AUTHOR=Chang Xiao , Xue Shuang , Li Ruimin , Zhang Yuanchen 

TITLE=Episyrphus balteatus symbiont variation across developmental stages, living states, two sexes, and potential horizontal transmission from prey or environment

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1308393

DOI=10.3389/fmicb.2023.1308393

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p><italic>Episyrphus balteatus</italic> is one representative Syrphidae insect which can provide extensive pollination and pest control services. To date, the symbiont composition and potential acquisition approaches in Syrphidae remain unclear.</p></sec><sec><title>Methods</title><p>Herein, we investigated microbiota dynamics across developmental stages, different living states, and two sexes in <italic>E. balteatus</italic> via full-length 16S rRNA genes sequencing, followed by an attempt to explore the possibility of symbiont transmission from prey <italic>Megoura crassicauda</italic> to the hoverfly.</p></sec><sec><title>Results</title><p>Overall, Proteobacteria and Firmicutes were the dominant bacteria phyla with fluctuating relative abundances across the life stage. <italic>Cosenzaea myxofaciens</italic> is dominant in adulthood, while <italic>Enterococcus silesiacus</italic> and <italic>Morganella morganii</italic> dominate in larvae and pupae of <italic>E. balteatus</italic>, respectively. Unexpectedly, <italic>Serratia symbiotica</italic>, one facultative endosymbiont commonly harbored in aphids, was one of the predominant bacteria in larvae of <italic>E. balteatus</italic>, just behind <italic>Enterococcus silesiacus</italic>. In addition, <italic>S. symbiotica</italic> was also surprisingly most dominated in <italic>M. crassicauda</italic> aphids (92.1% relative abundance), which are significantly higher than <italic>Buchnera aphidicola</italic> (4.7% relative abundance), the primary obligate symbiont of most aphid species. Approximately 25% mortality was observed among newly emerged adults, of which microbiota was also disordered, similar to normally dying individuals. Sexually biased symbionts and 41 bacteria species with pairwise co-occurrence in <italic>E. balteatus</italic> and 23 biomarker species for each group were identified eventually. Functional prediction showed symbionts of hoverflies and aphids, both mainly focusing on metabolic pathways. In brief, we comprehensively explored the microbiome in one Syrphidae hoverfly using <italic>E. balteatus</italic> reared indoors on <italic>M. morganii</italic> as the model, revealed its dominated symbiont species, identified sexually biased symbionts, and found an aphid facultative endosymbiont inhabited in the hoverfly. We also found that the dominated symbiotic bacteria in <italic>M. crassicauda</italic> are <italic>S. symbiotica</italic> other than <italic>Buchnera aphidicola</italic>.</p></sec><sec><title>Discussion</title><p>Taken together, this study provides new valuable resources about symbionts in hoverflies and prey aphids jointly, which will benefit further exploring the potential roles of microbiota in <italic>E. balteatus</italic>.</p></sec>