Ticks are capable of transmitting various pathogens. One example is bacteria of the genus Ehrlichia which are capable of causing ehrlichiosis in numerous animals and humans, posing a significant medical risk. Ehrlichia muris, although rarely, is capable of infecting humans, and producing symptoms similar to those caused by ehrlichiosis of other Ehrlichia species . The presence of Ehrlichia muris in Italy has never been confirmed until now, and in general its distribution in Europe is still poorly known. Thanks to the finding of a thrush in northern Italy, parasitized by a tick belonging to the Ixodes ricinus species, the presence of Ehrlichia muris within the arthropod was confirmed by PCR. The genome was then extracted from the tick and sequenced. One of the objectives of this thesis was to isolate in silico from the tick metagenome and assemble the first genome of Ehrlichia muris of European, and specifically Italian, origin. Subsequently, several comparative genomics analyses were made among different species of Ehrlichia muris, and among several other Ehrlichia sp. species. Phylogenomic analyses were conducted to establish the phylogenetic distance with other E. muris, and to verify whether it was a new subspecies or belonged to the same subspecies in the Japanese genome. Finally, despite the great similarity of this genome with those of the other two Ehrlichia muris, through phylogenetic analysis, variations in some genes between the new genome and the previous ones were detected. In particular, proteins known to play a role in host cell infection and disease development were taken into account, allowing a greater understanding of the evolution of these pathogens and their population genomics.
Le zecche sono in grado di trasmettere diversi patogeni. Un esempio sono i batteri del genere Ehrlichia i quali sono in grado di causare l’ehrlichiosi in numerosi animali e nell’essere umano, costituendo un rischio medico significativo. Ehrlichia muris, seppur raramente, è in grado di infettare l’uomo, e di produrre sintomi simili a quelli causati dalle ehrlichiosi di altre specie di Ehrlichia . La presenza di Ehrlichia muris in Italia non è mai stata confermata fino ad ora, e in generale la sua distribuzione in Europa è ancora poco conosciuta. Grazie al ritrovamento di un tordo nel nord Italia, parassitato da una zecca appartenente alla specie di Ixodes ricinus, è stata confermata la presenza di Ehrlichia muris all’interno dell’artropode tramite PCR. Il genoma è stato quindi estratto dalla zecca e sequenziato. Uno degli obiettivi di questa tesi è stato quello di isolare in silico dal metagenoma della zecca e di assemblare il primo genoma di Ehrlichia muris di origine europea, e in particolare italiana. Successivamente sono state fatte diverse analisi di genomica comparativa tra le diverse specie di Ehrlichia muris, e tra numerose altre specie di Ehrlichia sp.. Sono state condotte analisi filogenomiche per stabilire la distanza filogenetica con gli altri E. muris, e verificare se si trattasse di una nuova sottospecie oppure se appartenesse alla stessa sottospecie del genoma giapponese. Infine, nonostante la grande similitudine di questo genoma con quelli degli altri due Ehrlichia muris, tramite analisi filogenetiche sono state rilevate le variazioni di alcuni geni tra il nuovo genoma e quelli precedenti. In particolare sono state prese in considerazione proteine note per il loro ruolo nell’infezione delle cellule ospiti e nello sviluppo della patologia, consentendo una comprensione maggiore dell’evoluzione di questi patogeni e della loro genomica di popolazione.
Analisi genomiche di Ehrlichia muris, batterio patogeno trasmesso da zecche
ERRIQUEZ, LUCA
2022/2023
Abstract
Ticks are capable of transmitting various pathogens. One example is bacteria of the genus Ehrlichia which are capable of causing ehrlichiosis in numerous animals and humans, posing a significant medical risk. Ehrlichia muris, although rarely, is capable of infecting humans, and producing symptoms similar to those caused by ehrlichiosis of other Ehrlichia species . The presence of Ehrlichia muris in Italy has never been confirmed until now, and in general its distribution in Europe is still poorly known. Thanks to the finding of a thrush in northern Italy, parasitized by a tick belonging to the Ixodes ricinus species, the presence of Ehrlichia muris within the arthropod was confirmed by PCR. The genome was then extracted from the tick and sequenced. One of the objectives of this thesis was to isolate in silico from the tick metagenome and assemble the first genome of Ehrlichia muris of European, and specifically Italian, origin. Subsequently, several comparative genomics analyses were made among different species of Ehrlichia muris, and among several other Ehrlichia sp. species. Phylogenomic analyses were conducted to establish the phylogenetic distance with other E. muris, and to verify whether it was a new subspecies or belonged to the same subspecies in the Japanese genome. Finally, despite the great similarity of this genome with those of the other two Ehrlichia muris, through phylogenetic analysis, variations in some genes between the new genome and the previous ones were detected. In particular, proteins known to play a role in host cell infection and disease development were taken into account, allowing a greater understanding of the evolution of these pathogens and their population genomics.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/17007