1,720,954 research outputs found
Symbiotic and associated bacteria in Tephritid flies
Full text linkThe Tephritidae family, commonly known as “fruit flies”, is a large Dipteran family. It includes many notorious agricultural pests, as the olive fly (Bactrocera oleae), the cherry fruit fly (Rhagoletis cerasi) and the walnut husk fly (R. completa).
The importance of bacteria in the life history of fruit flies is well-known. In the beginning of last century Petri (1909) was the first to report the presence of symbiotic bacteria within the olive fruit fly (Bactrocera oleae); recently it was designated as “Candidatus Erwinia dacicola”. In Tephritids flies, the bacteria are housed in the midgut and in a specialized intestinal diverticulum, located in the fly head, called oesophageal bulb.
In this thesis, some aspects of the relationship between the above mentioned Tephritid flies and bacteria has been investigated, such as the microflora composition, the symbiont genetic variability and the bacterial transmission.
The thesis is composed of five studies.
The first study analyzes in details the genetic variability of Ca. E. dacicola in various Italian olive fly populations, studying the 16S rRNA gene. The presence of only two symbiont lineages, not coexisting in the same fly individual, was clearly noticed. Interestingly, the olive fly populations of the two main Italian islands, Sicily and Sardinia, are exclusively represented by one of the two lineages, which could suggest a non-random distribution. On the other hand, the peninsular populations show both bacterial haplotypes, in different proportions. No significant correlation was found between the two symbiont haplotypes and the observed host fly haplotypes, providing evidences for a mixed model of vertical and horizontal transmission of the symbiont during the fly life cycle.
The second study extends the previous study to a wider range. The presence of only two symbiont haplotypes was still confirmed for the Mediterranean and African populations. Surprisingly the symbiont haplotypes seem to be more related to the territory than the numerous host haplotypes.
The third study deals with the identification of the microflora composition of R. completa and R. cerasi. All the life stages of the cherry fruit fly and the adult stage in R. completa have been taken into account, using both culture dependent and independent methods. Bacteria detected within the oesophageal bulbs of both species are affiliated to Enterobacteriaceae family. The results on the bacterial transmission show a different mechanisms respect to the olive fly and the subfamily Tephritinae symbionts.
In the fourth study, the Klebsiella spp. strains isolated from the oesophageal bulb of R. completa and Ceratitis capitata were examined for their ability to incorporate the gene encoding green fluorescent protein (GFP). These bacteria were successfully labelled by conjugation with the gfp gene and the gfp gene was stably maintained in the transgenic strains. Moreover, the colonizing ability of gfp-tagged bacteria in the original host was tested. Here a non-invasive technique to monitor the bacterial fate during the fly life stages was used. Gfp-tagged bacteria were successfully ingested by walnut husk flies where they established a stable population in the fly gut over time and throughout developmental stages. This is the first report in Tephritid flies of native engineered bacteria re-introduced in its original host and the shuttle system used in this study could be a useful tool to expand and strengthen the possibility of biological control of the insect pest.
The last study is part of Isabel Martinez-Sañudo PhD thesis, for which I contributed to experimental works. The main goal of this study was to analyse the phylogenetic relationships between flies of the Tephritinae subfamily and their symbiotic bacteria. Some species of this subfamily are in effect known to host specific non-culturable symbiont bacteria (‘‘Candidatus Stammerula spp.”) in their midgut. The cophylogenetic analysis reveals the presence of congruence, even if imperfect, between hosts and symbionts. This non-strict congruence is probably due to events such as losses, duplications and hosts switching, which are likely to arise during the biological cycle of the fly in consideration of the extracellular status of these symbionts.I Tefritidi, noti anche come “fruit fly”, rappresentano una vasta famiglia di Ditteri comprendenti specie dannose per l’agricoltura quali la mosca dell’olivo (Bactrocera oleae), la mosca del ciliegio (Rhagoletis cerasi), la mosca del noce (R. completa) e la mosca mediterranea della frutta (Ceratitis capitata).
L’importanza delle associazioni batteriche nella famiglia dei Tefritidi è nota sin da quando Petri, all’inizio del secolo scorso, riportò la presenza di un battere simbionte, in seguito designato “Candidatus Erwinia dacicola”, in un diverticolo del capo della mosca dell’olivo chiamato bulbo esofageo. I successivi studi hanno evidenziato, sia con metodi tradizionali, sia con un approccio di tipo molecolare, lo stretto legame esistente tra batteri e tefritidi, siano essi simbionti ereditari e coevoluti e non coltivabili o semplici batteri associati.
Nel presente lavoro sono stati analizzati in dettaglio alcuni aspetti delle relazioni batteriche in alcune specie di tefritidi, quali la variabilità genetica dei simbionti, la composizione della microflora batterica e la presenza di trasmissione attraverso i diversi stadi di sviluppo dell’ospite. La tesi si articola in cinque capitoli.
Il primo lavoro analizza la variabilità genetica nel battere simbionte di B. oleae “Ca. Erwinia dacicola” in diverse popolazioni italiane della mosca dell’olivo, usando il gene ribosomale 16S come marcatore. Lo studio ha evidenziato la presenza di soli due aplotipi del simbionte, evidenziando anche che la loro presenza contemporanea all’interno di uno stesso ospite sembra in base a tutti i reperti non essere non essere probabile. La distribuzione di queste due linee batteriche nelle popolazioni di B. oleae sembra inoltre non essere casuale, poiché le popolazioni delle due maggiori isole italiane (Sardegna e Sicilia) ospitano uno o l’altro dei due aplotipi. Al contrario, le popolazioni della penisola ospitano, in proporzioni significativamente diverse, entrambi gli aplotipi del simbionte. Non è emersa una correlazione tra gli aplotipi di “Ca. E. dacicola” e gli aplotipi mitocondriali del loro ospite. Tale risultato potrebbe essere spiegato ammettendo l’esistenza, oltre alla prevalente trasmissione verticale, di accidentali passaggi orizzontali del simbionte.
Nel secondo lavoro l’indagine è stata estesa a un areale più ampio circummediterraneo della mosca dell’olivo. I due aplotipi di “Ca Erwinia dacicola” rinvenuti in Italia sono stati riscontrati con frequenze diverse anche in Africa. Inaspettatamente gli aplotipi del simbionte risultano essere più correlati al territorio di quanto non lo siano i numerosi aplotipi mitocondriali dell’ospite.
Nel terzo lavoro è stata indagata la composizione della microflora di R. completa e R. cerasi prelevate in natura, analizzandone i diversi stadi di sviluppo sia con approccio tradizionale coltura-dipendente che con approccio molecolare coltura-indipendente. Dal lavoro è emerso che le entità batteriche predominanti presenti nel bulbo esofageo appartengono alla famiglia delle Enterobacteriaceae. I risultati ottenuti evidenziano un meccanismo di trasmissione dei batteri diverso da quello evidenziato per i simbionti della mosca dell’olivo e della sottofamiglia Tephritinae.
Nel quarto lavoro è stata studiata l’abilità di ceppi di Klebsiella isolati originariamente dal bulbo esofageo di R. completa e C. capitata di incorporare il gene per l’espressione di una proteina fluorescente (GFP) e quindi la capacità del battere cosi modificato di ri-colonizzare l’ospite originario. Questa tecnica non distruttiva ha consentito il monitoraggio del destino dei batteri nel corso degli stadi di sviluppo dell’insetto. I batteri modificati sono stai ingeriti con successo dalle mosche del noce e ne hanno colonizzato in modo stabile l’intestino medio allo stadio di larva e quindi nella pupa. Si tratta del primo caso in cui un battere tipico della microflora di un tefritide è stato ingegnerizzato con successo e quindi introdotto nell’ospite nativo. La tecnica utilizzata in questo studio potrebbe costituire un valido strumento per espandere questo tipo di ricerca anche al controllo biologico di altre specie dannose in agricoltura.
L’ultimo lavoro fa parte parzialmente della tesi di dottorato della Dott.ssa Isabel Martinez-Sañudo, per il quale ho contribuito nella parte sperimentale. L’obbiettivo principale di questo studio è stato quello di indagare le relazioni filogenetiche tra le mosche della sottofamiglia delle Tefritine e i loro batteri simbionti. Alcune specie di questa sottofamiglia sono infatti note per ospitare un simbionte specifico ereditario e non coltivabile (‘‘Candidatus Stammerula spp.”) nell’intestino medio. Tali batteri simbionti sono presenti solo in due delle cinque tribù della sottofamiglia studiate. L’analisi della cofilogenesi ha rivelato la presenza di una congruenza, seppure imperfetta, tra ospiti e simbionti
Duplication polymorphism at MHC class II DRB1 locus in the wild boar (Sus scrofa).
No full textAB The origin of allelic polymorphism in genes of the major histocompatibility complex represents a central topic in evolutionary genetics as it is probably the most polymorphic region in the nuclear genome of vertebrates. Accordingly, the analyses of genetic variability at these loci provide evidence complementary to the population genetics studies based on neutral loci. In this study, four wild boar populations, two from Italy (Florence region and Castelporziano Presidential Reserve, outside Rome) and one each from Hungary and Poland, were characterized at a highly polymorphic fragment including part of intron 1 and exon 2 of swine leukocyte antigen (SLA) class II DRB1 gene by direct sequencing and by cloning. Excluding the false alleles, a total of 18 different sequences were observed in 57 individuals. The high ratio of nonsynonymous (dN) vs synonymous (dS) substitution rates in the peptide-binding region supports the hypothesis that balancing selection is operating at this locus. A duplication event at the DRB1 gene was documented only in one Italian population with both copies being putatively active. This is the first evidence of a polymorphism for the number of copies of an SLA gene
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
