Characterization of the bacterial communities of casts from Eisenia andrei fed with different substrates

• We characterized the bacterial community of casts of earthworm Eisenia andrei.
• Cast from cow, pig and horse manure had the same α-diversity.
• Bacterial community composition depended on the manure fed by earthworms.
• Most abundant bacterial phyla were Proteobacteria, Firmicutes and Actinobacteria.

Earthworms play a key role during the first stage of decomposition by enhancing the activity of microorganisms. As organic matter passes throughout the earthworm gut, nutrient pools and microbial communities are modified and released in casts. Here we used 16S rRNA pyrosequencing and metagenomic analysis to characterize the bacterial communities of casts from the earthworm Eisenia andrei fed with different food sources (cow, horse and pig manure). We found that the bacterial communities of cast strongly depended on the food source ingested by earthworms; although, no differences in α-diversity were detected. Bacterial communities of casts were mainly comprised of a variable amount of OTUs (operational taxonomic unit) belonging to the phyla Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, with minor contributions from the phyla Verrucomicrobia, Chloroflexi, Hydrogenedentes, Latescibacteria, Planctomycetes and Candidatus Saccharibacteria. From these bacterial profiles we found OTUs that worked out as biomarkers for each bacterial community allowing us to discriminate among food sources.