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Microbiota Plays a Role in Oral Immune Priming in Tribolium castaneum - PubMed

  • ️Fri Jan 01 2016

Microbiota Plays a Role in Oral Immune Priming in Tribolium castaneum

Momir Futo et al. Front Microbiol. 2016.

Abstract

Animals are inhabited by a diverse community of microorganisms. The relevance of such microbiota is increasingly being recognized across a broad spectrum of species, ranging from sponges to primates, revealing various beneficial roles that microbes can play. The red flour beetle Tribolium castaneum represents a well-established experimental model organism for studying questions in ecology and evolution, however, the relevance of its microbial community is still largely unknown. T. castaneum larvae orally exposed to bacterial components of the entomopathogen Bacillus thuringiensis bv. tenebrionis showed increased survival upon a subsequent challenge with spores of this bacterium. To investigate whether T. castaneum microbiota plays a role in this phenomenon, we established a protocol for raising microbe-free larvae and subsequently tested whether they differ in their ability to mount such a priming response. Here we demonstrate that larvae with significantly lowered microbial loads, show decreased survival upon secondary challenge with B. thuringiensis bv. tenebrionis spores, compared to animals that were allowed to regain their microbiota before priming. Although the exact mechanism of oral immune priming is unclear, we here suggest that microbiota plays a crucial role in oral immune priming in this species.

Keywords: Bacillus thuringiensis; Tribolium castaneum; immune priming; innate immunity; microbiota; oral infection.

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Figures

FIGURE 1
FIGURE 1

Bacterial load of larvae raised on “untreated,” “sterilized,” and “recolonized” flour treatments, expressed as a ΔCT value of the bacterial 16S rRNA gene relative to the T. castaneum reference gene, rp49. Experiment 1 is based on three samples (each containing ten pooled larvae) per flour treatment, while Experiment 2 is based on eight independently produced flour replicates per treatment. From each of those, three samples (of ten pooled larvae each) were analyzed and the respective mean ΔCT values are indicated by the dots. Boxplots show the overall median and quartiles, whiskers indicate standard errors. Statistically significant differences are indicated by the asterisks (p < 0.001).

FIGURE 2
FIGURE 2

Effect of microbiota on T. castaneum survival after oral immune priming and challenge for Experiments 1 and 2. Survival of larvae raised on the following flour treatments: “untreated”—(A,D), “sterilized”—(B,E), “recolonized”—(C,F). Priming treatments were primed with Btt spore culture supernatants (“Primed”), unconditioned spore culture medium (“Medium”) or phosphate-buffered saline (“PBS”) and subsequently challenged with Btt spores (“Challenged”) or PBS (“Control”). Sample sizes for each experimental group are shown in the treatment legends. Panels (D–F) (Experiment 2) show the cumulative data from 8 jar-replicates per flour treatment. Statistically significant differences are indicated by the asterisks (p ≤ 0.001).

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