INTRODUCTION. Symbiosis between bacteria and arthropods is considered a relevant driver of their evolution (McCutcheon and Moran, 2011, Nat. Rev. Microbiol. 10, 13–26). A wide range of tick species harbour bacterial endosymbionts in various tissues, many of them playing important roles in the fitness and biology of their hosts, in the modulation of their vectorial ability and their chemical acaricides resistance. The females of Ixodes ricinus (Ixodidae), the most common hard tick in Europe and vector of tick borne zoonoses, harbour the intracellular endosymbiont Midichloria mitochondrii (order Rickettsiales) with a 100% prevalence, suggesting a mutualistic relationship. Considering that the tissue distribution of a symbiont might be indicative of its functional role in the physiology of the host, we investigated M. mitochondrii specific localization pattern and the relative quantification in selected organs of I. ricinus. MATERIALS AND METHODS. We dissected salivary glands, gut, ovary, rostrum, tracheae and Malpighian tubules from unengorged and semi-engorged I. ricinus ticks. As negative control, we used the tick Pholeoixodes hexagonus (Ixodidae), that does not harbour M. mitochondrii, collected from cats in the same area. The dissected organs were then subjected to Real Time PCR (qPCR) to quantify M. mitochondrii (Sassera et al., 2008, Appl. Environ. Microbiol. 74, 6138–6140). Midichloria-rich organs were then subjected to specific immunofluorescence assay. RESULTS AND CONCLUSION. M. mitochondrii was abundant in ovaries, Malpighian tubules and salivary glands of semi-engorged I. ricinus and in ovaries and tracheae of unengorged I. ricinus. Immunofluorescence performed on ovaries shows that the symbiont cells occupy most of the oocytes cytoplasm, suggesting a role of the bacterium in the host reproduction. In the Malpighian tubules, M. mitochondrii was detected in the proximal region of the tubules, indicating a potential role in the maintenance of homeostasis, water balance, excretion, and in the detoxification processes. Furthermore, the localization in the salivary glands is coherent with our previous hypotheses of horizontal transmission of M. mitochondrii. Analysis of the metabolic pathways of M. mitochondrii is underway to identify host supportive functions.
Midichloria mitochondrii localization and quantification in the organs of the hard tick Ixodes ricinus / E. Olivieri, I. VAROTTO BOCCAZZI, C. Romeo, A. Desirò, A. Cafiso, V. Serra, A.M. Floriano, S. Epis, D. Sassera - In: Atti del XXX Congresso della Società Italiana di Parassitologia (SoIPa)[s.l] : Società Italiana di Parassitologia, 2018. - ISBN 9788894357509. - pp. 172-172 (( Intervento presentato al 30. convegno Congresso della Società Italiana di Parassitologia (SoIPa) tenutosi a Milano nel 2018.
|Titolo:||Midichloria mitochondrii localization and quantification in the organs of the hard tick Ixodes ricinus|
|Parole Chiave:||Symbiosis; Midichloria mitochondrii; Ixodes ricinus|
|Settore Scientifico Disciplinare:||Settore VET/06 - Parassitologia e Malattie Parassitarie degli Animali|
|Data di pubblicazione:||2018|
|Tipologia:||Book Part (author)|
|Appare nelle tipologie:||03 - Contributo in volume|