Torix group <em>Rickettsia</em> are widespread in <em>Culicoides</em> biting midges (Diptera: Ceratopogonidae), reach high frequency and carry unique genomic features
2017
Pilgrim, Jack | Ander, Mats | Garros, Claire | Baylis, M. | Hurst, Gregory D. D. | Siozios, Stefanos | University of Liverpool | National Veterinary Institute | Animal, Santé, Territoires, Risques et Ecosystèmes (UMR ASTRE) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA) | NIHR Health Protection Research Unit in Emerging and Zoonotic Infections | his work was supported by a Marie Curie Individual Fellowship (H2020-MSCA-IF-2014) grant 657135 'MIDGESYM' to Stefanos Siozios and a BBSRC DTP studentship to Jack Pilgrim. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, the Department of Health or Public Health England
International audience
Show more [+] Less [-]English. There is increasing interest in the heritable bacteria of invertebrate vectors of disease as they present novel targets for control initiatives. Previous studies on biting midges (Culicoides spp.), known to transmit several RNA viruses of veterinary importance, have revealed infections with the endosymbiotic bacteria, Wolbachia and Cardinium. However, rickettsial symbionts in these vectors are underexplored. Here, we present the genome of a previously uncharacterized Rickettsia endosymbiont from Culicoides newsteadi (RiCNE). This genome presents unique features potentially associated with host invasion and adaptation, including genes for the complete non-oxidative phase of the pentose phosphate pathway, and others predicted to mediate lipopolysaccharides and cell wall modification. Screening of 414 Culicoides individuals from 29 Palearctic or Afrotropical species revealed that Rickettsia represent a widespread but previously overlooked association, reaching high frequencies in midge populations and present in 38% of the species tested. Sequence typing clusters the Rickettsia within the Torix group of the genus, a group known to infect several aquatic and hematophagous taxa. FISH analysis indicated the presence of Rickettsia bacteria in ovary tissue, indicating their maternal inheritance. Given the importance of biting midges as vectors, a key area of future research is to establish the impact of this endosymbiont on vector competence.
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