Background: Bacteria of the genus Asaia have been recently recognized as secondary symbionts of different sugar-feeding insects, including the leafhopper Scaphoideus titanus, vector of Flavescence dorée phytoplasmas. Asaia has been shown to be localized in S. titanus gut, salivary glands and gonoducts and to be maternally transmitted to the progeny by an egg smearing mechanism. It is currently not known whether Asaia in S. titanus is transmitted by additional routes. We performed a study to evaluate if Asaia infection is capable of horizontal transmission via co-feeding and venereal routes. Results: A Gfp-tagged strain of Asaia was provided to S. titanus individuals to trace the transmission pathways of the symbiotic bacterium. Co-feeding trials showed a regular transfer of bacterial cells from donors to recipients, with a peak of frequency after 72 hours of exposure, and with concentrations of the administrated strain growing over time. Venereal transmission experiments were first carried out using infected males paired with uninfected females. In this case, female individuals acquired Gfp-labelled Asaia, with highest infection rates 72-96 hours after mating and with increasing abundance of the tagged symbiont over time. When crosses between infected females and uninfected males were conducted, the occurrence of female to male transmission was observed, even though the transfer occurred unevenly. Conclusions: The data presented demonstrate that the acetic acid bacterial symbiont Asaia is horizontally transmitted among S. titanus individuals both by co-feeding and venereal transmission, providing one of the few direct demonstrations of such a symbiotic transfer in Hemiptera. This study contributes to the understanding of the bacterial ecology in the insect host, and indicates that Asaia evolved multiple pathways for the colonization of S. titanus body.
Bibliographical noteFunding Information:
We are grateful to Greg Hurst for English editing of the manuscript. Financial contribution comes from the Italian Ministry for Research (MIUR), within the project PRIN 2007 “Caratterizzazione del microbiota associato a Scaphoideus titanus e Hyalesthes obsoletus, cicaline vettrici di fitoplasmi nella vite ed isolamento e studio della localizzazione di batteri acetici simbionti” and the project PRIN 2009 “Interazioni tra insetti vettori e microrganismi simbionti: nuove prospettive per il biocontrollo dei patogeni trasmessi alle piante, agli animali e all’uomo. The work has been performed in the frame of the project BIODESERT (European Community’s Seventh Framework Programme CSA-SA REGPOT-2008-2 under grant agreement 245746). E.G., E.C. and D.D. benefited of travel grants from Cost Action FA0701: “Arthropod Symbiosis: From Fundamental Studies to Pest and Disease Management”. This article has been published as part of BMC Microbiology Volume 11 Supplement 1, 2012: Arthropod symbioses: from fundamental studies to pest and disease mangement. The full contents of the supplement are available online at http://www.biomedcentral.com/1471-2180/12?issue=S1.
ASJC Scopus subject areas
- Microbiology (medical)