887 research outputs found

    Bacteriophage Ď•MAM1, a viunalikevirus, is a broad-host-range, high-efficiency generalized transducer that infects environmental and clinical isolates of the enterobacterial genera Serratia and Kluyvera.

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    Members of the enterobacterial genus Serratia are ecologically widespread, and some strains are opportunistic human pathogens. Bacteriophage Ď•MAM1 was isolated on Serratia plymuthica A153, a biocontrol rhizosphere strain that produces the potently bioactive antifungal and anticancer haterumalide oocydin A. The Ď•MAM1 phage is a generalized transducing phage that infects multiple environmental and clinical isolates of Serratia spp. and a rhizosphere strain of Kluyvera cryocrescens. Electron microscopy allowed classification of Ď•MAM1 in the family Myoviridae. Bacteriophage Ď•MAM1 is virulent, uses capsular polysaccharides as a receptor, and can transduce chromosomal markers at frequencies of up to 7 Ă— 10(-6) transductants per PFU. We also demonstrated transduction of the complete 77-kb oocydin A gene cluster and heterogeneric transduction of a plasmid carrying a type III toxin-antitoxin system. These results support the notion of the potential ecological importance of transducing phages in the acquisition of genes by horizontal gene transfer. Phylogenetic analyses grouped Ď•MAM1 within the ViI-like bacteriophages, and genomic analyses revealed that the major differences between Ď•MAM1 and other ViI-like phages arise in a region encoding the host recognition determinants. Our results predict that the wider genus of ViI-like phages could be efficient transducing phages, and this possibility has obvious implications for the ecology of horizontal gene transfer, bacterial functional genomics, and synthetic biology.This research was supported by the EU Marie-Curie Intra-European Fellowship for Career Development (FP7-PEOPLE-2011-IEF) grant number 298003. The Salmond lab is supported by funding through the Biotechnology and Biological Sciences Research Council (BBSRC, UK). We thank Hazel Aucken and Kornelia Smalla for kindly supplying the environmental and clinical isolates. We would also like to thank Jeremy N. Skepper (Department of Anatomy, University of Cambridge) for assistance in transmission electron microscopy and Alison Rawlinson for technical support.This is the accepted manuscript. The final version is available from the American Society for Microbiology at http://aem.asm.org/content/80/20/6446.lon

    Efficiency at optimal work from finite reservoirs: a probabilistic perspective

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    We revisit the classic thermodynamic problem of maximum work extraction from two arbitrary sized hot and cold reservoirs, modelled as perfect gases. Assuming ignorance about the extent to which the process has advanced, which implies an ignorance about the final temperatures, we quantify the prior information about the process and assign a prior distribution to the unknown temperature(s). This requires that we also take into account the temperature values which are regarded to be unphysical in the standard theory, as they lead to a contradiction with the physical laws. Instead in our formulation, such values appear to be consistent with the given prior information and hence are included in the inference. We derive estimates of the efficiency at optimal work from the expected values of the final temperatures, and show that these values match with the exact expressions in the limit when any one of the reservoirs is very large compared to the other. For other relative sizes of the reservoirs, we suggest a weighting procedure over the estimates from two valid inference procedures, that generalizes the procedure suggested earlier in [J. Phys. A: Math. Theor. {\bf 46}, 365002 (2013)]. Thus a mean estimate for efficiency is obtained which agrees with the optimal performance to a high accuracy.Comment: 14 pages, 6 figure

    The Dynamics of a Strongly Driven Two Component Bose-Einstein Condensate

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    We consider a two component Bose-Einstein condensate in two spatially localized modes of a double well potential, with periodic modulation of the tunnel coupling between the two modes. We treat the driven quantum field using a two mode expansion and define the quantum dynamics in terms of the Floquet Operator for the time periodic Hamiltonian of the system. It has been shown that the corresponding semiclassical mean-field dynamics can exhibit regions of regular and chaotic motion. We show here that the quantum dynamics can exhibit dynamical tunneling between regions of regular motion, centered on fixed points (resonances) of the semiclassical dynamics

    The broad-spectrum antibiotic, zeamine, kills the nematode worm Caenorhabditis elegans.

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    Soil bacteria can be prolific producers of secondary metabolites and other biologically active compounds of economic and clinical importance. These natural products are often synthesized by large multi-enzyme complexes such as polyketide synthases (PKSs) or non-ribosomal peptide synthases (NRPSs). The plant-associated Gram-negative bacterium, Serratia plymuthica A153, produces several secondary metabolites and is capable of killing the nematode worm Caenorhabditis elegans; a commonly used model for the study of bacterial virulence. In this study, we show that disruption of the hybrid PKS/NRPS zeamine (zmn) gene cluster results in the attenuation of "fast-killing" of C. elegans, indicating that zeamine has nematicidal activity. C. elegans also exhibits age-dependent susceptibility to zeamine, with younger worms being most sensitive to the bioactive molecule. The zmn gene cluster is widely distributed within Serratia and phytopathogenic Dickeya species and investigation of strains harboring the zmn gene cluster showed that several of them are highly virulent in C. elegans. Zeamine was described previously as a phytotoxin and broad-spectrum antibacterial compound. In addition to its nematicidal properties, we show here that zeamine can also kill Saccharomyces cerevisiae and Schizosaccharomyces pombe. The expression of the zmn gene cluster and regulation of zeamine production were also investigated. Transcription of the cluster was growth phase-dependent, and was modulated by the post-transcriptional RNA chaperone, Hfq. The results of this study show that zeamine is a highly toxic molecule with little, or no, apparent host specificity in very diverse biological systems. In its current form, zeamine(s) may be useful as a lead compound suitable for chemical modification and structure-activity assays. However, because of widespread non-selective toxicity in multiple bioassays, unmodified zeamine(s) is unlikely to be suitable as a therapeutic antibiotic.MAMV was supported by the EU Marie-Curie Intra-European Fellowship for Career Development (FP7-PEOPLE-2011-IEF), grant number 298003. The Salmond laboratory is supported by funding through the Biotechnology and Biological Sciences Research Council (BBSRC; UK). Work with plant pathogens was carried out under DEFRA licence No. 50864/197900/1.This is the final version of the article. It first appeared at http://dx.doi.org/10.3389/fmicb.2015.0013

    The provenance, date and significance of a Cook-voyage Polynesian sculpture

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    A unique wooden sculpture collected by James Cook during his first voyage to the Pacific is widely considered to be a masterpiece of Oceanic art, but its exact provenance has been unclear. New analysis of shavings from the object now indicate that a) the tree from which it was carved was felled between 1690 and 1728, and that the carving was therefore up to 80 years old when obtained, and b) it originated in Tahiti, despite its stylistic affinities with art from the Austral Islands. Motifs and forms clearly travelled within regions, and populations interacted in ways that blur presumed tribal boundaries. It is perhaps time to reconsider the association between region and style upon which the cataloguing and identification of objects routinely depends.The research reported upon here has taken place in the context of two projects, 'Artefacts of Encounter', funded by the UK Arts and Humanities Research Council over 2010-13, and 'Pacific Presences', funded by the European Research Council over 2013-18. We are grateful to both agencies for their support. We also thank: Julie Adams (British Museum); Peter Brunt (Victoria University); Caroline Cartwright (British Museum); Steven Hooper (University of East Anglia); JeanYves Meyer (Ministère des Ressources Marines, des Mines et de la Recherche, Polynésie Française); Mark Nesbitt (Economic Botany Collection, Royal Botanic Gardens, Kew); Tamsin O’Connell (Dorothy Garrod Laboratory for Isotopic Analysis, McDonald Institute for Archaeological Research); Jessica Royles (Department of Plant Sciences, University of Cambridge); Matthew Spriggs (Australian National University); and the University of Oxford Radiocarbon Accelerator Unit

    Genome Sequence of Serratia plymuthica A153, a Model Rhizobacterium for the Investigation of the Synthesis and Regulation of Haterumalides, Zeamine, and Andrimid.

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    The rhizobacterium Serratia plymuthica A153 is a Gram-negative bacterium belonging to the family Enterobacteriaceae Here, we present the genome sequence of this strain, which produces multiple bioactive secondary metabolites, including the halogenated macrolide oocydin A, the polyamino antibiotic zeamine, and the bacterial acetyl-CoA carboxylase inhibitor andrimid.Work in the Salmond laboratory was supported by the Biotechnology and Biological Sciences Research Council (BBSRC, United Kingdom). Miguel A. Matilla was supported by the EU Marie-Curie intra-European Fellowship For Career Development (FP7-PEOPLE-2011-IEF) grant 298003 and the Spanish Ministry of Economy and Competitiveness Postdoctoral Research Program, Juan de la Cierva (JCI-2012-11815). The Tino Krell laboratory is supported by FEDER funds and Fondo Social Europeo through grants from the Junta de AndalucĂ­a (grant CVI-7335) and the Spanish Ministry for Economy and Competitiveness (grants BIO2013- 42297 and RTC-2014-1777-3).This is the final version of the article. It first appeared from the American Society for Microbiology via http://dx.doi.org/10.1128/genomeA.00373-1

    Tumour inflammatory infiltrate predicts survival following curative resection for node-negative colorectal cancer

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    <b>Background</b>: A pronounced tumour inflammatory infiltrate is known to confer a good outcome in colorectal cancer. Klintrup and colleagues reported a structured assessment of the inflammatory reaction at the invasive margin scoring low grade or high grade. The aim of the present study was to examine the prognostic value of tumour inflammatory infiltrate in node-negative colorectal cancer. <b>Methods</b>: Two hundred patients had undergone surgery for node-negative colorectal cancer between 1997 and 2004. Specimens were scored with Jass’ and Klintrup’s criteria for peritumoural infiltrate. Pathological data were taken from the reports at that time. <b>Results</b>: Low-grade inflammatory infiltrate assessed using Klintrup’s criteria was an independent prognostic factor in node-negative disease. In patients with a low-risk Petersen Index (n = 179), low-grade infiltrate carried a threefold increased risk of cancer death. Low-grade infiltrate was related to increasing T stage and an infiltrating margin. <b>Conclusion</b>: Assessment of inflammatory infiltrate using Klintrup’s criteria provides independent prognostic information on node-negative colorectal cancer. A high-grade local inflammatory response may represent effective host immune responses impeding tumour growth
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