The digestive and defensive basis of carcass utilization by the burying beetle and its microbiota. Carcass transcriptome

Insects that use ephemeral resources must rapidly digest nutrients and simultaneously protect them from competitors. Here we used burying beetles (Nicrophorus vespilloides), which feed their offspring on vertebrate carrion, to investigate the digestive and defensive basis of carrion utilization. We characterized gene expression and the composition of the microbiota in the gut, anal secretions, and on carcasses used by the beetles. We found a strict functional compartmentalization of the gut involving the differential expression of immune effectors (antimicrobial peptides and lysozymes), as well as digestive and detoxifying enzymes. Furthermore, a consistent and unusual microbial community composed of Firmicutes, Proteobacteria, and a clade of ascomycetous yeasts (genus Yarrowia) was present in larval and adult guts, and was transmitted to the carcass via anal secretions, where the yeasts express extracellular digestive enzymes and produce antimicrobial compounds. Our results therefore reveal metabolic cooperation between the host and its microbiota for digestion, detoxification, and defense, which extends from the beetle’s gut to its nutritional resource.