Bacterial microbiota of Aedes aegypti mosquito larvae is altered by intoxication with Bacillus thuringiensis israelensis

Abstract

BackgroundInsect microbiota is a dynamic microbial community that can actively participate in defense against pathogens. Bacillus thuringiensis (Bt) is a natural entomopathogen widely used as a bioinsecticide for pest control. Although Bt’s mode of action has been extensively studied, whether the presence of microbiota is mandatory for Bt to effectively kill the insect is still under debate. An association between a higher tolerance and a modified microbiota was already evidenced but a critical point remained to be solved: is the modified microbiota a cause or a consequence of a higher tolerance to Bt?MethodsIn this study we focused on the mosquito species Aedes aegypti, as no work has been performed on Diptera on this topic to date, and on B. thuringiensis israelensis (Bti), which is used worldwide for mosquito control. To avoid using antibiotics to cure bacterial microbiota, mosquito larvae were exposed to an hourly increasing dose of Bti during 25 hours to separate the most susceptible larvae dying quickly from more tolerant individuals, with longer survival.ResultsDenaturing gradient gel electrophoresis (DGGE) fingerprinting revealed that mosquito larval bacterial microbiota was strongly affected by Bti infection after only a few hours of exposure. Bacterial microbiota from the most tolerant larvae showed the lowest diversity but the highest inter-individual differences. The proportion of Bti in the host tissue was reduced in the most tolerant larvae as compared to the most susceptible ones, suggesting an active control of Bti infection by the host.ConclusionsHere we show that a modified microbiota is associated with a higher tolerance of mosquitoes to Bti, but that it is rather a consequence of Bti infection than the cause of the higher tolerance. This study paves the way to future investigations aiming at unraveling the role of host immunity, inter-species bacterial competition and kinetics of host colonization by Bti that could be at the basis of the phenotype observed in this study.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-2741-8) contains supplementary material, which is available to authorized users.

Natural Variation in Physicochemical Profiles and Bacterial Communities Associated with Aedes aegypti Breeding Sites and Larvae on Guadeloupe and French Guiana

“…We found that Pseudomonas was more abundant at breeding sites and larvae on Guadeloupe than in French Guiana, whereas Serratia was more abundant in water and larvae from French Guiana. Pseudomonas and Serratia are genera commonly found both larvae and adult mosquitoes [42,61,64,[84][85][86][87], suggesting that the territory-specific differences observed on relative abundance of these genera at the breeding sites may be reflected in the microbiota of the corresponding adults and shape their transmission potential for pathogens.…”

Who is eating fructose within the Aedes albopictus gut microbiota?

“…To assess differences in bacterial community composition, DGGE fingerprint was performed as previously described (Tetreau et al ., ). Profiles were confronted to the profiles of DNA quantification and DNA 13 C‐enrichment along the gradient in order to select two fractions representatives of labelled DNA (heavy‐DNA fractions) and two representatives of unlabelled DNA (light‐DNA fractions) for further analyses.…”

The Tripartite Interaction of Host Immunity–Bacillus thuringiensis Infection–Gut Microbiota

“…We found the LC50 dose of Bt infection could suppress the humoral immune response in the third instar larvae of Plutella xylostella [ 80 ]. Growing evidence suggests that Bt-induced immunity is a dose-dependent effect [ 88 , 89 , 90 , 91 ].…”