Nocardiopsis sp. 5 Endophytic to Tulsi Leaves – Isolation and Antimicrobial Activity

Abstract

Aims: To isolate and identify the endophytic Nocardiopsis sp.5 from Tulsi (Ocimum sanctum) leaves and estimates its antimicrobial activity against various human pathogens and tea pathogens. Study Design: Rare endophytic actinobacteria isolation, identification and estimation of antimicrobial activity. Place and Duration of Study: Department of Botany and Department of Bioinformatics, Nirmala College for Women, Coimbatore – between December 2011 and December 2012. Methodology: Pre-sterilization of Ocimum sanctum leaves and isolation of rare endophytic actinomycetes using selective media. Estimation of antimicrobial activity of these isolates by primary and secondary streaking methods. Morphological and Molecular Identification of the most bioactive isolate. Results: Out of 11 endophytes, four isolates (2, 3, 5, and 9) showed antagonistic activity against tea and human pathogens. Among these four isolates, isolate no.5 showed maximum activity against all the human pathogenic microorganisms such as Staphylococcus aureus (21mm), Candida albicans (18 mm), Enterococcus faecalis (19mm), Vibrio cholera (18mm) and tea pathogens such as Glomerella cingulata (14mm) Hypoxylon serpens (17mm) and Pestalopsis theae (18mm). Hence, morphological and phylogenetic studies show that isolate no.5 belongs to Nocardiopsis group, showing 99% similarity to both Nocardiopsis synnemataformans and Nocardiopsis dassonvillei. Conclusion: Endophytic Nocardiopsis strain 5 was shown to produce good antimicrobial activity against plant pathogens and human pathogens. Further purification, structure elucidation and characterization of the antimicrobial compound from Nocardiopsis 5 strain are recommended. There is definite scope for bioprospecting of antagonistic actinomycetes from Western Ghats once appropriate consistent studies are undertaken.