Soil bacterial diversity in the tropical dry deciduous forest of Ajodhya hills, Purulia, West Bengal

Introduction and objective

Ajodhya hill is one of the important regions of “Jungle Mahals”, a tropical dry deciduous forest with a huge number of water bodies located in Purulia, West Bengal. Soil signifies a composite ecosystem that includes a variety of microorganisms including bacteria. In this study, the bacterial diversity of soil samples from different sites of Ajodhya hill was estimated.

Materials and methods

Study sites include Ajodhya hilltop, Marble lake, Upper dam, Loharia lake, Thurga falls, and Vertical hill of Ajodhya. Soil samples from these regions were collected and different groups of bacterial populations were enumerated by colony forming unit (cfu). Physico-chemical parameters of soil samples were analysed.

Results and discussion

The population of aerobic heterotopic, starch hydrolyzing, phosphate solubilizing, lipid solubilizing, nitrate reducing, spore forming, Gram-negative, and nitrifying bacteria varied from 9.43 to 12.55 × 10⁶, 2.88 to 6.11 × 10³, 6.07 to 9.23 × 10³, 2.21 to 5.91 × 10²,3.23 to 9.7 × 10³, 6.81 to 12.30 × 10⁵, 2.22 to 8.6 × 10³, 2.7 to 8.63 × 10³ cfu/g of dry soil respectively.The organic carbon content ranged from 0.39% to 0.68% in the soil sample collected. The available nitrogen, potassium, phosphate, and pH levels in the soil sample ranged from 42.55 to 144.68 mg/kg, 1661.61 to 3749.28 mg/kg, 153.37 to 349.36 mg/kg, and 5.4 to 8. Results of one-way ANOVA indicated significant variation (p < 0.05) in the bacterial population of the soil sample among the various sites. Hierarchical clustering analysis between the various bacterial groups present in the soil helped with unraveling the similitudes connecting them. The Renyi diversity index helped with understanding the diversity, richness, and evenness of the microbial population of the soil samples.

Conclusion

The outcomes reveal the highest bacterial diversity in Vertical hill and the least diversity in Ajodhya hilltop. The highest value for the Berger-Parker index found on the Ajodhya hilltop shows that the dominant species represent the larger part of the entire bacterial population of the hill. This variation in the diversity of soil bacteria is due to different microhabitats present in that area from where soil samples were collected.