Pseudomonas protegens sp. nov., widespread plant-protecting bacteria producing the biocontrol compounds 2,4-diacetylphloroglucinol and pyoluteorin

Fluorescent Pseudomonas strains producing the antimicrobial secondary metabolite 2,4-diacetylphloroglucinol (Phl) play a prominent role in the biocontrol of plant diseases. A subset of Phl-producing fluorescent Pseudomonas strains, which can additionally synthesize the antimicrobial compound pyoluteorin (Plt), appears to cluster separately from other fluorescent Pseudomonas spp. based on 16S rRNA gene analysis and shares at most 98.4% 16S rRNA gene sequence identity with any other Pseudomonas species. In this study, a polyphasic approach based on molecular and phenotypic methods was used to clarify the taxonomy of representative Phl+ Plt+ strains isolated from tobacco, cotton or wheat on different continents. Phl+ Plt+ strains clustered separately from their nearest phylogenetic neighbors (i.e. species from the ‘P. syringae’, ‘P. fluorescens’ and ‘P. chlororaphis’ species complexes) based on rpoB, rpoD or gyrB phylogenies. DNA-DNA hybridization experiments clarified that Phl+ Plt+ strains formed a tight genomospecies that was distinct from P. syringae, P. fluorescens, or P. chlororaphis type strains. Within Phl+ strains, the Phl+ Plt+ strains were differentiated from other biocontrol fluorescent Pseudomonas strains that produced Phl but not Plt, based on phenotypic and molecular data. Discriminative phenotypic characters were also identified by numerical taxonomic analysis and siderotyping. Altogether, this polyphasic approach supported the conclusion that Phl+ Plt+ fluorescent Pseudomonas strains belonged to a novel species for which the name Pseudomonas protegens is proposed, with CHA0T (=CFBP 6595T, =DSM 19095T) as the type strain

Tetrachloromethane-degrading bacterial enrichment cultures and isolates from a contaminated aquifer

The prokaryotic community of a groundwater aquifer exposed to high concentrations of tetrachloromethane (CCl₄) for more than three decades was followed by terminal restriction fragment length polymorphism (T-RFLP) during pump-and-treat remediation at the contamination source. Bacterial enrichments and isolates were obtained under selective anoxic conditions, and degraded 10 mg·L(-1) CCl₄, with less than 10% transient formation of chloroform. Dichloromethane and chloromethane were not detected. Several tetrachloromethane-degrading strains were isolated from these enrichments, including bacteria from the Klebsiella and Clostridium genera closely related to previously described CCl₄ degrading bacteria, and strain TM1, assigned to the genus Pelosinus, for which this property was not yet described. Pelosinus sp. TM1, an oxygen-tolerant, Gram-positive bacterium with strictly anaerobic metabolism, excreted a thermostable metabolite into the culture medium that allowed extracellular CCl₄ transformation. As estimated by T-RFLP, phylotypes of CCl₄-degrading enrichment cultures represented less than 7%, and archaeal and Pelosinus strains less than 0.5% of the total prokaryotic groundwater community

Methylobacterium Genome Sequences: A Reference Blueprint to Investigate Microbial Metabolism of C1 Compounds from Natural and Industrial Sources

Methylotrophy describes the ability of organisms to grow on reduced organic compounds without carbon-carbon bonds. The genomes of two pink-pigmented facultative methylotrophic bacteria of the Alpha-proteobacterial genus Methylobacterium, the reference species Methylobacterium extorquens strain AM1 and the dichloromethane-degrading strain DM4, were compared. Methodology/Principal Findings The 6.88 Mb genome of strain AM1 comprises a 5.51 Mb chromosome, a 1.26 Mb megaplasmid and three plasmids, while the 6.12 Mb genome of strain DM4 features a 5.94 Mb chromosome and two plasmids. The chromosomes are highly syntenic and share a large majority of genes, while plasmids are mostly strain-specific, with the exception of a 130 kb region of the strain AM1 megaplasmid which is syntenic to a chromosomal region of strain DM4. Both genomes contain large sets of insertion elements, many of them strain-specific, suggesting an important potential for genomic plasticity. Most of the genomic determinants associated with methylotrophy are nearly identical, with two exceptions that illustrate the metabolic and genomic versatility of Methylobacterium. A 126 kb dichloromethane utilization (dcm) gene cluster is essential for the ability of strain DM4 to use DCM as the sole carbon and energy source for growth and is unique to strain DM4. The methylamine utilization (mau) gene cluster is only found in strain AM1, indicating that strain DM4 employs an alternative system for growth with methylamine. The dcm and mau clusters represent two of the chromosomal genomic islands (AM1: 28; DM4: 17) that were defined. The mau cluster is flanked by mobile elements, but the dcm cluster disrupts a gene annotated as chelatase and for which we propose the name “island integration determinant” (iid).Conclusion/Significance These two genome sequences provide a platform for intra- and interspecies genomic comparisons in the genus Methylobacterium, and for investigations of the adaptive mechanisms which allow bacterial lineages to acquire methylotrophic lifestyles.Organismic and Evolutionary Biolog

Hydrologie, paludisme et démoustication. (L'exemple de la Région Rhône-Alpes) / Hydrology, malaria and mosquito control : the example of the Rhône-Alpes region, France

Abstract : Hydrology, malaria and mosquito control: the example of the Rhône-Alpes region, France. After analysing historical documents concerning the presence of malaria during the 18th and 19th centuries in the French alpine piedmont (Forez and Dombes wetlands, floodplains of Rhone river and its tributaries), the authors show that the outbreak of the disease in the middle of the last century was a short-term consequence of civil engineering works, the marked increase in mosquito populations resulting from the modification of hydrological parameters associated with the diking of flood- plains. The reasons for the disappearance of malaria around 1883 are discussed and the authors point out that mosquito species capable of transmitting the plasmodium are still present today in the wetlands of the Rhône-Alpes region.Résumé : Après avoir analysé les chroniques se rapportant au paludisme en région Rhône Alpes aux XVIIIe et XIXe siècles, les auteurs montrent que la recrudescence de cette maladie en Savoie, au milieu du siècle dernier, était, en fait, une conséquence (impact à court terme) des travaux de génie civil réalisés dans les plaines alluviales. Les raisons qui auraient entraîné la disparition des « fièvres paludéennes » vers 1883 sont analysées. On montre que les vecteurs transmettant le plasmodium existent encore dans la zone d'étude. L'éventualité de la réapparition de la maladie et la nécessité de limiter les populations de moustiques dans les zones humides du piedmont alpin sont discutées.Pautou Guy, Girel Jacky, Pautou M. P., Gruffaz René. Hydrologie, paludisme et démoustication. (L'exemple de la Région Rhône-Alpes) / Hydrology, malaria and mosquito control : the example of the Rhône-Alpes region, France. In: Revue de géographie alpine, tome 83, n°1, 1995. pp. 33-52

Étude de l’effet pathogène expérimental des spiroplasmes isolés a partir de moustiques sur l’éclosion d’œufs d’

Nous avons soumis des œufs d’Aedes aegypti à l’action de différentes souches de spiroplasmes isolées de moustiques, tant en Savoie française qu’à Taïwan. Seule la souche de spiroplasmes SP7, originaire d’Armigeres subalbatus de Taïwan, témoigne d’un réel effet pathogène sur l’évolution des larves issues des œufs d’Ae. aegypti, sans altération apparente du sex-ratio, ni transmission du pouvoir infectieux aux imagos issues des lots exposés. Les auteurs, après avoir présenté les différents résultats obtenus, évoquent les difficultés, notamment culturales liées à l’emploi des spiroplasmes

Comparative study of 7 fluorescent pseudomonad clinical isolates.

International audienceThere is some debate about the potential survival of Pseudomonas fluorescens at temperatures above 37 degrees C and its consequences for infectious potential, owing to the heterogeneity of clinical strains. Seven clinical strains growing at 37 degrees C or more were submitted for polyphasic identification; 2 were identified as Pseudomonas mosselii and 4 were precisely characterized as P. fluorescens bv. I or II. The binding indexes on glial cells of the strains identified as P. fluorescens bv. I and P. mosselii were compared with that of a reference psychrotrophic strain, P. fluorescens MF37 (bv. V). Clinical P. fluorescens had a similar adherence potential range than strain MF37. Conversely, the binding indexes for P. mosselii strains were 3 times greater than that for strain MF37. These data, and those obtained by comparing the cytotoxic activities of P. fluorescens clinical strains, suggest the existence of different virulence mechanisms, leading either to a low infectious form or to a microorganism with cytotoxic activity in the same range as that of P. mosselii or even Pseudomonas aeruginosa

Hepatitis B virus infection enhances susceptibility towards adeno-associated viral vector transduction <em>in vitro</em> and <em>in vivo</em>.

Gene therapy has become an accepted concept for the treatment of a variety of different diseases. In contrast to pre-clinical models, subjects enrolled in clinical trials including gene therapy possess a history of infection with microbes that may influence its safety and efficacy. Especially viruses that establish chronic infections in the liver, one of the main targets for in vivo gene therapy, raise important concerns. Amongst them is the Hepatitis B virus (HBV), which has chronically infected more than 350 million people worldwide. Here, we investigated the impact of HBV on Adeno-associated viral (AAV) vectors, the most frequently applied gene transfer vehicles for in vivo gene therapy. Unexpectedly we found that HBV greatly improved AAV transduction in cells replicating HBV and identified HBx as a key factor. While HBV-positive and -negative cells were indistinguishable with respect to cell entry efficiency, significantly higher numbers of AAV vector genomes were successfully delivered to the nucleus in the presence of HBV. The HBV-promoting effect was abolished by inhibitors of phosphatidylinositol-3-kinase (PI3K). PI3K was required for efficient trafficking of AAV to the nucleus and was enhanced in HBV-replicating cells and upon HBx expression. Enhancement of AAV transduction was confirmed in vivo using HBV-transgenic mice and could successfully be applied to inhibit HBV progeny release. Conclusion: Our results demonstrate that acute as well as chronic infections with unrelated viruses change the intracellular milieu thereby likely influencing gene therapy outcomes. In case of HBV, the HBx-mediated enhancement of AAV transduction is an advantage that could be exploited for the development of novel treatments of HBV infection