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La manipulation des textes est helas un fait trop courant dans la presse pour etre relevee, mais lorsque cette pratique va de pair avec un contresens majeur sur les enjeux d’un projet artistique, il est alors necessaire d’intervenir. Les extraits cites par l’auteur des textes d’introduction ont ete detournes de leur contexte. Quand j’emploie le terme d’aventure, non pour definir l’exposition, mais pour parler de la reconnaissance recente de la creation contemporaine africaine longtemps meconn...

In an attempt to elucidate the origin of the so-called idiopathic spontaneous pneumothorax (ISP), clinical examination, pulmonary function tests, and computed tomography (CT) with visual quantification and density analysis were performed in 20 young patients two months after an ISP episode. Twenty controls were recruited for CT. The chest roentgenograms were normal in the two groups. The results indicated the presence of various types of emphysematous lesions (EL) in the ISP group located predominantly in the apical fields with subpleural location in 16 patients. Interestingly, diffuse but moderate centrilobular emphysema was noted in 12 of 20 patients. The EL visual quantification was always less than 5 percent of the CT slices' total areas. The lung mean density shifted significantly toward the air density in the patient group (patients: -743 +/- 57.5 HU vs controls -713 +/- 59.5 HU, p less than 0.01). These findings suggest that CT may be useful for early assessment of EL in patients with ISP.

Inducible hybrid genes encoding two large domains, a periplasmic domain consisting of the PhoS sequence and an outer membrane domain corresponding to various lengths of the OmpF mature sequence were constructed. The synthetisized hybrid polypeptides are correctly processed during the early times of induction, their precursor forms being accumulated at later times. These hybrids restore sensitivity toward colicin A to ompF E coli B strain which suggests an outer membrane location. At least 2 of them are indeed localized in the outer membrane after immunogold labelling on ultrathin cryosections. Insertation of a hydrophobic sequence between PhoS and OmpF improves the trimerization and the assembly of the OmpF part. Only th hybrids presenting the last C-terminal 29 residues of OmpF are able to promote the colicin N killing action and to exhibit a trimeric conformation which is recognized by specific antibodies. Moreover, the deletion of the C-terminal region impairs the functional insertion of the OmpF domain; this indicates that the last membrane-spanning region of OmpF is necessary for the correct folding and orientation of the protein in the outer membrane.

Various monoclonal antibodies (MoF) directed against cell-surface-exposed epitopes of OmpF, one major outer membrane pore protein of Escherichia coli B and K-12, have been used to study the assembly and the topology of the protein. This paper firstly describes the characterization of the OmpF epitopes recognized by the various monoclonal antibodies. A comparison between OmpC, OmpF, and PhoE porins with respect to their primary amino acid sequence and their cell-surface exposed regions allows us to propose a rough model including 2 antigenic sites. The second part is focused on the assembly of the OmpF protein in the outer membrane. Various forms, precursor, unassembled monomer, metastable oligomer (pre-trimer) and trimer are detected with immunological probes directed against OmpF during a kinetic analysis of the process. The requirement for a concomitant lipid synthesis during the trimerization has been demonstrated by investigating the presence of a specific native epitope. The role of lipopolysaccharide during the stabilization of the conformation is discussed with regard to the various steps of assembly.

Root absorption selectivity, which refers to the fact that the mineral elements are not found in the same proportions in the plant as in the growth medium, was characterized using plots where the proportions between the elements were considered. Grain sorghum was grown hydroponically in nutrient solutions where the cationic macroelements were increasingly replaced with sodium and the anionic macronutrients with chloride. The data obtained from the analyses of the nutrient solutions and of the whole plants show that root selectivity promotes the absorption of K+ and NO3 ‐ ‐N and impedes that of Ca++ whereas there is nearly no selectivity towards the other nutrients (Mg, P, S).The high negative selectivity towards unessential elements (Na and Cl) is reflected by their very low proportions within the plant. The comparison between the various plant organs shows that the proportions of the essential elements are nearly identical in the roots, the sheaths, the younger leaves and in the adult leaves (on...

Many regulatory rules related to home-based care for cancer patients issued during the recent years. More precisely, the French Plan cancer and the December 2004arrêtéaim atfacilitating home-based chemotherapy by injectiononlywithin the framework of a network of health in oncology, this in order to improve the quality of care and quality of life of patients. In this context, the Onco Pays-de-la-Loire network launched a project with centralised preparations of chemotherapy administred at home. We describe in this study the first results of this experiment. 41 patients have been treated and 224 cytotoxic drugs sended since january 2007 (56 % with trastuzumab, 19 % with gemcitabin, 13 % with methotrexate and 12 % with fluorouracil). No major problem was detected, 1,9 % of the preparations were destroyed. Satisfaction of outpatient healthcare professionals was good. A comparison of estimated costs revealed reductions in costs for outpatient chemotherapy. These first results validate the interest of cancer treatment at home for this kind of patients, and show the importance of nurse and pharmaceutical coordination.

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Shigella surface protein IcsA and its cytoplasmic derivatives are localized to the old pole of rod-shaped cells when expressed in Escherichia coli. In spherical mreB cells, IcsA is targeted to ectopic sites and close to one extremity of actin-like MamK filament. To gain insight into the properties of the sites containing polar material, we studied the IcsA localization in spherical cells. GFP was exported into the periplasm via the Tat pathway and used as a periplasmic space marker. GFP displayed zonal fluorescence in both mreB and rodA-pbpA spherical E. coli cells, indicating an uneven periplasmic space. Deconvolution images revealed that the cytoplasmic IcsA fused to mCherry was localized outside or at the edge of the GFP zones. These observations strongly suggest that polar material is restricted to the positions where the periplasm possesses particular structural or biochemical properties.

Texte de la communication orale présentée lors de la Journée AESA-AEEMA, 19 mai 2006; National audience; The RESPE, network for the epidemio-surveillance in equine pathology, has been monitoring equine influenza in France since 1999. This surveillance not only allows the estimation of viral circulation intensity and horse pathology, but is also a good means of collecting circulating strains and checking the good appropriateness of vaccine and circulating strains. The distribution of equine populations monitored by the RESPE has been estimated from a survey of sentinel veterinarians achieved in 2006. This survey has shown that the cover of the network is heterogenous, both geographically and regarding the kind of equine population, since some areas have no sentinel veterinarians and since only 3% of carthorses and donkeys are covered by the RESPE whereas almost 2/3 race horses and breeding horses are monitored. Moreover, the results of these six years of existence are based on 182 confirmed equine influenza cases and 96 outbreaks (including one or more cases). The existence of national census for some populations has allowed to estimate the coverage rate of the network and the incidence of influenza per horse category. Finally, phylogenetic studies based on strains isolated or amplified in France have shown that strains from both European and American lineages have circulated as in the rest of the world. A unique genotype of the American lineage (sublineage Florida) has circulated in 13/14 outbreaks reported in 2005/2006. Even though the RESPE does not offer a maximal coverage of the equine population yet, the incidence estimations have shown that race horses are far more concerned by these infections than the other populations (riding schools and all other populations). The horse races category is at the same time the most monitored population.; Le RESPE, Réseau d'Epidémio-Surveillance en Pathologie Equine, effectue une surveillance de la grippe équine en France depuis 1999. Cette surveillance permet non seulement d'estimer l'intensité de la circulation virale et de la pathologie chez le cheval en France, mais aussi de collecter les souches circulantes et vérifier la bonne adéquation des souches vaccinales avec ces souches. Une enquête effectuée en 2006 sur la clientèle des vétérinaires sentinelles impliqués dans ce réseau a permis d'estimer la population équine surveillée dans le cadre du RESPE. Elle a montré que la couverture est hétérogène, à la fois sur le plan géographique et selon le type d'équidés, puisque certaines zones géographiques ne comptent aucun vétérinaire sentinelle et que seulement 3% des chevaux de trait et ânes sont couverts par le réseau contre plus de 60% des chevaux de course et d'élevage pur sang. En outre, le bilan des six années d'existence du RESPE se fonde sur 182 cas de grippe équine confirmés ainsi que 96 foyers (comprenant un ou plusieurs cas). L'existence de données nationales de recensement pour certaines populations équines a permis d'obtenir une estimation de l'indice de couverture du réseau et de l'incidence des foyers de grippe selon les catégories d'équidés. Enfin, les études de phylogénie sur des souches isolées ou amplifiées en France ont montré que des souches des deux lignages européen et américain ont circulé ces dernières années, de même que dans le reste du monde et qu'un même génotype du lignage américain (sous-lignage Floride) a circulé dans 13 foyers français sur 14 en 2005/2006. Même si ce réseau n'offre pas encore une couverture exhaustive de la population équine française, les estimations de l'incidence de la grippe équine ont permis de constater que l'incidence est nettement plus importante dans les populations de chevaux de course que dans celle des centres équestres ou dans les autres catégories d'équidés. Les populations les plus à risque sont donc également les mieux surveillées par le RESPE.

International audience

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The scorpion hepatopancreas consists of digestive diverticula and interstitial tissue. A digestive diverticulum is composed of two differentiated cell types: the secretory zymogene-like cells and the digestive cells which are the most abundant. The scorpion digestive lipase (SDL) has been previously purified from scorpion hepatopancreas, but its cellular localization has not yet been established. Polyclonal antibodies specific to SDL were prepared and used in immunofluorescence and immunogold techniques to determine the cellular location of SDL. Our results clearly established that SDL was detected intracellularly in specific vesicles tentatively named (SDL+) granules of the digestive cells. No immunolabelling was observed in secretory zymogene-like cells. This immunocytolocalization indicates that lipid digestion might occur in specific granules inside the digestive cells, as suggested by previous studies on the scorpion digestive process.

The marine Roseobacter clade comprises one of the largest fractions of heterotrophic marine bacteria and accounts for about 16% of 16S rRNA gene clones retrieved from marine bacterioplankton. Their global distribution seems to be related to oceanic water masses and their environmental and biogeochemical properties. In this study, we report isolation and characterization of novel Roseobacter clade members from the Yellow Sea, China. Phylogenetic analysis of 16S rRNA gene sequences reveals that the new isolates (YSCB1, YSCB2, YSCB3 and YSCB4) are closely related to uncultured Arctic seawater bacterium R7967 (99.57-100% sequence identity) and to the cultured Roseobacter sp. DSS-1 (99.27-99.76% sequence identity) isolated from the southeastern coastal water of the USA. Interestingly, YSCB strains possess unique intracellular chromium-containing aggregates. Therefore, these novel Roseobacter clade members exhibit a peculiar property in mineral biogeneration. (c) 2006 Elsevier SAS. All rights reserved.

The ubiquity and importance of photosynthetic organisms in nature has made the molecular mechanisms of photosynthesis a widely studied subject at both structural and functional levels. A current challenge is to understand the supramolecular assembly of the proteins involved in photosynthesis in native membranes. We have used atomic force microscopy to study the architecture of the photosynthetic apparatus and analyze the structure of single molecules in chromatophores of Phaeospirillum molischianum. Core complexes are formed by the reaction center enclosed by an elliptical light harvesting complex 1. LH2 are octameric rings, assembled either with cores or in hexagonally packed LH2 antenna domains. The symmetry mismatch caused by octameric LH2 packing in a hexagonal lattice, that could be avoided in a square lattice, suggests lipophobic effects rather than specific inter-molecular interactions drive protein organization. The core and LH2 complexes are organized to form a supramolecular assembly reminiscent to that found in Rhodospirillum photometricum, and very different from that observed in Rhodobacter sphaeroides, Rb. blasticus, and Blastochloris viridis.

When antidoping control detects a prohibited substance in specimens collected of a horse at the end of a race, the consequences are serious both for the horse and for its trainer. It is therefore in everyone’s interest to collect the samples in strict compliance with the rules of good practice. The general conditions of sample collection, packaging and shipping are specified., Dans le cadre du contrôle antidopage, lorsqu’une substance prohibée est mise en évidence dans les prélèvements d’un cheval contrôlé à l’issue d’une course, les conséquences sont importantes, tant pour le cheval que pour son entraîneur. Il convient donc, dans l’intérêt de tous, que le prélèvement soit effectué avec la plus grande rigueur, selon des règles de bonne pratique. Les dispositions générales qui régissent sa réalisation, les modalités d’exécution, de conditionnement et d’envoi sont précisées., Bernadac Michel. Les prélèvements en Courses : premier maillon, mais maillon essentiel. In: Bulletin de l'Académie Vétérinaire de France tome 158 n°1, 2005. pp. 51-55.

We present a multi-user W-CDMA baseband channel unit processor ASIC for cellular base station applications. The ASIC is compliant with the 3GPP/UMTS standard and exceeds 3GPP minimum requirements for high-speed data by 2.1 to 6.35 dB. It supports up to 8 users simultaneously, with a mix of voice and data services and a maximum uplink data rate of 384 kbps. The ASIC implements preamble detection, searching, RAKE-finger demodulation, channel coding/decoding for voice and data services, and transmission functions. It is coupled to a DSP to form a complete channel element for 8 users. The ASIC has 1.88 M gates plus 2.7 Mbits of SRAM in a 0.16 /spl mu/m CMOS process at 61.44 MHz.

"The Encyclopedia of applied plant sciences covers the application of current advances in the biological sciences, through which scientists can now better produce sustainable, safe food, feed and food ingredients, and renewable raw materials for industry and society. This three-volume set also covers the concerns over continuing advances in the application of knowledge in the areas of ecology and plant pathology, genetics, physiology, biochemistry and biotechnology, as well as the ethical issues involved in the use of the powerful techniques available to modern plant science."

Outer membrane vesicle formation occurs during Gram-negative bacterial growth. However, natural production of large amounts of outer membrane vesicles has only been described in a few bacterial genera. The purified vesicles of some bacterial pathogens have shown potential applications in vaccinology and in antibiotic therapy. This study focused on the development of a gene expression system able to induce production of large amounts of outer membrane vesicles. The Tol-Pal system of Escherichia coli, required to maintain outer membrane integrity, is composed of five cell envelope proteins, TolA, TolB, TolQ, TolR and Pal. Tol proteins are parasitized by filamentous bacteriophages and by colicins. The phage infection process and colicin import require, respectively, the N-terminal domain of the minor coat g3p protein and the translocation domain of colicins, with both domains interacting with Tol proteins. In this study, we show that the periplasmic production of either Tol, g3p or colicin domains was able to specifically destabilize the E. coli or Shigella flexneri cell envelope and to induce production of high amounts of vesicles. This technique was further found to work efficiently in Salmonella enterica serovar Typhimurium.

The mitotic cyclin Clb2 plays a major role in promoting M-phase in budding yeast, despite its functional redundancy with three closely related cyclins Clb1, Clb3 and Clb4. Here, we further investigate the mechanisms controlling the cellular distribution of Clb2 in living cells. In agreement with observations recently made by Hood et al. [Hood, J. K., Hwang, W. W. and Silver, P. A. (2001) J. Cell Sci. 114, 589-597], we find that GFP-tagged Clb2 expressed from its natural promoter localizes to various cellular compartments, including the nucleus, the mitotic spindle, the spindle pole bodies as well as the mother-bud neck. The neck localization is specific to Clb2 as Clb1, Clb3 and Clb4 are never observed there, even when over-expressed. Mutational analysis identifies a central region of Clb2, comprising residues 213-255 and a phylogenetically conserved hydrophobic patch, as an essential cis-acting determinant. Clb2 co-localizes with the bud site selection protein Bud3. Consistent with a role of Bud3 in targeting Clb2 to the bud neck, we report a two-hybrid interaction between these proteins. Furthermore, Clb2 is shown to be specifically delocalized in Δbud3 cells and in a bud3 mutant deleted for its C-terminal Clb2-interacting domain (bud3Δ1221), but not in a Δbud10 mutant. Correlating with this phenotype, bud3Δ1221 cells exhibit a pronounced (15-30 minutes) delay in cytokinesis and/or cell separation, suggesting an unanticipated function of Clb2 in these late mitotic events. Taken together, our data uncover a new role for Bud3 in cytokinesis that correlates with its capacity to target Clb2 at the neck, independently of its well established cell-type-specific function in bud site selection.

Moussu Claire, Saison Anne, Bermann Frédéric, Pitel Pierre-Hugues, Bernadac Michel, Zientara Stéphan. La myoglobinurie atypique des équidés : une nouvelle maladie ?. In: Bulletin de l'Académie Vétérinaire de France tome 156 n°1, 2003. pp. 72-74.

Communication présentée lors des Journées AEEMA-AESA, 22-23 mai 2003; National audience; In autumn 2002 (between 17 October and 31 November), 66 grazing horses (located in 34 french area) suffered a prostrating illness caused by a myopathy and died (56/66) within 12 to 72h. They were suspected to developed atypical myoglobinuria according to clinical and epidemiological investigations and were registrated by the French national Network for epidemiological surveillance of Equine Diseases (RESPE). Althought several outbreaks were described in other european countries (England, Germany, Ireland, Switzerland, Denmark, Lettony), it was the first description in France. Serum biochemical abnormalities (elevated muscle and hepatic enzymes) and myoglobinury were demonstrated. The affected horses were mainly young and permanent grazing horses. A number of potential aetiological and contributory factors (vegetal poisoning, mycotoxins, bacterial toxins?) were considered, but the aetiology remains unresolved.; A l'automne 2002 (entre le 17 Octobre et le 31 Novembre), le RESPE recensait 66 chevaux (répartis dans 34 foyers) atteints de myopathie, décédant, pour la plupart, en 12 à 72h et présentant un tableau clinique et épidémiologique compatibles avec le syndrome « myoglobinurie atypique ». Ce syndrome, décrit depuis 1986 dans plusieurs pays européens (Angleterre, Allemagne, Belgique, Irlande, Suisse, Danemark, Lettonie), était resté jusqu'à ce jour inconnu en France. Il est associé à des modifications hémato-biochimiques (augmentation des enzymes musculaires et hépatiques) et à une myoglobinurie. La Belgique (Wallonie) a enregistré à la même période, une quarantaine de cas suspects. Les chevaux atteints en France étaient principalement de jeunes chevaux à l'herbage. L'enquête épidémiologique et les examens complémentaires ont rapidement été orientés vers l'hypothèse d'une intoxination (bactéries ou mycotoxines) ou d'une intoxication en relation avec l'environnement proche des animaux, mais l'étiologie reste encore à ce jour inconnue.

Charentais melons (Cucumis melo L., var cantalupensis Naud.) in which ethylene biosynthesis has been suppressed by an antisense ACC oxidase gene have been used to better understand the role of ethylene in the regulation of the ripening process of climacteric fruit and on the development of sensory qualities. We have shown that a number of biochemical and molecular processes associated with the ripening of climacteric fruit are ethylene-independent. In some cases, such as softening of the flesh, the same pathway comprises both ethylene-dependent and -independent components. The various ethylene-dependent events exhibit differential sensitivity to ethylene. The threshold level for degreening of the rind is 1 ppm, while 2.5 ppm are required to trigger the ethylene-dependent component of the softening process. The saturating level of ethylene for all these events is less than 5 ppm, which is by far lower than the internal ethylene concentrations found in the fruit at the climacteric peak (around 100 ppm). Detachment of the fruit influences the development of respiratory climacteric. Fruit remaining attached to the vine, although producing higher levels of ethylene, exhibit a reduced climacteric rise in respiration as compared to detached fruit. The response of antisense ACO fruit to exogenous ethylene in terms of respiration is higher in detached than in attached fruit. Ethylene-suppressed melons show a severe reduction of aroma volatiles production, particularly in ester production. In the biosynthetic pathway of aliphatic esters, the dehydrogenation of fatty acids and aldehydes appears to be ethylene-dependent. In contrast, alcohol acetylation comprises ethylene-dependent and ethylene-independent components, probably corresponding to differentially regulated alcohol acetyl transferases. In terms of sensory quality, these data show that the extension of shelf-life through the inhibition of ethylene production has some beneficial effects on texture and sugar accumulation but is detrimental for the generation of aroma.

The Tol-Pal system of gram-negative bacteria is composed of five proteins. TolA, TolQ, and TolR are inner membrane proteins, TolB is a periplasmic protein, and Pal, the peptidoglycan-associated lipoprotein, is anchored to the outer membrane. In this study, the roles of Pal and major lipoprotein Lpp were compared in Escherichia coli. lpp and tol-pal mutations have previously been found to perturb the outer membrane permeability barrier and to cause the release of periplasmic proteins and the formation of outer membrane vesicles. In this study, we showed that the overproduction of Pal is able to restore the outer membrane integrity of an lpp strain but that overproduced Lpp has no effect in a pal strain. Together with the previously reported observation that overproduced TolA complements an lpp but not a pal strain, these results indicate that the cell envelope integrity is efficiently stabilized by an epistatic Tol-Pal system linking inner and outer membranes. The density of Pal was measured and found to be lower than that of Lpp. However, Pal was present in larger amounts compared to TolA and TolR proteins. The oligomeric state of Pal was determined and a new interaction between Pal and Lpp was demonstrated.

Objectif ameliorer la prise en charge des patients hospitalises chez les quels une hyperglycemie est decouverte fortuitement. Patients et methodes observation initiale : sur 12 jours consecutifs, etude de la prise en charge des patients ayant une glycemie > 2 g/l observee pour la premiere fois au laboratoire de l’hopital. 83 patients consecutifs depistes moyenne d’âge : 72,2 (29–99), dont 65 ont moins de 80 ans. Glycemie moyenne : 2,81 g/l (2,01–8,90), 32 diabetes connus, 51 decouvertes. Sur les decouvertes 35 (69 %) n’ont pas ete pris en consideration, 4 (8 %) ont beneficie d’un avis specialise et d’une annonce. Une campagne d’information par email et par information directe dans les services a ete realisee sur la conduite a tenir : controle hba1c, acetone et glycemie a jeun, suivi d’avis specialise si hba1c > 6,5 % Resultats 4 mois apres meme technique de prelevement population : 89 patients Age moyen : 68,5 (30–93), 67 ont moins de 80 ans. Diabete connu 49 (55 %), decouverte d’une hyperglycemie 40 (45 %), 19 ont eu plusieurs mesures glycemiques : (47,5 %), 8 ont eu hba1c Conclusion La prevalence des patients hyperglycemiques a l’hopital est importante. La meconnaissance d’un diabete augmente le risque d’infection severe et la mortalite. Beaucoup de travail d’information reste a faire. Le nombre de glycemies excessives non pris en compte est important (2/3 des hyperglycemies presentes). Un avis specialise a ete sollicite 1 fois sur 2 quand le diabete est connu mais seulement dans 10 % des decouvertes d’hyperglycemies

The outer membrane of gram-negative bacteria acts as a barrier against harmful lipophilic compounds and larger molecules unable to diffuse freely through the porins. However, outer membrane proteins together with the Tol-Pal and TonB systems have been exploited for the entry of macromolecules such as bacteriocins and phage DNA through the Escherichia coli cell envelope. The TonB system is involved in the active transport of iron siderophores and vitamin B12, while no more precise physiological role of the Tol-Pal system has yet been defined than its requirement for cell envelope integrity. These two systems, containing an energized inner membrane protein interacting with outer membrane proteins, share similarities.

The contradiction between airborne transmission of Puumala virus and the low rate of airway manifestations reported in hemorrhagic fever with renal syndrome (HFRS) caused by this virus led us to conduct this study to check whether the incidence of respiratory manifestations may have been underestimated.We retrospectively reviewed 129 consecutive cases of HFRS diagnosed between 1983 and 1995 in the eastern France.Clinical manifestations of airway involvement and chest X-ray abnormalities were observed in 30% and 50% of the patients respectively. Analysing the radiological anomalies by serum creatinine level showed that in two-thirds of the cases (33% of all the HFRS cases) they were concomitant with acute renal failure and probably related to pulmonary edema, and that in one-third (17% of the HFRS cases) they were compatible with pneumonia. These cases of pneumonia could correspond to specific manifestations of the hantavirus Puumala at the site of penetration.Although minimally expressive, respiratory manifestations were found to be more frequent than expected in hemorrhagic fever with renal syndrome. Incidence may have been formerly underestimated.

Various sulfate-reducing bacteria of the genera Desulfovibrio and Desulfomicrobium were tested and compared for enzymatic reduction of chromate. Our study demonstrated that the ability to reduce chromate is widespread among sulfate-reducing bacteria. Among them, Desulfomicrobium norvegicum reduced Cr(VI) with the highest reaction rate. This strain grew in the presence of up to 500 μM chromate, but Cr(VI) reduction in the absence of sulfate was not associated with growth. The presence of chromate induced morphological changes and leakage of periplasmic proteins into the medium. The ability of isolated polyheme cytochromes c from sulfate- and sulfur-reducing bacteria to reduce chromate was also analyzed. Tetraheme cytochrome c3(Mr. 13,000) from Desulfomicrobium norvegicum showed twice as much activity as either tetraheme cytochrome c3 from Desulfovibrio vulgaris strain Hildenborough or triheme cytochrome c7 from Desulfuromonas acetoxidans. Results with cytochromes c3 and other c-type cytochromes altered by site-directed mutagenesis indicated that negative redox potential hemes are crucial for metal reductase activity. The present study also demonstrated that the (Fe) hydrogenase from sulfate-reducing bacteria could reduce chromate.

The bacterial twin arginine translocation (Tat) pathway is capable of exporting cofactor-containing enzymes into the periplasm. To assess the capacity of the Tat pathway to export heterologous proteins and to gain information about the property of the periplasm, we fused the twin arginine signal peptide of the trimethylamine N-oxide reductase to the jellyfish green fluorescent protein (GFP). Unlike the Sec pathway, the Tat system successfully exported correctly folded GFP into the periplasm of Escherichia coli. Interestingly, GFP appeared as a halo in most cells and occasionally showed a polar localization in wild type strains. When subjected to a mild osmotic up-shock, GFP relocalized very quickly at the two poles of the cells. The conversion from the halo structure to a periplasmic gathering at particular locations was also observed with spherical cells of the DeltarodA-pbpA mutant or of the wild type strain treated with lysozyme. Therefore, the periplasm is not a uniform compartment and the polarization of GFP is unlikely to be caused by simple invagination of the cytoplasmic membrane at the poles. Moreover, the polar gathering of GFP is reversible; the reversion was accelerated by glucose and inhibited by azide and carbonyl cyanide m-chlorophenylhydrazone, indicating an active adaptation of the bacteria to the osmolarity in the medium. These results strongly suggest a relocalization of periplasmic substances in response to environmental changes. The polar area might be the preferential zone where bacteria sense the change in the environment.

In order to gain more information on the molecular basis by which ethylene regulates the ripening process, we used the differential display approach to isolate early ethylene-responsive (ER) genes from late immature-green tomato fruit. Among the isolated ER clones many correspond to regulatory genes involved either in signal transduction or in transcriptional and post-transcriptional regulation. ER43 and ER50 share significant homology with a GTP-binding protein and a Raf kinase from the CTR1 type, respectively. ER24 is homologous to the multibridging factor MBF1, a component of the TAF complex (TATA box binding protein associated factor). Finally, ER49, a putative mitochondrial translational elongation factor is potentially involved in the ethylene postranscriptional regulation of gene expression.

Mutations in the tol-pal genes induce pleiotropic effects such as release of periplasmic proteins into the extracellular medium and hypersensitivity to drugs and detergents. Other outer membrane defective strains such as tolC , lpp , and rfa mutations are also altered in their outer membrane permeability. In this study, electron microscopy and Western blot analyses were used to show that strains with mutations in each of the tol-pal genes formed outer membrane vesicles after growth in standard liquid or solid media. This phenotype was not observed in tolC and rfaD cells in the same conditions. A tolA deletion in three different Escherichia coli strains was shown to lead to elevated amounts of vesicles. These results, together with plasmid complementation experiments, indicated that the formation of vesicles resulted from the defect of any of the Tol-Pal proteins. The vesicles contained outer membrane trimeric porins correctly exposed at the cell surface. Pal outer membrane lipoprotein was also immunodetected in the vesicle fraction of tol strains. The results are discussed in view of the role of the Tol-Pal transenvelope proteins in maintaining outer membrane integrity by contributing to target or integrate newly synthesized components of this structure.

National audience