Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The susceptibility of Anopheles mosquitoes to Plasmodium infections relies on complex interactions between the insect vector and the malaria parasite. A number of studies have shown that the mosquito innate immune responses play an important role in controlling the malaria infection and that the strength of parasite clearance is under genetic control, but little is known about the influence of environmental factors on the transmission success. We present here evidence that the composition of the vector gut microbiota is one of the major components that determine the outcome of mosquito infections. A. gambiae mosquitoes collected in natural breeding sites from Cameroon were experimentally challenged with a wild P. falciparum isolate, and their gut bacterial content was submitted for pyrosequencing analysis. The meta-taxogenomic approach revealed a broader richness of the midgut bacterial flora than previously described. Unexpectedly, the majority of bacterial species were found in only a small proportion of mosquitoes, and only 20 genera were shared by 80% of individuals. We show that observed differences in gut bacterial flora of adult mosquitoes is a result of breeding in distinct sites, suggesting that the native aquatic source where larvae were grown determines the composition of the midgut microbiota. Importantly, the abundance of Enterobacteriaceae in the mosquito midgut correlates significantly with the Plasmodium infection status. This striking relationship highlights the role of natural gut environment in parasite transmission. Deciphering microbe-pathogen interactions offers new perspectives to control disease transmission.
ISSN: 1553-7366

hal-01546176
https://hal.archives-ouvertes.fr/hal-01546176
DOI : 10.1371/journal.ppat.1002742

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
During their immature life stages, malaria mosquitoes are exposed to a wide array of microbes and contaminants from the aquatic habitats. Although prior studies have suggested that environmental exposure shapes the microbial community structure in the adult mosquito, most reports have focused on laboratory-based experiments and on a single mosquito epithelium, the gut. In this study, we investigated the influence of the breeding site on the development of the Anopheles coluzzii and Anopheles gambiae microbiota in natural conditions. We characterized bacterial communities from aquatic habitats, at surface microlayer and subsurface water levels, to freshly emerge adult mosquitoes using multiplexed 16S rRNA gene pyrosequencing and we separately analyzed the microbiota associated with the different epithelia of adult individual, midguts, ovaries and salivary glands. We found that the distribution of bacterial communities in the aquatic habitats differed according to the depth of water collections. Inter-individual variation of bacterial composition was large in larvae guts but adult mosquitoes from a same breeding site shared quite similar microbiota. Although some differences in bacterial abundances were highlighted between the different epithelia of freshly emerged An. coluzzii and An. gambiae, an intriguing feature from our study is the particular similarity of the overall bacterial communities. Our results call for further investigations on the bacterial population dynamics in the different tissues to determine the distinctive characteristics of each microbiota during the mosquito lifespan and to identify specific interactions between certain key phyla or species and the insect life history traits.
ISSN: 1567-1348

hal-01546167
https://hal.archives-ouvertes.fr/hal-01546167
DOI : 10.1016/j.meegid.2014.09.029

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The development of Plasmodium falciparum within the Anopheles gambiae mosquito relies on complex vector-parasite interactions, however the resident midgut microbiota also plays an important role in mediating parasite infection. In natural conditions, the mosquito microbial flora is diverse, composed of commensal and symbiotic bacteria. We report here the isolation of culturable midgut bacteria from mosquitoes collected in the field in Cameroon and their identification based on the 16S rRNA gene sequencing. We next measured the effect of selected natural bacterial isolates on Plasmodium falciparum infection prevalence and intensity over multiple infectious feedings and found that the bacteria significantly reduced the prevalence and intensity of infection. These results contrast with our previous study where the abundance of Enterobacteriaceae positively correlated with P. falciparum infection (Boissiere et al. 2012). The oral infection of bacteria probably led to the disruption of the gut homeostasis and activated immune responses, and this pinpoints the importance of studying microbe-parasite interactions in natural conditions. Our results indicate that the effect of bacterial exposure on P. falciparum infection varies with factors from the parasite and the human host and calls for deeper dissection of these parameters for accurate interpretation of bacterial exposure results in laboratory settings.
ISSN: 1932-6203

hal-01546172
https://hal.archives-ouvertes.fr/hal-01546172
DOI : 10.1371/journal.pone.0081663