Molecular, cellular and phylogenetic characterization of Wolbachia in Aedes africanus confirms symbionts competition with Pantoea vagans

Background : Wolbachia is an endosymbiotic bacterium that naturally infects several arthropod and nematode species. Wolbachia gained significant attention in the last couple of decades, due to its impact on host fitness and the ability of specific Wolbachia strains to interfere with vectorial capacity in mosquitoes or to sterilise insect females. These characteristics have been exploited in pest and vector management and in the control of vector-borne diseases. Wolbachia presence in insect species is variable, with species presenting 100% positive individuals in all sampled populations, and others that present a patchy distribution, with variable prevalences in different populations. Factors that might influence Wolbachia infection rate in insect populations have not yet been investigated in all respects. In addition, there might be limits in the methods used for Wolbachia detection. Results: Through an integrated technical approach, we recently detected and identified Wolbachia in the African bush and forest-associated mosquito Aedes africanus . Investigations on the microbiota of Ae. africanus , and phylogenomics on its Wolbachia , highlighted some peculiarities. First, Wolbachia from Ae. africanus is closer to the wolbachiae of other insects, rather than to those generally found in mosquitoes. Second, metagenomics uncovered a phenomenon of microbial competition between Wolbachia and Pantoea vagans within Ae. africanus . Conclusions: The use of Wolbachia in the fight against MBD cannot ignore the characterization of the bacterium in the specific host vector and the knowledge of any competition mechanisms; this to select both the phenotypes most suitable for suppressing pathogen transmission and those to be used in manipulating host reproduction. The mutual negative interference between Wolbachia and Pantoea for the colonisation of Ae. africanus , underlines how interactions between symbionts in the vector host can influence the effectiveness of control methods based on the use of Wolbachia . Our results pinpoint that the possible use of Wolbachia for the control of MBDs must take into due account both the genetic background of the host mosquito, we know in fact that the same strain of Wolbachia can induce different phenomena in the host, and the architecture of its microbiota that can interact in various ways with Wolbachia .