Isolation and characterization of aerobic microorganisms with cellulolytic activity in the gut of endogeic earthworms

Resumen

The ability of earthworms to decompose lignocellulose involves the assistance of microorganisms in their digestive system. While many studies have revealed a diverse microbiota in the earthworm gut, including aerobic and anaerobicmicroorganisms, it remains unclear which of these species contribute to lignocellulose digestion. In this study, aerobicmicroorganisms with cellulolytic activity isolated from the gut of two endogeic earthworms, Amynthas heteropoda (Megascolecidae) and Eisenia fetida (Lumbricidae) were isolated by solid culture of gut homogenates using filter paper as acarbon source. A total of 48 strains, including four bacterial and four fungal genera, were isolated from two earthworm species. Characterization of these strains using enzyme assays showed that the most representative ones had exocellulase andxylanase activities, while some had weak laccase activity. These findings suggest that earthworms digest lignocellulose byexploiting microbial exocellulase and xylanase besides their own endocellulase. Phylogenetic analysis showed that among thecellulolytic isolates in both earthworm species Burkholderia and Chaetomium were the dominant bacterial and fungal members.[Int Microbiol 2012; 15(3):121-130]