Screening of endophytic fungi Xylaria for antibacterial and antifungal activity

Abstract

The search for and exploitation of natural products and their properties has been the mainstay of biotechnology research. Natural product search and discovery from endophytes of medicinal plants represents a challenge to the scientist. All the available evidence, points to natural product discovery continuing strongly and accelerating as a consequence of new search strategies and innovative microbiology. Many new drugs with interesting structures and biological activities continue to be reported. Without such discoveries, there would be a significant therapeutic deficit in several important clinical areas. Endophytes are the plant-associated microorganisms that live within the living tissues of their host plants without causing any harm to them. Almost all groups of microorganisms have been found in endophytic association with plants may it be fungi, bacteria or actinomycetes. They stimulate the production of secondary metabolites with a diverse range of biological activities. They have been known to produce enormous variety of strange and wonderful secondary metabolites, some of which have profound biological activities that can be exploited for human health and welfare. Some of the endophytic microorganisms can produce the same secondary metabolites as that of the plant thus making them a promising source of novel compounds. During the present investigation, endophytic fungus Xylaria was isolated from different regions of Western Ghats of India from different host plants. The fungal metabolites were sub cultured, filtered and extracted using various methods and the extracts were tested for both antibacterial and antifungal activity. The highest activity was observed with XF-4 and XF-14. E.coli was susceptible to only 2 extracts were as S.aureus and P.aeruginosa were susceptible to almost all the extracts including intracellular. B.megaterium showed comparatively less susceptibility to all extracts except for XF-14 extracellular and C.albicans was found to be susceptible to all extracts. So out of 4 strains of Xylaria XF - 14 extra showed highest inhibitory effect against all test organisms followed by XF-15. Further purification of the compound can be carried out and the final compound so obtained can be useful in treatment of various diseases.