Biology subjects

Cappelli, A.

Publications and source records attributed to Cappelli, A..

4 recordsLinked to original sources

bioRxiv2026

Microbiota-driven, strain-specific Asaia colonisation modulates mosquito vector competence

Microbiota-based mosquito control strategies are founded on the ability of bacterial symbionts to modify host biology and/or pathogen transmission. However, symbionts do not operate in isolation. Their colonisation, persistence and biological effects arise within a complex ecological network comprising the host and its resident microbiota. We hypothesized that colonisation success is not only an intrinsic property of a bacterial symbiont but emerges from interactions between bacterial strain, host background, and the native microbial community. To test this, we compared recolonisation by endogenous and exogenous Asaia strains in the invasive mosquito Aedes koreicus using wild-type and axenic mosquitoes to experimentally manipulate the microbial composition. We found that endogenous and exogenous strains followed distinct colonisation trajectories. Depletion of the resident microbiota selectively rescued colonisation by the endogenous strain, whereas both strains successfully disseminated to transmission-relevant tissues despite contrasting early gut dynamics. Furthermore, these strain-specific colonisation dynamics were associated with increased Semliki Forest virus (SFV) transmission and enhanced adult longevity, particularly following colonisation by the exogenous strain. Our findings indicate that resident microbial communities act as selective ecological filters that shape symbiont colonisation in a strain-dependent manner. More broadly, this study demonstrates that the biological effects of mosquito symbionts emerge from interactions between bacterial strains and the microbial community context, providing an ecological framework for the rational and effective development of microbiota-based vector control strategies.

microbiology↗

bioRxiv2025

Do heatwaves impact mosquitoes? Multi-level analyses across developmental stages in Aedes albopictus

The increase in the frequency and intensity of heatwaves (HWs) under global warming is expected to have more dramatic biological impacts on insects than mean temperature increases by challenging their thermal thresholds. However, experimental evidence that quantifies the impact of HWs on insects in their ecological context is limited. Here, we measured across multiple biological scales (e.g. fitness, physiology, transcriptomic and microbiota) the stage-specific responses of the arboviral vector Aedes albopictus when experiencing an ecologically relevant HW. In arboviral vectors, only females require a blood-meal thus contributing to the transmission cycle, but males, eggs and larvae can also be the target of control strategies to reduce population size. As such the understanding of the responses to a HW during mosquito development has both biological and epidemiological relevance. We observed stage-specific responses, starting at the egg stage. We saw egg hatching decreasing and delaying after HW exposure. On the contrary, larvae showed to be resilient to HW. Larvae repurposed their energy resulting in trivial mortality, but delayed development. At the adult stage, we observed a marked sex difference, with extensive (>50%) male mortality, accompanied by a small (16) number of genes elicited following HW exposure, which indicates that males have limited coping mechanisms against hot events. In females, we observed a reduced reproductive output, but only when HW occurred after a blood-meal. Finally, we saw extensive HW-dependent changes in the microbial composition of larvae, but female microbiota remained dominated by Wolbachia regardless of the thermal challenge. Our results have relevant implications for both the understanding of mosquito biology and the implementation of vector control strategies as the climate crisis progresses.

ecology↗

bioRxiv2023

De-novo genome assembly of the invasive mosquito species Aedes japonicus and Aedes koreicus

Recently, two invasive Aedes mosquito species, Ae. japonicus and Ae. koreicus, are circulating in several European countries posing potential health risks to humans and animals. Vector control is the main option to prevent mosquito-borne diseases, and an accurate genome sequence of these mosquitoes is essential to better understand their biology and to develop effective control strategies. Here, we present a de novo genome assembly of the Ae. japonicus (Ajap1) and Ae. koreicus (Akor1) based on a hybrid approach that combines Oxford Nanopore long reads and Illumina short reads data. Their quality was ascertained using various metrics. Masking of repetitive elements, gene prediction and functional annotation was performed. Sequence analysis revealed a very high presence of repetitive DNA and, among others, thermal adaptation genes and insecticide-resistance genes. The RNA sequencing analysis of larvae and adults of Ae. koreicus and Ae. japonicus exposed to different temperatures revealed genes showing a thermal-dependent activation. The assembly of Akor1 and Ajap1 genomes constitutes the first updated collective knowledge of the genomes of both mosquito species, providing the possibility to understand key mechanisms of their biology such as the ability to adapt to harsh climates and to develop insecticide-resistance mechanisms.

genomics↗

bioRxiv2020

Phylogenomics reveals that Asaia symbionts from insects underwent convergent genome reduction, preserving an insecticide-degrading gene

The mosquito microbiota is composed by several lineages of microorganisms whose ecological roles and evolutionary histories have yet to be investigated in depth. Among these microorganisms, Asaia bacteria play a prominent role, given its abundance in the gut, reproductive organs and salivary glands of different mosquito species, while its presence has also been reported in several other insects. Notably, Asaia has great potential as a tool for the control of mosquito-borne diseases. Here, we present a wide phylogenomic analysis of Asaia strains isolated from different species of mosquito vectors and from different populations of the Mediterranean fruit fly (medfly) Ceratitis capitata, an insect pest of worldwide economic importance. We show that phylogenetically distant lineages of Asaia experienced independent genome reductions, despite following a common pattern, characterized by the early loss of genes involved in genome stability. This result highlights the role of specific metabolic pathways in the symbiotic relationship between Asaia and the insect host. Finally, we discovered that all but one of the Asaia strains included in the study possess the pyrethroid hydrolase gene. Phylogenetic analysis revealed that this gene is ancestral in Asaia, strongly suggesting that it played a role in the establishment of the symbiotic association between these bacteria and the mosquito hosts. We propose that this gene from the symbiont contributed to initial pyrethroid resistance in insects harboring Asaia, also considering the widespread production of pyrethrins by several plants. ImportanceWe have studied genome reduction within several strains of the insect symbiont Asaia, isolated from different species/strains of mosquito and medfly. Phylogenetically distant strains of Asaia, despite following a common pattern involving the loss of genes related to genome stability, have undergone independent genome reductions, highlighting the peculiar role of specific metabolic pathways in the symbiotic relationship between Asaia and its host. We also show that the pyrethroid hydrolase gene is present in all the Asaia strains isolated except for the South American malaria vector An. darlingi, for which resistance to pyrethroids has never been reported, suggesting a possible involvement of Asaia in determining the resistance to insecticides.

microbiology↗