Molecular architecture of human polycomb repressive complex 2.

Polycomb Repressive Complex 2 (PRC2) is essential for gene silencing, establishing transcriptional repression of specific genes by tri-methylating Lysine 27 of histone H3, a process mediated by cofactors such as AEBP2. In spite of its biological importance, little is known about PRC2 architecture and subunit organization. Here, we present the first three-dimensional electron microscopy structure of the human PRC2 complex bound to its cofactor AEBP2. Using a novel internal protein tagging-method, in combination with isotopic chemical cross-linking and mass spectrometry, we have localized all the PRC2 subunits and their functional domains and generated a detailed map of interactions. The position and stabilization effect of AEBP2 suggests an allosteric role of this cofactor in regulating gene silencing. Regions in PRC2 that interact with modified histone tails are localized near the methyltransferase site, suggesting a molecular mechanism for the chromatin-based regulation of PRC2 activity.DOI:http://dx.doi.org/10.7554/eLife.00005.001

Caenibacterium thermophilum gen. nov., sp. nov., isolated from a thermophilic aerobic digester of municipal sludge

A bacterial strain, N2-680T (=DSM 15264T=LMG 21760T), isolated from a thermophilic aerobic digester of municipal sludge, was characterized with respect to its morphology, physiology and taxonomy. Phenotypically, the isolate was a Gram-negative rod with a polar flagellum, catalase- and oxidase-positive, containing cytoplasmic inclusions of poly-b-hydroxybutyrate and had an optimal growth temperature of about 47 6C. Strain N2-680T was unable to reduce nitrate and could use organic acids, amino acids and carbohydrates as single carbon sources. Chemotaxonomic analysis revealed that ubiquinone 8 was the major respiratory quinone of this organism and that phosphatidylethanolamine and phosphatidylglycerol were the major polar lipids. At 50 6C, the major components in fatty acid methyl ester analysis were C16 : 0 and cyclo-C17 : 0. The highest 16S rDNA sequence identity of isolate N2-680T was to Leptothrix mobilis and Ideonella dechloratans (95?7%) and to Rubrivivax gelatinosus and Aquabacterium commune (95?6 %). 16S rDNA sequence similarities to species of two related thermophilic genera, Caldimonas manganoxidans and Tepidimonas ignava, were lower (93?6 and 94?7 %). On the basis of phylogenetic analyses and physiological and chemotaxonomic characteristics, it is proposed that isolate N2-680T represents a new genus and species, for which the name Caenibacterium thermophilum gen. nov., sp. nov. is propose

Tepidiphilus margaritifer gen. nov., sp. nov., isolated from a thermophilic aerobic digester

A moderately thermophilic bacterium is described, strain N2-214T, that was isolated from an enrichment culture, growing on caprolactone, obtained from a sample from a water-treatment sludge aerobic digester operating at temperatures around 60 °C. The organism was aerobic, Gram-negative, oxidase- and catalase-positive, with a polar flagellum, and capable of growth at temperatures as high as 61 °C. The major fatty acids of strain N2-214T were C16 : 0, C18 : 1 and cyclo-C19 : 0. The phylogenetic relationships of the strain, derived from 16S rRNA gene sequence comparisons, demonstrated it to be a member of the {beta}-subclass of the Proteobacteria. The highest 16S rDNA sequence similarity of isolate N2-214T was to Azoarcus buckelii (91·9 %), Thauera aromatica (92 %) and Hydrogenophilus thermoluteolus (92·7 %). On the basis of phylogenetic analyses and physiological and chemotaxonomic characteristics, it is proposed that isolate N2-214T (=DSM 15129T=LMG 21637T) represents a new genus and species, Tepidiphilus margaritifer gen. nov., sp. nov

Evaluation of the ATB 32C, automicrobic system and API 20C using clinical yeast isolates

The ATB 32C (bioMerieux, Spain), AMS-YBC (Vitek System, bioMerieux, Spain) and API 20C (bioMerieux, Spain) systems were evaluated for their reliability in identifying 100 clinical yeast isolates. The ATB 32C, AMS-YBC and API 20C systems correctly identified 97%, 98% and 100% of the isolates respectively. There were no significant differences in incubation periods between ATB 32C and AMS-YBC systems. One isolate of Candida tropicalis was wrongly identified by the ATB 32C and the AMS-YBC systems. The Saccharomyces cerevisiae isolate was wrongly identified by the ATB 32C system while the AMS-YBC failed to identify it and a third isolate of Candida krusei was wrongly identified by the ATB 32C system. The overall accuracy and rapidity of the ATB 32C and AMS-YBC systems were sufficient to permit recommendation of either of these systems for routine use in the clinical microbiology laboratory, although the first system enjoys the advantages of having a wider data-base and the possibility of manual reading