Metagenomic Exploration of Bacterial Community Structure of Earthworms’ Gut

Abstract

Living organisms are naturally bestowed with unique and imitable qualities for maintaining ecological balance and earthworms are no exceptions. These so-called keystone species of terrestrial ecosystems are equipped with wonderful machinery, allowing them to nurture soil beautifully. Earthworm gut represents a potential microbial reservoir, having a complex interdependence with the host. The study aimed to profile bacterial community structure of three earthworm species belonging to two different life forms; Perionyx excavatus and Eudrilus eugeniae (epigeic), Polypheretima elongata (endogeic) respectively. Diversity analysis using 16S amplicon sequencing revealed that the dominant phyla were Proteobacteria (34.17-77.88) followed by Actinobacteria (13.43-35.54%), Firmicutes (1.69-15.45%) and Bacteroidetes (0.51-8.12%). The alpha diversity indices explicit similar gut microbiota of Perionyx excavatus and Eudrilus eugeniae and while higher alpha diversity was recorded in comparison to Polypheretima elongata gut. The taxonomic to the phenotypic annotation of 16S rRNA metagenomes revealed that dominance of Gram-negative bacterial community in all earthworm species while, Polypheretima elongata comprises higher percentage (78%) of Gram-negative bacterial community to Perionyx excavatus (32.3%) and Eudrilus eugeniae (38.3%). The oxygen requirement phenotypic analysis showed that all earthworm species were abundant with aerobic followed by anaerobic bacterial groups. Furthermore, functional metabolism phenotypic analysis revealed that a high abundance of ammonia oxidizers (29.3-80.2%), the gut microbiomes showed the relative abundance of sulphate reducer (22.6-78.7%), nitrite reducer (19.8-73.2%), dehalogenators (12.6-25.1%), illustrating in the role of these microbial communities in various degradation and bioremediation processes. The present study signifies the intrinsic gut microbiota of earthworm species for intensified biodegradation.