Mosquitoes (Diptera: Culicidae) have been shown to host diverse bacterial communities that vary depending on the sex of the mosquito, the developmental stage, and ecological factors. Some studies have suggested a potential role of microbiota in the nutritional, developmental and reproductive biology of mosquitoes. Here, we present a review of the diversity and functions of mosquito-associated bacteria across multiple variation factors, emphasizing recent findings. Mosquito microbiota is considered in the context of possible extended phenotypes conferred on the insect hosts that allow niche diversification and rapid adaptive evolution in other insects. These kinds of observations have prompted the recent development of new mosquito control methods based on the use of symbiotically-modified mosquitoes to interfere with pathogen transmission or reduce the host life span and reproduction. New opportunities for exploiting bacterial function for vector control are highlighted.

The holobiont concept was first developed for coral ecosystems but has been extended to multiple organisms, including plants and other animals. Studies on insect-associated microbial communities have produced strong evidence that symbiotic bacteria play a major role in host biology. However, the understanding of these symbiotic relationships has mainly been limited to phytophagous insects, while the role of host-associated microbiota in haematophagous insect vectors remains largely unexplored. Mosquitoes are a major global public health concern, with a concomitant increase in people at risk of infection. The global emergence and re-emergence of mosquito-borne diseases has led many researchers to study both the mosquito host and its associated microbiota. Although most of these studies have been descriptive, they have led to a broad description of the bacterial communities hosted by mosquito populations. This review describes key advances and progress in the field of the mosquito microbiota research while also encompassing other microbes and the environmental factors driving their composition and diversity. The discussion includes recent findings on the microbiota functional roles and underlines their interactions with the host biology and pathogen transmission. Insight into the ecology of multipartite interactions, we consider that conferring the term holobiont to the mosquito and its microbiota is useful to get a comprehensive understanding of the vector pathosystem functioning so as to be able to develop innovative and efficient novel vector control strategies.

Conditions experienced during larval development of holometabolous insects can affect adult traits, but whether differences in the bacterial communities of larval development sites contribute to variation in the ability of insect vectors to transmit human pathogens is unknown. We addressed this question in the mosquito Aedes aegypti, a major arbovirus vector breeding in both sylvatic and domestic habitats in Sub-Saharan Africa. Targeted metagenomics revealed differing bacterial communities in the water of natural breeding sites in Gabon. Experimental exposure to different native bacterial isolates during larval development resulted in significant differences in pupation rate and adult body size but not life span. Larval exposure to an Enterobacteriaceae isolate resulted in decreased antibacterial activity in adult hemolymph and reduced dengue virus dissemination titer. Together, these data provide the proof of concept that larval exposure to different bacteria can drive variation in adult traits underlying vectorial capacity. Our study establishes a functional link between larval ecology, environmental microbes, and adult phenotypic variation in a holometabolous insect vector.

The Asian tiger mosquito Aedes albopictus is currently one of the most threatening invasive species in the world. Native to Southeast Asia, the species has spread throughout the world in the past 30 years and is now present in every continent but Antarctica. Because it was the main vector of recent Dengue and Chikungunya outbreaks, and because of its competency for numerous other viruses and pathogens such as the Zika virus, A. albopictus stands out as a model species for invasive diseases vector studies. A synthesis of the current knowledge about the genetic diversity of A. albopictus is needed, knowing the interplays between the vector, the pathogens, the environment and their epidemiological consequences. Such resources are also valuable for assessing the role of genetic diversity in the invasive success. We review here the large but sometimes dispersed literature about the population genetics of A. albopictus. We first debate about the experimental design of these studies and present an up-to-date assessment of the available molecular markers. We then summarize the main genetic characteristics of natural populations and synthesize the available data regarding the worldwide structuring of the vector. Finally, we pinpoint the gaps that remain to be addressed and suggest possible research directions.

The Asian tiger mosquito Aedes albopictus is one of the most significant pathogen vectors of the 21st century. Originating from Asia, it has invaded a wide range of eco-climatic regions worldwide. The insect-associated microbiota is now recognized to play a significant role in host biology. While genetic diversity bottlenecks are known to result from biological invasions, the resulting shifts in host-associated microbiota diversity has not been thoroughly investigated. To address this subject, we compared four autochthonous Ae. albopictus populations in Vietnam, the native area of Ae. albopictus, and three populations recently introduced to Metropolitan France, with the aim of documenting whether these populations display differences in host genotype and bacterial microbiota. Population-level genetic diversity (microsatellite markers and COI haplotype) and bacterial diversity (16S rDNA metabarcoding) were compared between field-caught mosquitoes. Bacterial microbiota from the whole insect bodies were largely dominated by Wolbachia pipientis. Targeted analysis of the gut microbiota revealed a greater bacterial diversity in which a fraction was common between French and Vietnamese populations. The genus Dysgonomonas was the most prevalent and abundant across all studied populations. Overall genetic diversities of both hosts and bacterial microbiota were significantly reduced in recently established populations of France compared to the autochthonous populations of Vietnam. These results open up many important avenues of investigation in order to link the process of geographical invasion to shifts in commensal and symbiotic microbiome communities, as such shifts may have dramatic impacts on the biology and/or vector competence of invading hematophagous insects.

The presence of cultivable bacteria Acinetobacter and Asaia was recently demonstrated in the mosquito vector Aedes albopictus. However, it is not kno