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ABSTRACT Vector mosquitoes are well‐adapted to habitats in urban areas, including belowground infrastructure such as stormwater systems. As a major source of larval habitat in population centers, control of larval populations in stormwater catch basins is an important tool for control of vector‐borne disease. Larval development and adult phenotypes driving vectorial capacity in mosquitoes are modulated by the larval gut microbiota, which is recruited from the aquatic environment in which larvae develop. Laboratory studies have quantified microbe‐mediated impacts on individual mosquito phenotypes, but more work is needed to characterise how microbiota variation shapes population‐level outcomes. Here, we evaluated the relationship between habitat microbiota variation and mosquito population dynamics by simultaneously characterising microbiota diversity, water quality, and mosquito productivity in a network of stormwater catch basins in the Chicago metropolitan area. High throughput sequencing of 16S rRNA gene amplicons from water samples collected from 60 basins over an entire mosquito breeding season detected highly diverse bacterial communities that varied with measures of water quality and over time. In situ measurements of mosquito abundance in the same basins further varied by microbiota composition and the relative abundance of specific bacterial taxa. Altogether, these results illustrate the importance of habitat microbiota in shaping ecological processes that affect mosquito populations. They also lay the foundation for future studies to characterise the mechanisms by which specific bacterial taxa impact individual and population‐level phenotypes related to mosquito vectorial capacity. 

Abstract Understanding microbial roles in ecosystem function requires integrating microscopic processes into food webs. The carnivorous pitcher plant,Sarracenia purpurea, offers a tractable study system where diverse food webs of macroinvertebrates and microbes facilitate digestion of captured insect prey, releasing nutrients supporting the food web and host plant. However, how interactions between these macroinvertebrate and microbial communities contribute to ecosystem functions remains unclear. We examined the role of the pitcher plant mosquito,Wyeomyia smithii, in top‐down control of the composition and function of pitcher plant microbial communities. Mosquito larval abundance was enriched or depleted across a natural population ofS. purpureapitchers over a 74‐day field experiment. Bacterial community composition and microbial community function were characterized by 16S rRNA amplicon sequencing and profiling of carbon substrate use, bulk metabolic rate, hydrolytic enzyme activity, and macronutrient pools. Bacterial communities changed from pitcher opening to maturation, but larvae exerted minor effects on high‐level taxonomic composition. Higher larval abundance was associated with lower diversity communities with distinct functions and elevated nitrogen availability. Treatment‐independent clustering also supported roles for larvae in curating pitcher microbial communities through shifts in community diversity and function. These results demonstrate top‐down control of microbial functions in an aquatic microecosystem. 

Abstract BackgroundMosquitoes harbor microbial communities that play important roles in their growth, survival, reproduction, and ability to transmit human pathogens. Microbiome transplantation approaches are often used to study host-microbe interactions and identify microbial taxa and assemblages associated with health or disease. However, no such approaches have been developed to manipulate the microbiota of mosquitoes. ResultsHere, we developed an approach to transfer entire microbial communities between mosquito cohorts. We undertook transfers between (Culex quinquefasciatustoAedes aegypti) and within (Ae. aegyptitoAe. aegypti) species to validate the approach and determine the number of mosquitoes required to prepare donor microbiota. After the transfer, we monitored mosquito development and microbiota dynamics throughout the life cycle. Typical holometabolous lifestyle-related microbiota structures were observed, with higher dynamics of microbial structures in larval stages, including the larval water, and less diversity in adults. Microbiota diversity in recipient adults was also more similar to the microbiota diversity in donor adults. ConclusionsThis study provides the first evidence for successful microbiome transplantation in mosquitoes. Our results highlight the value of such methods for studying mosquito-microbe interactions and lay the foundation for future studies to elucidate the factors underlying microbiota acquisition, assembly, and function in mosquitoes under controlled conditions. 

Abstract The mosquito microbiome is critical for host development and plays a major role in many aspects of mosquito biology. While the microbiome is commonly dominated by a small number of genera, there is considerable variation in composition among mosquito species, life stages, and geography. How the host controls and is affected by this variation is unclear. Using microbiome transplant experiments, we asked whether there were differences in transcriptional responses when mosquitoes of different species were used as microbiome donors. We used microbiomes from four different donor species spanning the phylogenetic breadth of the Culicidae, collected either from the laboratory or the field. We found that when recipients received a microbiome from a donor reared in the laboratory, the response was remarkably similar regardless of donor species. However, when the donor had been collected from the field, many more genes were differentially expressed. We also found that while the transplant procedure did have some effect on the host transcriptome, this is likely to have had a limited effect on mosquito fitness. Overall, our results highlight the possibility that variation in mosquito microbiome communities is associated with variability in host–microbiome interactions and further demonstrate the utility of the microbiome transplantation technique for investigating host–microbe interactions in mosquitoes. 

Abstract BackgroundThe leaves of carnivorous pitcher plants harbor diverse communities of inquiline species, including bacteria and larvae of the pitcher plant mosquito (Wyeomyia smithii), which aid the plant by processing captured prey. Despite the growing appreciation for this microecosystem as a tractable model in which to study food web dynamics and the moniker ofW. smithiias a ‘keystone predator’, very little is known about microbiota acquisition and assembly inW. smithiimosquitoes or the impacts ofW. smithii-microbiota interactions on mosquito and/or plant fitness. ResultsIn this study, we used high throughput sequencing of bacterial 16S rRNA gene amplicons to characterize and compare microbiota diversity in field- and laboratory-derivedW. smithiilarvae. We then conducted controlled experiments in the laboratory to better understand the factors shaping microbiota acquisition and persistence across theW. smithiilife cycle. Methods were also developed to produce axenic (microbiota-free)W. smithiilarvae that can be selectively recolonized with one or more known bacterial species in order to study microbiota function. Our results support a dominant role for the pitcher environment in shaping microbiota diversity inW. smithiilarvae, while also indicating that pitcher-associated microbiota can persist in and be dispersed by adultW. smithiimosquitoes. We also demonstrate the successful generation of axenicW. smithiilarvae and report variable fitness outcomes in gnotobiotic larvae monocolonized by individual bacterial isolates derived from naturally occurring pitchers in the field. ConclusionsThis study provides the first information on microbiota acquisition and assembly inW. smithiimosquitoes. This study also provides the first evidence for successful microbiota manipulation in this species. Altogether, our results highlight the value of such methods for studying host-microbiota interactions and lay the foundation for future studies to understand howW. smithii-microbiota interactions shape the structure and stability of this important model ecosystem. 

Abstract Microbiome research has gained considerable interest due to the emerging evidence of its impact on human and animal health. As in other animals, the gut-associated microbiota of mosquitoes affect host fitness and other phenotypes. It is now well established that microbes can alter pathogen transmission in mosquitoes, either positively or negatively, and avenues are being explored to exploit microbes for vector control. However, less attention has been paid to how microbiota affect phenotypes that impact vectorial capacity. Several mosquito and pathogen components, such as vector density, biting rate, survival, vector competence, and the pathogen extrinsic incubation period all influence pathogen transmission. Recent studies also indicate that mosquito gut-associated microbes can impact each of these components, and therefore ultimately modulate vectorial capacity. Promisingly, this expands the options available to exploit microbes for vector control by also targeting parameters that affect vectorial capacity. However, there are still many knowledge gaps regarding  mosquito–microbe interactions  that need to be addressed in order to exploit them efficiently. Here, we review current evidence of impacts of the microbiome on aspects of vectorial capacity, and we highlight likely opportunities for novel vector control strategies and areas where further studies are required. 

Mosquitoes transmit medically important human pathogens, including viruses like dengue virus and parasites such asPlasmodiumspp., the causative agent of malaria. Mosquito microbiomes are critically important for the ability of mosquitoes to transmit disease-causing agents. However, while large collections of bacterial isolates and genomic data exist for vertebrate microbiomes, the vast majority of work in mosquitoes to date is based on 16S rRNA gene amplicon data that provides limited taxonomic resolution and no functional information. To address this gap and facilitate future studies using experimental microbiome manipulations, we generated a bacterialMosquito-AssociatedIsolateCollection (MosAIC) consisting of 392 bacterial isolates with extensive metadata and high-quality draft genome assemblies that are publicly available, both isolates and sequence data, for use by the scientific community. MosAIC encompasses 142 species spanning 29 bacterial families, with members of theEnterobacteriaceaecomprising 40% of the collection. Phylogenomic analysis of 3 genera,Enterobacter,Serratia, andElizabethkingia, reveal lineages of mosquito-associated bacteria isolated from different mosquito species in multiple laboratories. Investigation into species’ pangenomes further reveals clusters of genes specific to these lineages, which are of interest for future work to test for functions connected to mosquito host association. Altogether, we describe the generation of a physical collection of mosquito-associated bacterial isolates, their genomic data, and analyses of selected groups in context of genome data from closely related isolates, providing a unique, highly valuable resource for research on bacterial colonisation and adaptation within mosquito hosts. Future efforts will expand the collection to include broader geographic and host species representation, especially from individuals collected from field populations, as well as other mosquito-associated microbes, including fungi, archaea, and protozoa.