Relative contributions of various endogenous and exogenous factors to the mosquito microbiota

Abstract

Background: The commensal microbiota of mosquitoes impacts their development, immunity, and competency, and could provide a target for alternative entomological control approaches. However, despite the importance of the mosquito/microbiota interactions, little is known about the relative contribution of endogenous and exogenous factors in shaping the bacterial communities of mosquitoes.

Methods: We used a high-throughput sequencing-based assay to characterize the bacterial composition and diversity of 665 individual field-caught mosquitoes, as well as their species, genotype at an insecticide resistance locus, blood-meal composition, and the eukaryotic parasites and viruses they carry. We then used these data to rigorously estimate the individual effect of each parameter on the bacterial diversity as well as the relative contribution of each parameter to the microbial composition.

Results: Overall, multivariate analyses did not reveal any significant contribution of the mosquito species, insecticide resistance, or blood meal to the bacterial composition of the mosquitoes surveyed, and infection with parasites and viruses only contributed very marginally. The main driver of the bacterial diversity was the location at which each mosquito was collected, which explained roughly 20% of the variance observed.

Conclusions: This analysis shows that when confounding factors are taken into account, the site at which the mosquitoes are collected is the main driver of the bacterial diversity of wild-caught mosquitoes, although further studies will be needed to determine which specific components of the local environment affect bacterial composition.

Keywords: Anopheles; Bacterial composition; Entomological control; High-throughput screening; Microbiome.

Fig. 1

Average relative abundance of bacterial phyla from each mosquito collection site in Guinea and Mali. Bacterial species from the Proteobacteria phylum are the most abundant, followed by Firmicutes and Actinobacteria. Less than 1% abund. represents the aggregate of all phyla that make up < 1% of all bacteria

Fig. 2

Principal coordinates analysis plot showing the dissimilarity between the microbial composition of individual mosquitoes based on the Bray-Curtis dissimilarity metric for sites in Guinea and Mali (a) and Guinea only (b). Each dot represents the bacterial composition of a single mosquito. The numbers in brackets near the axes indicate the proportion of the variance explained by the principal components 1 and 2 (PC1, PC2, respectively)

Fig. 3

Mosquito species diversity across collection sites in Guinea and Mali. Hybrid* represents samples identified as heterozygous for Anopheles gambiae and An. coluzzii at the S200X6.1 locus. Numbers above each bar represent the total number of mosquitoes with successfully characterized species from each site

Fig. 4

Distribution of mosquito knockdown resistance west (kdr-w [L1014F mutation variant]) in mosquitoes collected across Guinea and Mali. Numbers above each bar represent the total number of mosquitoes successfully genotyped at the kdr-w genotype, per site. RR Homozygous resistant, SS homozygous sensitive, R/S heterozygous

Figure 5

Host blood-meal composition of individual mosquitoes collected from Kankan using pyrethrum spray catches (a), Kankan using human landing catches (b), Kissidougou (c), Dabola (d), Faranah (e), Boffa (f), Mali (g). Each bar represents an individual mosquito