Comparative Study on Bacterial Population Dynamics of Foregut, Midgut, and Hindgut Content of Perionyx excavatus (Perrier) Isolated from Eco-friendly, Non-hazardous Vermicompost.

Abstract

The ideal condition of earthworm gut promotes growth and multiplication of beneficial soil microorganisms eliminating pathogens and converts organic wastes into nutrients rich compost. The present study has been carried out to determine the population dynamics of earthworm gut bacteria and to find out relative abundance of different functional bacterial groups in the foregut, midgut, and hindgut of earthworm Perionyx excavatus. To assess bacterial diversity, a viable plate count method was adopted. In the different gut region of earthworm, aerobic heterotrophic, amylolytic, Bacillus, Gram-negative, proteolytic, fat hydrolyzing, nitrate-reducing, nitrifying, asymbiotic nitrogen-fixing, Azotobacter, and phosphate solubilizing bacterial populations ranged from 22.2 to 241.6 × 106, 8.0 to 171.60 × 106, 1.83 to 2.79 × 106, 10.68 to 23.04 × 104, 3.70 to 5.52 × 104, 59.60 to 208.40 × 104, 1.86 to 7.34 × 104, 10.94 to 19.78 × 104, 0.80 to 3.42 × 104, 7.83 to 13.70 × 104, 1.31 to 2.67 × 104cfu/ml gut suspension, respectively. The results of the one-way ANOVA revealed that the bacterial load of most of the bacterial groups was significantly higher (p < 0.05) in the hindgut region, followed by midgut and foregut. Only the density of the proteolytic group was significantly higher (p < 0.05) in the midgut region followed by foregut and hindgut. Starch hydrolyzing bacteria constitute the largest group of bacteria in the gut content. From principal component analysis, two components were extracted with the eigenvalues of 8.485 and 1.132. Agglomerative hierarchical cluster analysis revealed that the bacterial populations were clustered into four different groups. Quantitative variation among bacterial groups in earthworm's gut seems to determine the soil health and composting efficiency; from this point of view, the present study will provide a better understanding about different functional bacterial groups of earthworm's guts and might be helpful in sustainable agriculture and waste management.