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1. A cryopreservation method to recover laboratory- and field-derived bacterial communities from mosquito larval habitats

   https://doi.org/10.1371/journal.pntd.0011234  

   Zhao, Serena Y.; Hughes, Grant L.; Coon, Kerri L. (April 2023, PLOS Neglected Tropical Diseases)

   Bartholomay, Lyric C. (Ed.)

   Mosquitoes develop in a wide range of aquatic habitats containing highly diverse and variable bacterial communities that shape both larval and adult traits, including the capacity of adult females of some mosquito species to transmit disease-causing organisms to humans. However, while most mosquito studies control for host genotype and environmental conditions, the impact of microbiota variation on phenotypic outcomes of mosquitoes is often unaccounted for. The inability to conduct reproducible intra- and inter-laboratory studies of mosquito-microbiota interactions has also greatly limited our ability to identify microbial targets for mosquito-borne disease control. Here, we developed an approach to isolate and cryopreserve bacterial communities derived from lab and field-based larval rearing environments of the yellow fever mosquito Aedes aegypti –a primary vector of dengue, Zika, and chikungunya viruses. We then validated the use of our approach to generate experimental microcosms colonized by standardized lab- and field-derived bacterial communities. Our results overall reveal minimal effects of cryopreservation on the recovery of both lab- and field-derived bacteria when directly compared with isolation from non-cryopreserved fresh material. Our results also reveal improved reproducibility of bacterial communities in replicate microcosms generated using cryopreserved stocks over fresh material. Communities in replicate microcosms further captured the majority of total bacterial diversity present in both lab- and field-based larval environments, although the relative richness of recovered taxa as compared to non-recovered taxa was substantially lower in microcosms containing field-derived bacteria. Altogether, these results provide a critical next step toward the standardization of mosquito studies to include larval rearing environments colonized by defined microbial communities. They also lay the foundation for long-term studies of mosquito-microbe interactions and the identification and manipulation of taxa with potential to reduce mosquito vectorial capacity. 

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2. Microplastic ingestion perturbs the microbiome of Aedes albopictus (Diptera: Culicidae) and Aedes aegypti

   https://doi.org/10.1093/jme/tjad097  

   Edwards, Carla-Cristina; McConnel, Gabriella; Ramos, Daniela; Gurrola-Mares, Yaizeth; Dhondiram Arole, Kailash; Green, Micah J; Cañas-Carrell, Jaclyn E; Brelsfoard, Corey L (July 2023, Journal of Medical Entomology)

   Hillyer, Julian (Ed.)

   Abstract Microplastics (MPs) are common environmental pollutants; however, little is known about their effects after ingestion by insects. Here we fed Aedes (Stegomyia) aegypti (L.) and Aedes (Stegomyia) albopictus (Skuse) mosquito larvae 1 µm polystyrene MPs and examined the impacts of ingestion on adult emergence rates, gut damage, and fungal and bacterial microbiota. Results show that MPs accumulate in the larval guts, resulting in gut damage. However, little impact on adult emergence rates was observed. MPs are also found in adult guts postemergence from the pupal stage, and adults expel MPs in their frass after obtaining sugar meals. Moreover, MPs effects on insect microbiomes need to be better defined. To address this knowledge gap, we investigated the relationship between MP ingestion and the microbial communities in Ae. albopictus and Ae. aegypti. The microbiota composition was altered by the ingestion of increasing concentrations of MPs. Amplicon sequence variants (ASVs) that contributed to differences in the bacterial and fungal microbiota composition between MP treatments were from the genera Elizabethkingia and Aspergillus, respectively. Furthermore, a decrease in the alpha diversity of the fungal and bacterial microbiota was observed in treatments where larvae ingested MPs. These results highlight the potential for the bacterial and fungal constituents in the mosquito microbiome to respond differently to the ingestion of MPs. Based on our findings and the effects of MP ingestion on the mosquito host micro- and mycobiome, MP pollution could impact the vector competence of important mosquito-transmitted viruses and parasites that cause human and animal diseases. 

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3. Aedes aegypti gut transcriptomes respond differently to microbiome transplants from field‐caught or laboratory‐reared mosquitoes

   https://doi.org/10.1111/1462-2920.16576  

   Hegde, Shivanand; Brettell, Laura E; Quek, Shannon; Etebari, Kayvan; Saldaña, Miguel A; Asgari, Sassan; Coon, Kerri L; Heinz, Eva; Hughes, Grant L (February 2024, Environmental Microbiology)

   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. 

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4. Microbiota Composition Associates With Mosquito Productivity Outcomes in Belowground Larval Habitats

   https://doi.org/10.1111/mec.17614  

   Zhao, Serena Y; Sommer, Andrew J; Bartlett, Dan; Harbison, Justin E; Irwin, Patrick; Coon, Kerri L (January 2025, Molecular Ecology)

   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. 

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5. Predaceous Toxorhynchites mosquitoes require a living gut microbiota to develop

   https://doi.org/10.1098/rspb.2019.2705  

   Coon, Kerri L.; Valzania, Luca; Brown, Mark R.; Strand, Michael R. (January 2020, Proceedings of the Royal Society B: Biological Sciences)

   null (Ed.)

   Most species of mosquitoes are detritivores that feed on decaying plant and animal materials in their aquatic environment. Studies of several detritivorous mosquito species indicate that they host relatively low diversity communities of microbes that are acquired from the environment while feeding. Our recent results also indicate that detritivorous species normally require a living gut microbiota to grow beyond the first instar. Less well known is that some mosquitoes, including those belonging to the genus Toxorhynchites , are predators that feed on other species of mosquitoes and nektonic prey. In this study, we asked whether predaceous Toxorhynchites amboinensis larvae still require living microbes in their gut in order to develop. Using the detritivorous mosquito Aedes aegypti as prey, we found that T. amboinensis larvae harbour bacterial communities that are highly similar to that of their prey. Functional assays showed that T. amboinensis first instars provided axenic (i.e. bacteria-free) prey failed to develop, while two bacterial species present in gnotobiotic (i.e. colonized by one or more known bacterial species) prey successfully colonized the T. amboinensis gut and rescued development. Axenic T. amboinensis larvae also displayed defects in growth consistent with previously identified roles for microbe-mediated gut hypoxia in nutrient acquisition and assimilation in A. aegypti. Collectively, these results support a conserved role for gut microbes in regulating the development of mosquitoes with different feeding strategies. 

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