Di nuovo sulle alternanze 'velari' nel verbo italiano e spagnolo.

Sin resume

From pure phonology to pure morphology the reshaping of the romance verb

This study deals with a significant morphological difference between Latin and Romance, namely that the latter has pervasive patterns of root-allomorphy absent from the former. Of particular interest here is the emergence of such allomorphy correlated with arbitrarily intersecting parameters of person, number, tense and mood in the verb. The alternations in question are, initially, the predictable consequences of regular sound changes. I argue that the phonological causation of this allomorphy is rapidly lost, and that the paradigmatic distribution of the resultant alternations is ‘morphomic’ in the sense of Aronoff (1994), lacking both phonological and morphosyntactic conditioning. These patterns provide an abstract paradigmatic template for wide-ranging and formally heterogeneous subsequent morphological changes across the Romance languages. But many scholars seek to analyse the resultant alternations in synchronically phonological terms, and some of the arguments adduced are powerful. This study reviews attempts to analyse in terms of phonological conditioning what I believe to be ‘morphomic’ alternations. While I defend the ‘morphomicity’ of the phenomena at issue, I also admit that the boundary between ‘morphomic’ and phonological phenomena may be less sharp than has usually been recognized.L’article étudie une différence morphologique très importante entre le latin et les langues romanes. Celles-ci se distinguent du latin par l’abondance des alternances du radical qui se manifestent surtout dans le verbe, où elles sont sensibles à des combinaisons arbitraires de traits de personne, de nombre, de temps et de mode. Bien qu’elles résultent d’effets réguliers du changement phonologique, je soutiendrai que ces alternances ont rapidement perdu leur motivation phonologique, pour devenir ‘morphomiques’ au sens d’Aronoff (1994) ; c’est-à-dire qu’elles manquent, sur le plan synchronique, de conditionnement soit phonologique soit morphosyntaxique. Ces alternances constituent en effet des schémas paradigmatiques abstraits, d’une importance remarquable pour l’histoire des langues romanes puisqu’elles constituent le modèle pour une série de changements ultérieurs au travers des langues romanes, dont le contenu phonologique se révèle souvent très hétérogène. Cependant, beaucoup de lingistes cherchent à en rendre compte en faisant appel à un conditionnement purement phonologique. Je passerai en revue quelques-unes de ces tentatives d’explication phonologique sur le plan synchronique : tout en défendant la nature ‘morphomique’ des alternances en question, je reconnaîtrai que la frontière entre la ‘morphocité’ et le conditionnement phonologique est peut-être plus floue qu’on ne l’a reconnu jusqu’à présent

Di nuovo sulle alternanze 'velari' nel verbo italiano e spagnolo.

Sin resume

Genealogical typing of Neisseria meningitidis

Despite the increasing popularity of multilocus sequence typing (MLST), the most appropriate method for characterizing bacterial variation and facilitating epidemiological investigations remains a matter of debate. Here, we propose that different typing schemes should be compared on the basis of their power to infer clonal relationships and investigate the utility of sequence data for genealogical reconstruction by exploiting new statistical tools and data from 20 housekeeping loci for 93 isolates of the bacterial pathogen Neisseria meningitidis. Our analysis demonstrated that all but one of the hyperinvasive isolates established by multilocus enzyme electrophoresis and MLST were grouped into one of six genealogical lineages, each of which contained substantial variation. Due to the confounding effect of recombination, evolutionary relationships among these lineages remained unclear, even using 20 loci. Analyses of the seven loci in the standard MLST scheme using the same methods reproduced this classification, but were unable to support finer inferences concerning the relationships between the members within each complex

The Impact of Nucleotide Sequence Analysis on Meningococcal Vaccine Development and Assessment

Since it became available as a routine tool in biology, the determination and analysis of nucleotide sequences has been applied to the design of vaccines and the investigation of their effectiveness. As vaccination is primarily concerned with the interaction of biological molecules with the immune system, the utility of sequence data is not immediately obvious and, indeed, nucleotide sequence data are most effective when used to complement more conventional immunological approaches. Here, the impact of sequencing on the field of vaccinology will be illustrated with reference to the development and implementation of vaccines against Neisseria meningitidis (the meningococcus) over the 30-year period from the late-1980s to the late-2010s. Nucleotide sequence-based studies have been important in the fight against this aggressive pathogen largely because of its high genetic and antigenic diversity, properties that were only fully appreciated because of sequence-based studies. Five aspects will be considered, the use of sequence data to: (i) discover vaccine antigens; (ii) assess the diversity and distribution of vaccine antigens; (iii) determine the evolutionary and population biology of the organism and their implications for immunization; and (iv) develop molecular approaches to investigate pre- and post-vaccine pathogen populations to assess vaccine impact. One of the great advantages of nucleotide sequence data has been its scalability, which has meant that increasingly large data sets have been available, which has proved invaluable in the investigation of an organism as diverse and enigmatic as the meningococcus

A chromosomally integrated bacteriophage in invasive meningococci

Cerebrospinal meningitis is a feared disease that can cause the death of a previously healthy individual within hours. Paradoxically, the causative agent, Neisseria meningitidis, is a common inhabitant of the human nasopharynx, and as such, may be considered a normal, commensal organism. Only in a small proportion of colonized people do the bacteria invade the bloodstream, from where they can cross the blood–brain barrier to cause meningitis. Furthermore, most meningococcal disease is caused by bacteria belonging to only a few of the phylogenetic groups among the large number that constitute the population structure of this genetically variable organism. However, the genetic basis for the differences in pathogenic potential remains elusive. By performing whole genome comparisons of a large collection of meningococcal isolates of defined pathogenic potential we brought to light a meningococcal prophage present in disease-causing bacteria. The phage, of the filamentous family, excises from the chromosome and is secreted from the bacteria via the type IV pilin secretin. Therefore, this element, by spreading among the population, may promote the development of new epidemic clones of N. meningitidis that are capable of breaking the normal commensal relationship with humans and causing invasive disease

Operationalising factors that explain the emergence of infectious diseases : A case study of the human campylobacteriosis epidemic

Peer reviewedPublisher PD

The domestication of the probiotic bacterium Lactobacillus acidophilus

Lactobacillus acidophilus is a Gram-positive lactic acid bacterium that has had widespread historical use in the dairy industry and more recently as a probiotic. Although L. acidophilus has been designated as safe for human consumption, increasing commercial regulation and clinical demands for probiotic validation has resulted in a need to understand its genetic diversity. By drawing on large, well-characterised collections of lactic acid bacteria, we examined L. acidophilus isolates spanning 92 years and including multiple strains in current commercial use. Analysis of the whole genome sequence data set (34 isolate genomes) demonstrated L. acidophilus was a low diversity, monophyletic species with commercial isolates essentially identical at the sequence level. Our results indicate that commercial use has domesticated L. acidophilus with genetically stable, invariant strains being consumed globally by the human population

Dam inactivation in Neisseria meningitidis: prevalence among diverse hyperinvasive lineages

BACKGROUND: DNA adenine methyltransferase (Dam) activity is absent in many, but not all, disease isolates of Neisseria meningitidis, as a consequence of the insertion of a restriction endonuclease-encoding gene, the 'dam replacing gene' (drg) at the dam locus. Here, we report the results of a survey to assess the prevalence of drg in a globally representative panel of disease-associated meningococci. RESULTS: Of the known meningococcal hyper-invasive lineages investigated, drg was absent in all representatives of the ST-8 and ST-11 clonal complexes tested, but uniformly present in the representatives of the other hyper-invasive lineages present in the isolate collection (the ST-1, ST-4, ST-5, ST-32 and ST-41/44 clonal complexes). The patterns of sequence diversity observed in drg were consistent with acquisition of this gene from a source organism with a different G+C content, at some time prior to the emergence of present-day meningococcal clonal complexes, followed by spread through the meningococcal population by horizontal genetic exchange. During this spread a number of alleles have arisen by mutation and intragenic recombination. CONCLUSION: These findings are consistent with the idea that possession of the drg gene may contribute to the divergence observed among meningococcal clonal complexes, but does not have a direct mechanistic involvement in virulence

Plural formation in Istro-Romanian numeral quantifier phrases: inflexional calquing from Croatian?

We explore the effects of prolonged contact with Croatian on the inflexional morphology of number-marking in the Istro-Romanian noun. One result of a reorganization of the nominal system is that certain bisyllabic plural desinences, originally associated with feminine gender, are reassigned to the masculine, and come to exist alongside other modes of masculine plural marking. The resultant variation in masculine plural inflexion becomes subject to new patterns of distribution which are clearly sensitive to Croatian models, including the exaptation of masculine plural morphology to provide distinctive specialized morphological marking of plurals in certain numeral quantifier expressions for ‘smaller’ numbers, in ways clearly reminiscent of Croatian. What is involved is a complex array of ‘pattern’ borrowing, although there is also some evidence for ‘matter’ borrowing of a dialectal Croatian plural ending which Istro-Romanian sometimes uses in numeral quantifier phrases with higher numerals. Overall, we seem to be in the presence of an emergent ‘numerative’. While the creation of numeratives is well known from the internal history of various languages, our data may show that they may also emerge through language contact