host environment

IlsA, A Unique Surface Protein of Bacillus cereus Required for Iron Acquisition from Heme, Hemoglobin and Ferritin

The human opportunistic pathogen Bacillus cereus belongs to the B. cereus group that includes bacteria with a broad host spectrum. The ability of these bacteria to colonize diverse hosts is reliant on the presence of adaptation factors. Previously, an IVET strategy led to the identification of a novel B. cereus protein (IlsA, Iron-regulated leucine rich surface protein), which is specifically expressed in the insect host or under iron restrictive conditions in vitro. Here, we show that IlsA is localized on the surface of B. cereus and hence has the potential to interact with host proteins. We report that B. cereus uses hemoglobin, heme and ferritin, but not transferrin and lactoferrin. In addition, affinity tests revealed that IlsA interacts with both hemoglobin and ferritin. Furthermore, IlsA directly binds heme probably through the NEAT domain. Inactivation of ilsA drastically decreases the ability of B. cereus to grow in the presence of hemoglobin, heme and ferritin, indicating that IlsA is essential for iron acquisition from these iron sources. In addition, the ilsA mutant displays a reduction in growth and virulence in an insect model. Hence, our results indicate that IlsA is a key factor within a new iron acquisition system, playing an important role in the general virulence strategy adapted by B. cereus to colonize susceptible hosts

Approche chronobiologique du controle de la vitellogenese chez le Crustace isopode Porcellio dilatatus Brandt

SIGLECNRS T 56597 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Agglomération : étude expérimentale et simulation numérique réalisée sur un système liquide-solide pulvèrulent

L'étude du processus d’agglomération est menée dans le cas d'un système liquide-solide divisé au voisinage de l'équilibre thermodynamique (saturation). On constate que la vitesse d'agglomération est une fonction linéaire du nombre de particules en solution. Un modèle est alors proposé où le processus d'agglomération est attribué aux collisions particules élémentaires-agglomérats. On détermine expérimentalement la conductivité du milieu et ses propriétés de transmission et diffraction de la lumière, ce qui permet ainsi d'obtenir les paramètres relatifs à la phase liquide et solide. Finalement, une simulation numérique du processus permet de comparer les résultats expérimentaux et la modélisation théorique

Etude expérimentale et théorique des processus déterminant l'évolution des systèmes solide-liquide avec ou sans création de phase

Les opérations industrielles de cristallisation adoptent en général une démarche phénoménologique qui consiste à choisir en fonction de la qualité recherchée du produit les valeurs des paramètres d'action sans réellement maîtriser, à l'échelle élémentaire, l'ensemble des processus à l'origine de la cristallogenèse. Une des conséquences de cette démarche est un surcoût de production qu'une maîtrise ou du moins une meilleure connaissance des mécanismes de la cristallisation pourrait partiellement éviter. A l échelle du laboratoire, l étude fondamentale de la précipitation doit nécessairement concerner un système simple où l'ensemble des caractéristiques des phases liquide et solide peuvent être aisément déterminées. Celui-ci doit d'autre part, permettre l étude des processus concourant à la formation de la phase solide. Les travaux exposés ont pour but de déterminer l'influence de certains paramètres d'action et/ou d'effectuer une modélisation numérique, cinétique ou thermodynamique des étapes unitaires de la cristallisation. Celles-ci sont présentées à travers ce mémoire indépendamment les unes des autres ce qui permet au lecteur de se référer à un processus déterminé sans avoir acquis la connaissance des autres parties de cette thèse. Les parties bibliographiques sont importantes. En effet, les études de synthèse concernant les mécanismes de la cristallisation sont rares ou inexistantes dans la littérature de langue française. Les processus, dont ce travail fait état ont été déterminés dans des conditions thermodynamiques différentes en raison de la nécessité de les étudier indépendamment les uns des autres lorsque cela fût possible. Le schéma suivant expose leur classement par rapport au paramètre fondamental, constitué par la concentration de la solution au sein de laquelle la phase solide pulvérulente évolue.ST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF