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ABSTRACT Pseudomonas spp. colonize diverse aquatic and terrestrial habitats and produce a wide variety of secondary metabolites, including lipopeptides. However, previous studies have often examined a limited number of lipopeptide-producing strains. In this study, we performed a systematic analysis of lipopeptide production across a wide data set of strains of the Pseudomonas syringae complex (724) by using a combined bioinformatics, mass spectrometry, and phylogenetics approach. The large P. syringae complex, which is composed of 13 phylogroups, is known to produce factins (including syringafactin-like lipopeptides), mycins (including syringomycin-like lipopeptides), and peptins (such as syringopeptins). We found that 80.8% of P. syringae strains produced lipopeptides and that factins were the most frequently produced (by 96% of the producing strains). P. syringae strains were either factin monoproducers or factin, mycin, and peptin coproducers or lipopeptide nonproducers in relation to their phylogenetic group. Our analyses led to the discovery of 42 new lipopeptides, bringing the number of lipopeptides identified in the P. syringae complex to 75. We also highlighted that factins have high structural resemblance and are widely distributed among the P. syringae complex, while mycins and peptins are highly structurally diverse and patchily distributed. IMPORTANCE This study provides an insight into the P. syringae metabolome that emphasizes the high diversity of lipopeptides produced within the P. syringae complex. The production profiles of strains are closely related to their phylogenetic classification, indicating that structural diversification of lipopeptides parallels the phylogeny of this bacterial complex, thereby further illustrating the inherent importance of lipopeptides in the ecology of this group of bacteria throughout its evolutionary history. Furthermore, this overview of P. syringae lipopeptides led us to propose a refined classification that could be extended to the lipopeptides produced by other bacterial groups.

Rhamnolipids (RLs) and fengycins (FGs) are amphiphilic lipid compounds from bacteria secretomes proposed to replace synthetic pesticides for crop protection. They both display plant defense triggering properties and direct antimicrobial activities. In particular, they have well reported antifungal effects against phytopathogenic fungi. RLs and FGs are considered to act through a direct interaction with membrane lipids and a destabilization of microorganism plasma membrane, thereby limiting the risk of resistance emergence. The main objective of this work was to gain insights in the antimycelial mode of action of these metabolites to promote them as environment and human health friendly biocontrol solutions. Their biocidal effects were studied on two Sclerotiniaceae fungi responsible for diseases in numerous plant species worldwide. We show here that different strains of Botrytis cinerea and Sclerotinia sclerotiorum have opposite sensitivities to RLs and FGs on plate experiments. Overall, B. cinerea is more sensitive to FGs while S. sclerotiorum is more sensitive to RLs. Electron microscopy observations demonstrated that RLs induce mycelial destructuring by asperities emergence and hyphal fusions whereas FGs promote swelling and formation of vesicle-like structures due to vacuole fusions and autophagy. Permeability studies, phosphatidylserine externalization and reactive oxygen species production assessments showed a programmed cell death triggering by RLs at medium concentrations (until 50 μg mL−1) and necrosis characteristics at higher concentration. Programmed cell death was always observed on hyphae treated with FGs. Quantifications of mycelial ergosterol content indicated that a higher ergosterol rate in S. sclerotiorum correlates with increasing sensitivity to RLs. Oppositely, a lower ergosterol rate in B. cinerea correlates with increasing sensitivity to FGs, which was confirmed by ergosterol biosynthesis inhibition with tebuconazole. This gain of knowledge will help to better understand the mode of action of RLs and FGs to fight specific plant fungal diseases.

Dès les années 90 le sociologue britannique Basil Bernstein reprochait aux travaux de Bourdieu et aux théories de la Reproduction (mais la question vaut d’être également posée à bien d’autres sociologies de l’éducation qui se posent en alternative à ces théories) de demeurer trop générales, de ne pas se soucier suffisamment de l’analyse interne des structures et modes de fonctionnement du champ éducatif, et de ne pouvoir ainsi « fournir des principes puissants de description des instances pédagogiques, de leurs discours, de leurs pratiques » (Bernstein, 2007, p. 26). De fait, à de rares exceptions près, la fonction de transmission du savoir et ses modalités pratiques apparaissent comme le parent pauvre de la sociologie de l'éducation : objet opaque et objet suspect, « mauvais objet », mystification, leurre derrière lesquels se cacheraient les « véritables fonctions » (reproduction sociale, aliénation, domestication...) de l'institution scolaire dont la sociologie aurait pour objet de rechercher et dévoiler les modes opératoires. Cette réticence est devenue un obstacle pour décrire et analyser, et donc pour contribuer à transformer, les processus concrets par lesquels se produisent, entre contextes et situations, les inégalités scolaires, de classe et de genre. Il nous faut au contraire pour cela savoir nouer des rapports renouvelés entre sociologie, psychologie culturelle et didactique. Nous montrerons, à partir d’exemples tirés d’observations prolongées de classes ordinaires, combien la théorie de Bernstein constitue un outil précieux pour construire un cadre conceptuel et des méthodologies empiriques au service de cet objectif.

Septoria tritici blotch, caused by the fungal pathogen Zymoseptoria tritici, is a highly significant disease on wheat crops worldwide. The objective of the present study was to find out new bacterial strains with bio-antimicrobial activity against Z. tritici. Two phyllospheric bacteria (S1 and S6) were isolated from wheat ears and identified as Bacillus velezensis strains according to 16S rRNA Sanger sequencing. Antagonistic assays performed with either living strains or cell-free culture filtrates showed significant in vitro antifungal activities against Z. tritici. For the culture filtrates, the half-maximal inhibitory dilution and the minimal inhibitory dilution were 1.4% and 3.7% for the strain S1, and 7.4% and 15% for the strain S6, respectively. MALDI—ToF analysis revealed that both strains synthesize cyclic lipopeptides but from different families. Interestingly, only strain S1 produces putative bacillomycin D. Such differential lipopeptide production patterns might explain the difference observed between the antifungal activity of the culture filtrates of the two strains. This study allows the identification of new lipopeptide-producing strains of B. velezensis with a high potential of application for the biocontrol of Z. tritici.

Aims Biocontrol products based on microorganisms and natural substances are promising alternatives to chemical pesticides that could contribute to develop a more sustainable agriculture. Here, we investigated the potential of cell-free culture filtrates (CFCFs) from two strains of the Bacillus subtilis group to inhibit Zymoseptoria tritici , a major fungal pathogen of wheat. Methods and results Foliar application of CFCFs from Bacillus velezensis GA1 and Bacillus sp. III1 on wheat seedlings in a greenhouse strongly reduced Z. tritici disease severity (>90%). In vitro bioassays showed that CFCFs completely inhibited the spore germination and fungal growth (100%). In planta cytological investigations revealed a significant impact of the treatments on both spore germination (∼40% inhibition) and fungal growth of Z. tritici (>80% inhibition). High Performance Liquid Chromatography (HPLC) analysis showed that the Bacillus strains displayed different lipopeptide profiles. The CFCF obtained from Bacillus GA1 contained 90 mg l−1 of iturin A + surfactins + fengycins and the CFCF obtained from Bacillus sp. III1 contained 25 mg l−1 of mojavensin A (iturin family) + surfactins + fengycins. Conclusions Strains of the B. subtilis group producing different iturins could provide several CFCF-based solutions for the biocontrol of Z. tritici. [ABSTRACT FROM AUTHOR]

Abstract Background Tuberculosis (TB) is caused by Mycobacterium tuberculosis and represents one of the major challenges facing drug discovery initiatives worldwide. The considerable rise in bacterial drug resistance in recent years has led to the need of new drugs and drug regimens. Model systems are regularly used to speed-up the drug discovery process and circumvent biosafety issues associated with manipulating M. tuberculosis. These include the use of strains such as Mycobacterium smegmatis and Mycobacterium marinum that can be handled in biosafety level 2 facilities, making high-throughput screening feasible. However, each of these model species have their own limitations. Results We report and describe the first complete genome sequence of Mycobacterium aurum ATCC23366, an environmental mycobacterium that can also grow in the gut of humans and animals as part of the microbiota. This species shows a comparable resistance profile to that of M. tuberculosis for several anti-TB drugs. The aims of this study were to (i) determine the drug resistance profile of a recently proposed model species, Mycobacterium aurum, strain ATCC23366, for anti-TB drug discovery as well as Mycobacterium smegmatis and Mycobacterium marinum (ii) sequence and annotate the complete genome sequence of this species obtained using Pacific Bioscience technology (iii) perform comparative genomics analyses of the various surrogate strains with M. tuberculosis (iv) discuss how the choice of the surrogate model used for drug screening can affect the drug discovery process. Conclusions We describe the complete genome sequence of M. aurum, a surrogate model for anti-tuberculosis drug discovery. Most of the genes already reported to be associated with drug resistance are shared between all the surrogate strains and M. tuberculosis. We consider that M. aurum might be used in high-throughput screening for tuberculosis drug discovery. We also highly recommend the use of different model species during the drug discovery screening process.

Les notions d’échec scolaire et de démocratisation du système éducatif et de l’accès au(x) savoir(x) sont à la fois étroitement liées et éminemment problématiques. Polysémiques, elles désignent des réalités contradictoirs, que l’analyse se doit évidemment de distinguer mais perd beaucoup à opposer. Mieux comprendre, pour mieux agir, requiert dès lors de travailler à dépasser le risque d’un partage du travail entre une sociologie des inégalités scolaires insuffisamment soucieuse des modalités effectives des activités de transmission et d’appropriation des savoirs et techniques intellectuelles, et une recherche en pédagogie et en psychologie des apprentissages insuffisamment soucieuse des différents contextes sociaux, institutionnels et didactiques dans lesquels ces activités sont toujours situées. Ce qui nous demande de savoir établir des rapports renouvelés entre sociologie, psychologie et didactique.

Nos últimos 20 anos, a noção de relação com o saber difundiu-se e foi usada amplamente, tanto na esfera da pesquisa em educação quanto nas da formação de docentes e de profissionais do sistema educacional ou do debate social relativo à escola. O êxito teórico e institucional, e até mesmo mediático, do sintagma relação com o saber indica, creio eu, convergências reais que, no entanto, não devem minimizar as questões e os debates teóricos e sociais por ele suscitados. Refletindo sobre os debates suscitados pelo uso, em perspectivas e quadros teóricos distintos, por diferentes pesquisadores e coletivos de pesquisa, de noções semelhantes (de relação com o saber, mas também de experiência escolar, por exemplo), o objetivo deste artigo é tentar esclarecer os desafios teóricos, empíricos e sociais desses debates e neles haurir novos recursos para pensar e agir.During the last 20 years, the notion of relation to knowledge has become disseminated, and it has been widely employed in the fields of education research, education of teachers and other professionals in the education system, and in the social debate about school. This theoretical and institutional - and even mediatic - success of the relation to knowledge syntagm signals, in my view, to real convergences that, however, should not diminish the importance of the theoretical or social questions and debates this notion elicits. Reflecting on the debates raised by the use by various researchers and research groups of similar notions (of relation to knowledge, but also of school experience, for instance) under different perspectives and theoretical frameworks, the objective of this paper is to clarify the theoretical, empirical and social challenges entailed by these debates, and extract from them new resources to think and act.