Modification of the soil bacterial metagenome during vermicomposting by Eisenia fetida

Annelida is a phylum comprising a large variety of segmented worms including earthworms. Earthworms are ecologically important, keystone species used extensively in the study of soil pollution and valuable models for understanding regeneration. Recently, our group and others have sequenced the complete genome of E. fetida, a widely distributed vermicomposting earthworm species. We have also studied dynamic changes in the earthworm transcriptome during regeneration. Here, we used a combination of conventional microbiology techniques, NGS based 16s rRNA sequencing, and PCR using species specific primers to comprehensively catalog the metagenome associated with E.fetida. We show that in the absence of earthworms, decomposition of vegetative matter results in a rapid rise in the microbial population while the presence of the earthworms leads to a less diverse microbial population. We speculate that the earthworm secretes yet unknown factors into the soil that selects for the microbial population and together accelerate decomposition. We identified the obligate and facultative symbiont microbial species that are embedded deep within the bodywall. Further, we show that the regenerating earthworm fails to restore the symbiotic microbial population completely.