Metagenomic exploration of bacterial community shifts before, during, and after passage through earthworm Eutyphoeus waltoni.

Abstract

Understanding the transformation of soil microbial communities during their passage through the earthworm gut provides essential insights into soil health and ecosystem functioning. In this study, we employed 16S rRNA gene sequencing to investigate the bacterial community dynamics in the surrounding soil, gut, and casts of anecic earthworm Eutyphoeus waltoni, an important ecosystem engineer. This research aims to elucidate the microbial selection and transformation processes that occur as microorganisms pass through the earthworm’s alimentary canal. E. waltoni was selected for its significant role in organic matter decomposition and nutrient cycling within Indian soils. While species like Eisenia fetida and Lumbricus terrestris are well-studied, E. waltoni remains understudied despite its ecological importance. We observed notable shifts in microbial communities across the three microhabitats, primarily composed of Firmicutes, Proteobacteria, Actinobacteria, Bacteroidetes, and Acidobacteria. The gut environment selectively enriched Firmicutes, particularly Clostridioides, and reduced Proteobacteria. In the cast, microbial recovery was partial, with the presence of genera such as Azospira and Nitrospira, which are linked to nutrient turnover. These findings demonstrate that E. waltoni selectively restructures microbial assemblages, promoting taxa that enhance nutrient cycling and biogeochemical processes.