Diversity of Culturable Bacterial Microbiota of the Eisenia foetida Digestive Tract

The objective of this research was to isolate and identify biochemical and molecularly the culturable bacterial microbiota of the digestive tract of Eisenia foetida. Earthworms came from The Instituto de Reconversión Productiva y Bioenergética (IRBIO) and The Colegio de Postgraduados (COLPOS), México. The bacterial isolation took place on plates of Brain Heart Infusion (BHI) culture medium. There were obtained 56 (IRBIO) and 44 (COLPOS) bacterial isolates. The population consisted of 44-Gram negative and 56-Gram positive isolates. Over 50% of the bacterial isolates were rod-shaped cells. The 16S rRNA gene was sequenced and nine genera were identified in worms of IRBIO (Bacillus, Paenibacillus, Solibacillus, Staphylococcus, Arthrobacter, Pantoea, Stenotrophomonas, Acinetobacter y Aeromonas) and six in worms of COLPOS (Bacillus, Paenibacillus, Stenotrophomonas, Staphylococcus, Acinetobacter and Aeromonas). Bacillus was the predominant genus, with eight and six species in the oligochaetes from IRBIO and COLPOS, respectively. The most represented bacteria in the worms of both sites were Bacillus sp. and Bacillus subtilis. Probably, the predominance of Bacillus was due to the spore formation, a reproductive strategy that ensures their survival and spread in soil and oligochaetes digestive tract. The gut of E. foetida not only harbored bacterial species of agronomic importance, but also potentially pathogenic for humans (Staphylococcus warneri, Pantoea agglomerans and Stentrophomonas sp.). The highest bacterial diversity in worms from IRBIO could be due to their feeding on cattle manure, which is a rich source of bacteria.