Introducing an environmental microbiome to axenic Aedes aegypti mosquitoes documents bacterial responses to a blood meal

Abstract

ABSTRACT Axenic Aedes aegypti mosquitoes were colonized with bacteria from an environmental water source to compare the midgut microbiota acquired from the wild to the microbiome of insectary-reared mosquitoes, specifically over the course of blood meal digestion. 16S rRNA gene sequencing revealed that diversity, composition, and community turnover of the midgut microbiomes were distinct between the insectary and environmental groups, with the environmental microbiomes having a greater diversity and larger temporal shifts over the course of the blood meal. Metagenomic prediction from the 16S rRNA gene sequence data pointed to metabolic processes such as vitamin biosynthesis, fatty acid recycling, and fermentation pathways differentiating the functional potential of the two different microbiomes. To further test if we could identify functional traits that distinguished the two microbiomes, we performed a culture-based assay. Culturable bacteria were more abundant in the insectary microbiomes and there was very little overlap in the taxonomy of bacteria recovered from the insectary or environmental groups. The ability of the isolates to lyse blood cells was determined on blood agar plates, and only isolates from the environmental microbiome harbored the ability to perform hemolysis in culture. These data support that the differences in taxonomy observed between the two different microbiomes also result in differences in the functional potential of the community. Thus, this study demonstrates the power of the axenic mosquito model to shed light on the community ecology of the mosquito microbiome, and the potential to better represent the microbiomes of wild mosquitoes in a laboratory setting. IMPORTANCE The blood meal of the female mosquito serves as a nutrition source to support egg development, so is an important aspect of its biology. Yet, the roles the microbiome may play in blood digestion are poorly characterized. We employed axenic mosquitoes to investigate how the microbiome differs between mosquitoes reared in the insectary versus mosquitoes that acquire their microbiome from the environment. Environmental microbiomes were more diverse and showed larger temporal shifts over the course of blood digestion. Importantly, only bacteria from the environmental microbiome performed hemolysis in culture, pointing to functional differences between bacterial populations. These data highlight that taxonomic differences between the microbiomes of insectary-reared and wild mosquitoes are potentially also related to their functional ecology. Thus, axenic mosquitoes colonized with environmental bacteria offer a way to investigate the role of bacteria from the wild in mosquito processes such as blood digestion, under controlled laboratory conditions.