697 research outputs found
Variation in siderophore biosynthetic gene distribution and production across environmental and faecal populations of Escherichia coli.
No full textIron is essential for Escherichia coli growth and survival in the host and the external environment, but its availability is generally low due to the poor solubility of its ferric form in aqueous environments and the presence of iron-withholding proteins in the host. Most E. coli can increase access to iron by excreting siderophores such as enterobactin, which have a very strong affinity for Fe3+. A smaller proportion of isolates can generate up to 3 additional siderophores linked with pathogenesis; aerobactin, salmochelin, and yersiniabactin. However, non-pathogenic E. coli are also able to synthesise these virulence-associated siderophores. This raises questions about their role in the ecology of E. coli, beyond virulence, and whether specific siderophores might be linked with persistence in the external environment. Under the assumption that selection favours phenotypes that confer a fitness advantage, we compared siderophore production and gene distribution in E. coli isolated either from agricultural plants or the faeces of healthy mammals. This population-level comparison has revealed that under iron limiting growth conditions plant-associated isolates produced lower amounts of siderophores than faecal isolates. Additionally, multiplex PCR showed that environmental isolates were less likely to contain loci associated with aerobactin and yersiniabactin synthesis. Although aerobactin was linked with strong siderophore excretion, a significant difference in production was still observed between plant and faecal isolates when the analysis was restricted to strains only able to synthesise enterobactin. This finding suggests that the regulatory response to iron limitation may be an important trait associated with adaptation to the non-host environment. Our findings are consistent with the hypothesis that the ability to produce multiple siderophores facilitates E. coli gut colonisation and plays an important role in E. coli commensalism
Richardson, Barbauld, and the construction of an early modern fan club
No full textMPhilMuch has been written about the life and long works of the eighteenth century epistolary novelist, Samuel Richardson, but the prospect of his position as the first celebrity novelist – responsible for courting his own fame as well as initiating his own fan club – has largely been ignored. The body of manuscripts housed at the National Art Library in the Victoria and Albert Museum in London provides the modern scholar with evidence of the skeletal beginnings of an early fan club. This thesis aims to show how these manuscripts were turned into a saleable commodity by the publisher and entrepreneur Richard Phillips, while under the guiding hand of another, slightly later, literary celebrity, Anna Laetitia Barbauld. In order to restore Richardson’s reputation amongst a new nineteenth century audience, Barbauld was required to construct her own idea of him as an eighteenth century celebrity author, and in doing so the insecurities of a self-professed, apparently diffident man, are revealed. Barbauld’s capacious, but heavily edited selection of letters is analyzed in this thesis, providing ample evidence that Richardson’s correspondents were more than just eager letter writers. By using Barbauld’s biography of Richardson this thesis aims to show how she manipulates the genre of life writing in her construction of him.
This thesis offers an alternative reading of how the Richardson manuscripts are viewed, redefining them as not simply a collection of letters, but as a collective entity, deliberately selected and archived as evidence of an early modern fan club, and its celebrity managing director
Detection of secondary predation by PCR analyses of the gut contents of invertebrate generalist predators
No full textPredation by generalist predators is difficult to study in the field because of the complex effects of positive and negative interactions within and between predator species and guilds. Predation can be monitored by molecular means, through identification of prey DNA within predators. However, polymerase chain reaction (PCR) amplification of prey DNA from predators cannot discriminate between primary and secondary predation (hyperpredation), in which one predator feeds on another that has recently eaten the target prey. Here we quantify, for the first time, the potential error caused by detection of prey DNA following secondary predation, using an aphid–spider–carabid model. First, the aphid Sitobion avenae was fed to the spider Tenuiphantes tenuis and the carabid Pterostichus melanarius, and the postconsumption detection periods, for prey DNA within predators, were calculated. Aphids were then fed to spiders and the spiders to carabids. Aphid DNA was detected in the predators using primers that amplified 245- and 110-bp fragments of the mitochondrial cytochrome oxidase I gene. Fragment size and predator sex had no significant effect on detection periods. Secondary predation could be detected for up to 8 h, when carabids fed on spiders immediately after the latter had consumed aphids. Beetles tested positive up to 4 h after eating spiders that had digested their aphid prey for 4 h. Clearly, the extreme sensitivity of PCR makes detection of secondary predation more likely, and the only reliable answer in future may be to use PCR to identify, in parallel, instances of intraguild predation
Meric et al. 2015 GBE: 83 novel Staphylococcus epidermidis genome assemblies
No full textZIP archive containing contigs for 83 whole genome sequences of S. epidermidis. Metadata is attached to the Dryad submission. Contact: Prof Samuel Sheppard [email protected]
Gene loss and lineage specific restriction-modification systems associated with niche differentiation in the Campylobacter jejuni Sequence Type 403 clonal complex
No full textCampylobacter jejuni is a highly diverse species of bacteria commonly associated with infectious intestinal disease of humans and zoonotic carriage in poultry, cattle, pigs, and other animals. The species contains a large number of distinct clonal complexes that vary from host generalist lineages commonly found in poultry, livestock, and human disease cases to host-adapted specialized lineages primarily associated with livestock or poultry. Here, we present novel data on the ST403 clonal complex of C. jejuni, a lineage that has not been reported in avian hosts. Our data show that the lineage exhibits a distinctive pattern of intralineage recombination that is accompanied by the presence of lineage-specific restriction-modification systems. Furthermore, we show that the ST403 complex has undergone gene decay at a number of loci. Our data provide a putative link between the lack of association with avian hosts of C. jejuni ST403 and both gene gain and gene loss through nonsense mutations in coding sequences of genes, resulting in pseudogene formation
54/08/13 Merrick Picks Judge Thomas To Preside
No full textIn a victory for Dr. Samuel H. Sheppard, Judge Merrick holds that Gershom M.M. Barber was prejudiced and not qualified to arraign Dr. Sam on a first degree murder charge. In turn, Merrick assigns Common Pleas Judge William K. Thomas to preside over the hearing.https://engagedscholarship.csuohio.edu/newspaper_coverage/1181/thumbnail.jp
54/08/13 Judge Thomas Esteemed for Fine Record, Tireless Devotion to Job
No full textAn article highlighting the career of Common Pleas Judge William K. Thomas (shown in the photo on the left). Thomas will conduct the preliminary hearing of Dr. Samuel H. Sheppard. Judge Frank J. Merrick (shown in the photo on the right) transferred the duty of the hearing from Magistrate Barber to Judge Thomas.https://engagedscholarship.csuohio.edu/newspaper_coverage/1182/thumbnail.jp
Do We Really Need Both BEKK and DCC? A Tale of Two Covariance Models
No full textLarge and very large portfolios of financial assets are routine for many individuals and organizations. The two most widely used models of conditional covariances and correlations are BEKK and DCC. BEKK suffers from the archetypal "curse of dimensionality" whereas DCC does not. This is a misleading interpretation of the suitability of the two models to be used in practice. The primary purposes of the paper are to define targeting as an aid in estimating matrices associated with large numbers of financial assets, analyze the similarities and dissimilarities between BEKK and DCC, both with and without targeting, on the basis of structural derivation, the analytical forms of the sufficient conditions for the existence of moments, and the sufficient conditions for consistency and asymptotic normality, and computational tractability for very large (that is, ultra high) numbers of financial assets, to present a consistent two step estimation method for the DCC model, and to determine whether BEKK or DCC should be preferred in practical applications.Conditional correlations, Conditional covariances, Diagonal models, Forecasting, Generalized models, Hadamard models, Scalar models, Targeting.
Do We Really Need Both BEKK and DCC? A Tale of Two Covariance Models
No full textLarge and very large portfolios of financial assets are routine for many individuals and organizations. The two most widely used models of conditional covariances and correlations are BEKK and DCC. BEKK suffers from the archetypal "curse of dimensionality" whereas DCC does not. This is a misleading interpretation of the suitability of the two models to be used in practice. The primary purposes of the paper are to define targeting as an aid in estimating matrices associated with large numbers of financial assets, analyze the similarities and dissimilarities between BEKK and DCC, both with and without targeting, on the basis of structural derivation, the analytical forms of the sufficient conditions for the existence of moments, and the sufficient conditions for consistency and asymptotic normality, and computational tractability for very large (that is, ultra high) numbers of financial assets, to present a consistent two step estimation method for the DCC model, and to determine whether BEKK or DCC should be preferred in practical applications.
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