Bacillus licheniformis strain UKCH17 from northwestern Indian Himalayas: Characterization of chitinolytic enzyme and determination of its antifungal potential

Abstract

Bacterial biocontrol agents are viable alternatives to chemical pesticides with target specificity and ecological safety. Here, we have identified a pesticidal microbial agent, an extra cellular chitinase producing Bacillus strain (designated as UKCH17) from Uttarakhand soils, a biologically rich Northwestern Indian Himalayas ecosystem. The 16S rRNA gene sequence of UKCH17 showed 99% similarity with sequences of B. licheniformis available in the public domain. The culture supernatants have a maximum chitinase activity of 99 U/mL after 4 days of culturing. The isolate showed strong antifungal activity manifested in the form of progressive mycelia degradation of Rhizoctonia solani, Fusarium solani and Sclerotium rolfsi in dual culture plates. Mycelial deformities like constrictions and protoplast leakage were observed in microscopic studies. However, it showed little growth reduction in Helicoverpa armigera when fed on surface contaminated diet. The electrophoretic analysis showed a monomeric 70 kDa active enzyme having an optimum pH and temperature of 5 and 50ºC, respectively. The enzyme also obeyed Michaelis-Menten kinetics, the Km and kcat values being 0.387 mg colloidal chitin/mL and 6335 s-1, respectively. Partial characterization of chitinase gene also confirms the family 18 status of glycosyl hydrolase from UKCH17. Above all, seed bacterization improved germination percentage and other plant growth characteristics of Pisum sativum in sick pots of R. solani and S. rolfsi suggesting its utilization as potent antifungal biocontrol agent.