Inhibition of Xanthomonas fragariae, Causative Agent of Angular Leaf Spot of Strawberry, through Iron Deprivation.

In commercial production settings, few options exist to prevent or treat angular leaf spot (ALS) of strawberry, a disease of economic importance and caused by the bacterial pathogen Xanthomonas fragariae. In the process of isolating and identifying X. fragariae bacteria from symptomatic plants, we observed growth inhibition of X. fragariae by bacterial isolates from the same leaf macerates. Identified as species of Pseudomonas and Rhizobium, these isolates were confirmed to suppress growth of X. fragariae in agar overlay plates and in microtiter plate cultures, as did our reference strain Pseudomonas putida KT2440. Screening of a transposon mutant library of KT2440 revealed that disruption of the biosynthetic pathway for the siderophore pyoverdine resulted in complete loss of X. fragariae antagonism, suggesting iron competition as a mode of action. Antagonism could be replicated on plate and in culture by addition of purified pyoverdine or by addition of the chelating agents tannic acid and dipyridyl, while supplementing the medium with iron negated the inhibitory effects of pyoverdine, tannic acid and dipyridyl. When co-inoculated with tannic acid onto strawberry plants, X. fragariae's ability to cause foliar symptoms was greatly reduced, suggesting a possible opportunity for iron-based management of ALS. We discuss our findings in the context of 'nutritional immunity,' the idea that plant hosts restrict pathogen access to iron, either directly, or indirectly through their associated microbiota

\u3cem\u3eiac\u3c/em\u3e Gene Expression in the Indole-3-Acetic Acid-Degrading Soil Bacterium \u3cem\u3eEnterobacter soli\u3c/em\u3e LF7

We show for soil bacterium Enterobacter soli LF7 that the possession of an indole-3-acetic acid catabolic (iac) gene cluster is causatively linked to the ability to utilize the plant hormone indole-3-acetic acid (IAA) as a carbon and energy source. Genome-wide transcriptional profiling by mRNA sequencing revealed that these iac genes, chromosomally arranged as iacHABICDEFG and coding for the transformation of IAA to catechol, were the most highly induced (\u3e29-fold) among the relatively few (iac cluster were genes for a major facilitator superfamily protein (mfs) and enzymes of the β-ketoadipate pathway (pcaIJD-catBCA), which channels catechol into central metabolism. This entire iacHABICDEFG-mfs-pcaIJD-catBCA gene set was constitutively expressed in an iacR deletion mutant, confirming the role of iacR, annotated as coding for a MarR-type regulator and located upstream of iacH, as a repressor of iac gene expression. In E. soli LF7 carrying the DNA region upstream of iacH fused to a promoterless gfp gene, green fluorescence accumulated in response to IAA at concentrations as low as 1.6 μM. The iacH promoter region also responded to chlorinated IAA, but not other aromatics tested, indicating a narrow substrate specificity. In an iacR deletion mutant, gfp expression from the iacH promoter region was constitutive, consistent with the predicted role of iacR as a repressor. A deletion analysis revealed putative −35/−10 promoter sequences upstream of iacH, as well as a possible binding site for the IacR repressor

Ašir

L. Golvin Cité médiévale ruinée dans la région du Titteri (Algérie centrale), à cent cinquante kilomètres à vol d’oiseau au sud d’Alger, sur le flanc méridional du Kef al-Aẖdār al-Šarqī (1464 m d’altitude). Le site, un petit plateau, domine une immense plaine vers le sud. Sa valeur stratégique indéniable en faisait un lieu de prédilection pour l’édification d’une cité forteresse ; véritable sentinelle avancée gardant la montagne contre les entreprises des nomades de la plaine. Au xe siècle, d..

The failed liberalisation of Algeria and the international context: a legacy of stable authoritarianism

The paper attempts to challenge the somewhat marginal role of international factors in the study of transitions to democracy. Theoretical and practical difficulties in proving causal mechanisms between international variables and domestic outcomes can be overcome by defining the international dimension in terms of Western dominance of world politics and by identifying Western actions towards democratising countries. The paper focuses on the case of Algeria, where international factors are key in explaining the initial process of democratisation and its following demise. In particular, the paper argues that direct Western policies, the pressures of the international system and external shocks influence the internal distribution of power and resources, which underpins the different strategies of all domestic actors. The paper concludes that analysis based purely on domestic factors cannot explain the process of democratisation and that international variables must be taken into more serious account and much more detailed

Chenoua

Le massif et sa population (Ph. Leveau) A l’est de la Mitidja, le Chénoua est un petit massif de forme grossièrement ovale mesurant 13 km d’est en ouest, 8 km du nord au sud et baigné au nord par la mer. Un couloir de plateaux et la plaine alluviale de l’oued el-Hachem le séparent des montagnes telliennes du sud. C’est un massif original qui, comme le cap Tenès à l’ouest, appartient à la zone primaire kabyle (zone I de Glangeaud). Une chaîne calcaire formée de lias massif et culminant à 904 m..

Reforming medical education for an integral care with quality

Son innumerables los avances en el desarrollo social y la práctica médica, pudiéndose constatar que muchos de los flagelos de ayer, particularmente aquellos asociados a las condiciones de vida y enfermedades infecciosas, han retrocedido significativamente. Sin embargo, importantes segmentos de nuestra población aun no encuentran una atención integral a sus problemas de salud, lo que además se ve asociado, por ejemplo, a la presencia de nuevos agentes infecciosos, reconfiguraciones demográficas y epidemiológicas, transformaciones sociales y riesgos ambientales que emergen o recrudecen, cambios que no han sido acompañados necesariamente al mismo paso por avances en la educación de los profesionales de la salud en nuestras facultades (1). En varias ocasiones, más allá de discursos y esfuerzos, hemos de reconocer que nuestras aulas han sido testigos de reformas, sin cambios (2) en la esencia o inclusive en la forma con que nuestros estudiantes aprenden.Numerous advances in social development and medical practice can be seen that many of the scourges of yesterday, particularly those associated with living conditions and infectious diseases, have receded significantly. However, important segments of our population still do not find comprehensive attention to their health problems, which is also associated, for example, with the presence of new infectious agents, demographic and epidemiological reconfigurations, social transformations and environmental risks that emerge or they intensify, changes that have not necessarily been accompanied at the same time by advances in the education of health professionals in our faculties (1). On several occasions, beyond speeches and efforts, we must recognize that our classrooms have witnessed reforms, without changes (2) in the essence or even in the way our students learn

Les technologies de l'information et de la communication dans la transition agroécologique

Mobile applications, data and knowledge sharing tools, social networks... digital tools are increasingly present in the agricultural world. This article focuses in particular on the support and relevance of information and communication technologies to support the agro-ecological transition in rural areas.Applications mobiles, outils de partage de données et de connaissances, réseaux sociaux... les outils numériques sont de plus en plus présents dans le monde agricole. Cet article s'intéresse plus particulièrement à l'appui et à la pertinence des technologies de l'information et de la communication pour accompagner la transition agroécologique dans les territoires ruraux

Predictive Ecology and Management of Phyllosphere Microbial Communities Through Cross-Scale Synthesis

In this article, we summarize the main takeaways from a symposium and hybrid virtual and in-person participatory discussion focused on the challenges of scale in understanding the ecology and management of phyllosphere microbial communities. We provide an overview of the confounding effects of spatial scale on inference in microbial ecology, the spatial organization of microbial interactions in the phyllosphere, advances and remaining gaps in measuring phyllosphere colonization across scales, and the epidemiology in the phyllosphere. We hope to motivate further discussion and the development and adoption of creative approaches to solving the challenges of scale to enhance fundamental understanding and practical management of the phyllosphere microbiomes