Functional and phylogenetic diversity of root-associated bacteria of Ajuga bracteosa in Kangra valley

Present study investigates the cultivable diversity of root-associated bacteria from a medicinal plant Ajuga bracteosa in the Kangra valley, in order to determine their plant growth promoting (PGP) and biotechnological potential. The plant was found to exhibit a positive rhizosphere effect of 1.3–1.5. A total of 123 morphologically different bacteria were isolated from the rhizospheric soil and roots of the plant. Medium composition was found to have significant effect on the composition of isolated bacterial populations. Majority of the rhizospheric soil isolates belonged to α- and γ-Proteobacteria, with Pseudomonas constituting the most dominant species. Endophytic bacterial community, on other hand, consisted almost exclusively of Firmicutes. Majority of the isolates showed PGP activity by producing siderophores and indole acetic acid. Several isolates were found to exhibit very high antioxidant activity in the culture medium. A significant proportion of isolates also demonstrated other ecologically important activities like phosphate solubilization, nitrogen fixation, and production of hydrolytic enzymes including amylase, protease, lipase, chitinase, cellulase, pectinase and phosphatase. Firmicutes were found to be metabolically the most versatile group and performed multiple enzyme activities. This is the first systematic study of culturable bacterial community from the rhizosphere of A. bracteosa, particularly in the Kangra valley region.