A new mutation in the pufL gene responsible for the terbutryn resistance phenotype in Rubrivivax gelatinosus

AbstractRubrivivax gelatinosus is a facultative phototrophic non-sulfur bacterium belonging to the β subclass of the purple bacteria. A terbutryn-resistant mutant of R. gelatinosus has been isolated and characterized. Increased resistance levels to terbutryn (300-fold), atrazine (6-fold) and o-phenanthroline (3-fold) were observed for the mutant compared with wild type. Sequence analysis of the mutant revealed a new mutation in the pufL gene coding for the L subunit of the reaction centre (RC) at codon 192 leading to an amino-acid substitution from Gly in the wild type to Asp in the mutant. This substitution is located in the D helix of the L subunit, suggesting an interaction between terbutryn and this part of the polypeptide in the RC of R. gelatinosus. This is the first report of a mutation leading to herbicide resistance and affecting the D helix in purple bacteria. Furthermore R. gelatinosus wild type is highly sensitive to o-phenanthroline compared with other purple bacteria (Rhodobacter capsulatus and Rhodobacter sphaeroides). Sequence comparison of the L subunit from six purple bacteria in which o-phenanthroline sensitivity was measured suggests that SerL226 might be responsible for this phenotype

Fistule cholécysto-biliaire dans le cadre de syndrome de Mirizzi: Cholecysto-biliary fistula in the context of Mirizzi syndrome

Le syndrome de Mirizzi est une étiologie rare de l’ictère rétentionnel suite à une compression de la voie biliaire principale par un calcul enclavé dans le collet vésiculaire ou dans le canal cystique, cette compression peut évoluer vers l’érosion de la paroi du canal hépatique commun et provoquer la formation d’une fistule cholécysto-biliaire. Son diagnostic préopératoire repose sur l’imagerie et surtout la cholangio-IRM, mais la découverte per opératoire de ces dégâts biliaires nécessite une prise en charge chirurgicale appropriée. Nous rapportons le cas d’une patiente de 42 ans, opérait pour un syndrome de Mirizzi et dont l’exploration chirurgicale découvrait une large fistule cholécysto-biliaire traitait par un drainage externe par un drain de kehr et une cholécystectomie antérograde avec suites post opératoires favorables. Mirizzi syndrome is a rare etiology of retentional jaundice caused by a compression of the bile duct by an enclaved stone in the gallbladder neck or in the cystic duct. This compression may progress to erosion of the wall of the common hepatic duct and lead to the formation of a cholecystic-biliary fistula. Its preoperative diagnosis is based on imaging and especially cholangio-MRI, but the peroperative discovery of this biliary damage requires appropriate surgical management. We report the case of a 42-year-old patient, operated for Mirizzi syndrome and whose surgical exploration discovered a large cholecysto-biliary fistula treated by external drainage through a kehr drain and an anterograde cholecystectomy with favourable postoperative follow-up

Thyroïde accessoire ectopique : une observation clinique inhabituelle: Ectopic accessory thyroid gland: an unusual case report

The Ectopic accessory thyroid is a rare embryologic malformation defined as the presence of thyroid tissue outside of its normal position. The coexistence between an accessory thyroid and a thyroid gland in its normal position is exceptional. We report a case of an elderly patient who underwent a surgery for a heteromultinodular goiter with incidental intraoperative discovery of an ectopic accessory thyroid nodule in the anterior mediastinum. L’ectopie thyroïdienne est une malformation embryologique rare qui est une présence de tissu thyroïdien en dehors de sa position normale, la thyroïde accessoire avec une glande thyroïde en place est exceptionnelle. Nous rapportons un cas d’une patiente âgée opérée pour un goitre hétéromultinodulaire avec découverte fortuite per-opératoire d’un nodule thyroïdien accessoire ectopique dans le médiastin antérieur

Biochemical characterization of the carotenoid 1,2-hydratases (CrtC) from Rubrivivax gelatinosus and Thiocapsa roseopersicina

Two carotenoid 1,2-hydratase (CrtC) genes from the photosynthetic bacteria Rubrivivax gelatinosus and Thiocapsa roseopersicina were cloned and expressed in Escherichia coli in an active form and purified by affinity chromatography. The biochemical properties of the recombinant enzymes and their substrate specificities were studied. The purified CrtCs catalyze cofactor independently the conversion of lycopene to 1-HO- and 1,1′-(HO)2-lycopene. The optimal pH and temperature for hydratase activity was 8.0 and 30°C, respectively. The apparent Km and Vmax values obtained for the hydration of lycopene were 24 μM and 0.31 nmol h−1 mg−1 for RgCrtC and 9.5 μM and 0.15 nmol h−1 mg−1 for TrCrtC, respectively. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis revealed two protein bands of 44 and 38 kDa for TrCrtC, which indicate protein processing. Both hydratases are also able to convert the unnatural substrate geranylgeraniol (C20 substrate), which functionally resembles the natural substrate lycopene

Phylogenetic and Evolutionary Patterns in Microbial Carotenoid Biosynthesis Are Revealed by Comparative Genomics

BACKGROUND: Carotenoids are multifunctional, taxonomically widespread and biotechnologically important pigments. Their biosynthesis serves as a model system for understanding the evolution of secondary metabolism. Microbial carotenoid diversity and evolution has hitherto been analyzed primarily from structural and biosynthetic perspectives, with the few phylogenetic analyses of microbial carotenoid biosynthetic proteins using either used limited datasets or lacking methodological rigor. Given the recent accumulation of microbial genome sequences, a reappraisal of microbial carotenoid biosynthetic diversity and evolution from the perspective of comparative genomics is warranted to validate and complement models of microbial carotenoid diversity and evolution based upon structural and biosynthetic data. METHODOLOGY/PRINCIPAL FINDINGS: Comparative genomics were used to identify and analyze in silico microbial carotenoid biosynthetic pathways. Four major phylogenetic lineages of carotenoid biosynthesis are suggested composed of: (i) Proteobacteria; (ii) Firmicutes; (iii) Chlorobi, Cyanobacteria and photosynthetic eukaryotes; and (iv) Archaea, Bacteroidetes and two separate sub-lineages of Actinobacteria. Using this phylogenetic framework, specific evolutionary mechanisms are proposed for carotenoid desaturase CrtI-family enzymes and carotenoid cyclases. Several phylogenetic lineage-specific evolutionary mechanisms are also suggested, including: (i) horizontal gene transfer; (ii) gene acquisition followed by differential gene loss; (iii) co-evolution with other biochemical structures such as proteorhodopsins; and (iv) positive selection. CONCLUSIONS/SIGNIFICANCE: Comparative genomics analyses of microbial carotenoid biosynthetic proteins indicate a much greater taxonomic diversity then that identified based on structural and biosynthetic data, and divides microbial carotenoid biosynthesis into several, well-supported phylogenetic lineages not evident previously. This phylogenetic framework is applicable to understanding the evolution of specific carotenoid biosynthetic proteins or the unique characteristics of carotenoid biosynthetic evolution in a specific phylogenetic lineage. Together, these analyses suggest a "bramble" model for microbial carotenoid biosynthesis whereby later biosynthetic steps exhibit greater evolutionary plasticity and reticulation compared to those closer to the biosynthetic "root". Structural diversification may be constrained ("trimmed") where selection is strong, but less so where selection is weaker. These analyses also highlight likely productive avenues for future research and bioprospecting by identifying both gaps in current knowledge and taxa which may particularly facilitate carotenoid diversification

A paralog of a bacteriochlorophyll biosynthesis enzyme catalyzes the formation of 1,2-dihydro-carotenoids in green sulfur bacteria

Chlorobaculum tepidum, a green sulfur bacterium, utilizes chlorobactene as its major carotenoid, and this organism also accumulates a reduced form of this monocyclic pigment, 1',2'-dihydrochlorobactene. The protein catalyzing this reduction is the last unidentified enzyme in the biosynthetic pathways for all of the green sulfur bacterial pigments used for photosynthesis. The genome of Chlorobaculum tepidum contains two paralogous genes encoding members of the FixC family of flavoproteins: bchP, that has been shown to encode an enzyme of bacteriochlorophyll biosynthesis; and bchO, for which a function has not been assigned. Here we demonstrate that a bchO mutant is unable to synthesize 1',2'-dihydrochlorobactene, and when bchO is heterologously expressed in a neurosporene-producing mutant of the purple bacterium, Rhodobactersphaeroides, the encoded protein is able to catalyze the formation of 1,2-dihydroneurosporene, the major carotenoid of the only other organism reported to synthesize 1,2-dihydrocarotenoids, Blastochloris viridis Identification of this enzyme completes the pathways for the synthesis of photosynthetic pigments in Chlorobiaceae, and accordingly and consistent with its role in carotenoid biosynthesis, we propose to rename the gene, cruI Notably, the absence of cruI in Blastochloris viridis indicates that a second 1,2-carotenoid reductase, which is structurally unrelated to CruI (BchO), must exist in nature. The evolution of this carotenoid reductase in green sulfur bacteria is discussed herein

Apprendre en guerre, apprendre de la guerre : ce que le conflit fait aux territoires de l'école. Le cas des établissements franco-libanais de Beyrouth (1975-1990)

International audienceFor a long time, the poor relation of geography, the school could nevertheless constitute a privileged observatory for analysing the sociospatial recompositions induced by conflict phenomena. We would therefore like to take four steps forward in this paper: Thematically, by betting that the school is a legitimate object for understanding the effect of past and contemporary crises on territories; disciplinary, by placing our methods and concepts at the crossroads of geography, history and sociology; spatially, by focusing our analysis on the Lebanese capital; and temporally, by focusing our reflection on the period from 1975 to 1990, which was marked by a war that was both civil and international. Thus, through the study of four Franco-Lebanese schools in Beirut, teaching students from nursery to the end of secondary school, we will try to show what the war does to the “territories of the school”.Longtemps parent pauvre de la géographie, l'école pourrait pourtant constituer un observatoire privilégié pour analyser les recompositions sociospatiales induites par les phénomènes de conflits. Aussi souhaiterions-nous réaliser pour cette communication quatre pas de côté : thématique, en faisant le pari que l'école est un objet légitime pour rendre intelligible l'effet des crises passées et contemporaines sur les territoires ; disciplinaire, en inscrivant nos méthodes et concepts à la croisée de la géographie, de l'histoire et de la sociologie ; spatial, en arrêtant notre analyse sur la capitale libanaise ; temporel, en faisant porter notre réflexion sur la période courant de 1975 à 1990, marquée par une guerre tout à la fois civile et internationale. Ainsi, à travers l'étude de quatre établissements franco-libanais de Beyrouth, scolarisant des élèves de la maternelle à la terminale, nous chercherons à montrer ce que la guerre fait aux « territoires de l'école »

Phenomene de percolation dans les microemulsions eau/AOT/huile

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