Abstract
The mosquito body hosts highly diverse microbes, which influence different physiological traits of both larvae and adults. The composition of adult mosquito microbiota is tightly linked to that of larvae, which are aquatic and feed on organic detritus, algae and prokaryotic microorganisms present in their breeding sites. Unraveling the ecological features of larval habitats that shape the structure of bacterial communities and their interactions with the mosquito host is still a poorly investigated topic in the Asian tiger mosquito Aedes albopictus, a highly invasive species that is vector of numerous arboviruses, including Dengue, Chikungunya, and Zika viruses. In this study, we investigated the composition of the bacterial community present in the water from a natural larval breeding site in which we separately reared wild-collected larvae and hatched eggs of the Foshan reference laboratory strain. Using sequence analysis of bacterial 16S rRNA gene amplicons, we comparatively analyzed the microbiota of the larvae and that of adult mosquitoes, deriving information about the relative impact of the breeding site water on shaping mosquito microbiota. We observed a higher bacterial diversity in breeding site water than in larvae or adults, irrespective of the origin of the sample. Moreover, larvae displayed a significantly different and most diversified microbial community than newly emerged adults, which appeared to be dominated by Proteobacteria. The microbiota of breeding site water significantly increased its diversity over time, suggesting the presence of a dynamic interaction among bacterial communities, breeding sites and mosquito hosts. The analysis of Wolbachia prevalence in adults from Foshan and five additional strains with different geographic origins confirmed the described pattern of dual wAlbA and wAlbB strain infection. However, differences in Wolbachia prevalence were detected, with one strain from La Reunion Island showing up to 18% uninfected individuals. These findings contribute in further understanding the dynamic interactions between the ecology of larval habitats and the structure of host microbiota, as well as providing additional information relative to the patterns of Wolbachia infection.
Highlights
We addressed three main questions: (i) to what extent is the breeding site microbiota affecting endosymbiont community assemblage in larval and adult Ae. albopictus? (ii) Is the bacterial community of the breeding site water changing over time during mosquito development? (iii) What is the frequency of Wolbachia in adult samples reared as larvae in the wild-collected water?
Water from Ae. albopictus larval breeding sites was collected in a private garden in Crema, Italy (45◦21 51.2 N 9◦40 57.7 E), which was an accessible site characterized by high population density, at the end of August 2018, when climate conditions are optimal for mosquito development
The analysis of the diversity of bacterial communities showed that Ae. albopictus larvae contain a subset of the Amplicon Sequence Variants (ASVs) present in breeding site water, supporting the idea that larvae are colonized by a fraction of the bacteria ingested through feeding (Minard et al, 2013; Coon et al, 2016b; Strand, 2018)
Summary
The microbiota of Aedes mosquitoes is known to play a significant role in host physiology, including egg production, blood digestion (Gaio Ade et al, 2011; Coon et al, 2016a), immunity regulation (Xi et al, 2008), host–pathogen interaction and vector competence (Ramirez et al, 2012; Charan et al, 2013; Goncalves et al, 2014; Dickson et al, 2017; Souza-Neto et al, 2019) The microbiota of both laboratory and wild Aedes mosquitoes has been investigated and shown to be dominated by Proteobacteria (Wang et al, 2018). These findings indicate the importance of the environment in shaping mosquito microbiota
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