Isolation, Characterization and Practical Significance of Cellulose Degrading Bacteria from the Gut Wall of Two Ecologically Distinct Earthworms

Abstract

This study has determined the relationship of culturable community of cellulose degrading bacteria (CDB) within the gut walls of two habitat-specific earthworm species, epigeic (compost heap inhabitant) earthworm, Perionyx excavatus (PE) and an endogeic (submerged rice field inhabitant), Glyphidrilus spelaeotes (GS) and their functional significance. The 16Sr RNA analysis for the isolated CDB from two ecologically distinct earthworms clearly showed the presence of distinct communities of CDB in their gut ecosystem. Enzymatic assay of cellulase for the isolated CDB showed significantly higher cellulase activity compared to the reference strain M-23, Cellulomonas cellulans (P < 0.01, one-way ANOVA). The functional significance of such high cellulase activity was also demonstrated by the enhancement of decomposition of rice straw and fresh vegetation biomass in the presence of native microbiota community. The growth rate of CDB of epigeic PE was approximately twice slower than that of CDBs of endogeic GS. The CDB of PE exhibited 12 polymorphs of esterase isozyme as against 4 polymorphs for CDB of GS. The present study emphasizes the functionally significant relationship of gut wall CDB and host earthworm for sustaining efficient C-cycling in agroecosystems.