Abstract
Microbial communities associated to insect species are involved in essential biological functions such as host nutrition, reproduction and survivability. Main factors have been described as modulators of gut bacterial community, such as diet, habit, developmental stage and taxonomy of the host. The present work focuses on the complex changes that gut microbial communities go through when wild insects are introduced to artificial rearing conditions. Specifically, we analyzed the effect of the laboratory colonization on the richness and diversity of the gut bacteriome hosted by the fruit fly pest Anastrepha fraterculus sp. 1. Bacterial profiles were studied by amplicon sequencing of the 16S rRNA V3–V4 hypervariable region in gut samples of males and females, in teneral (1-day-old, unfed) and post-teneral (15-day-old, fed) flies. A total of 3,147,665 sequence reads were obtained and 32 bacterial operational taxonomic units (OTUs) were identified. Proteobacteria was the most abundant phylum (93.3% of the total reads) and, Wolbachia and Enterobacter were the most represented taxa at the genus level (29.9% and 27.7%, respectively, of the total read counts). Wild and laboratory flies showed highly significant differences in the relative abundances of bacteria. The analysis of the core bacteriome showed the presence of five OTUs in all samples grouped by origin, while nine and five OTUs were exclusively detected in laboratory and wild flies, respectively. Irrespective of fly origin or sex, a dominant presence of Wolbachia was observed in teneral flies, whereas Enterobacter was highly abundant in post-teneral individuals. We evidenced significant differences in bacterial richness and diversity among generations under laboratory colonization (F0, F1, F3 and F6) and compared to laboratory and wild flies, displaying also differential patterns between teneral and post-teneral flies. Laboratory and wild A. fraterculus sp. 1 harbor different gut bacterial communities. Laboratory colonization has an important effect on the microbiota, most likely associated to the combined effects of insect physiology and environmental conditions (e.g., diet and colony management).
Highlights
Insects can be considered as multiorganismal entities
After an ultimate and strict trimming process, a total of 3,147,665 high quality reads were achieved from a total of 66 A. fraterculus sp. 1 gut samples
We identified two operational taxonomic units (OTUs) (OTU22 assigned to Commensalibacter and OTU19, classified as an unknown member of the Saccharibacteria phylum) exclusively present in teneral wild flies from feijoa host fruit
Summary
Insects can be considered as multiorganismal entities. Their microbiota accounts for up to 10% of the insect’s biomass and is involved in essential physiological roles modulating host fitness (Zilber-Rosenberg and Rosenberg, 2008; Feldhaar, 2011; Douglas, 2015; Morris, 2018; Carthey et al, 2019; Brown et al, 2020). Insect gut microbiome comprises obligate and facultative symbionts, opportunistic parasites, and mutualistic microbes (Bourtzis and Miller, 2003; Pontes and Dale, 2006), a complex structure that is mainly affected by host environment and taxonomy (Colman et al, 2012; Engel and Moran, 2013; Augustinos et al, 2019). Gut bacteria are able to perform degradation of natural toxins such us phenolic compounds and complex terpenoids involved in plant defense (Hammer and Bowers, 2015; Berasategui et al, 2016; Jing et al, 2020) or chemical toxins facilitating host insecticide resistance (Vontas et al, 2011)
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