Screening of Endophytic Fungi for Antimicrobial Activity

Abstract

Endophytes are poorly investigated group of microorganisms, but they represent an abundant and dependable source of novel bioactive compounds with huge potential for exploitation in wide variety of medicine, agriculture and industrial areas (Vanden et al. 1991). The objective of this project was to determine the antibacterial, antifungal activity and preliminary phytochemical analysis of fungal culture extract from Xylaria species. In the present study endophytic fungi isolated from different host plants were characterized for their antimicrobial activity using various methods like Agar well diffusion method, Broth microdilution method (colorimetric) & microdilution (spectrophotometric method). The main purpose of this study was to evaluate these endophytic fungi for the production of bioactive compounds. Methanolic extracts of the culture filterate were checked for their antibacterial activity using four bacterial cultures Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus megaterium and a fungal culture Candida albicans. From the studies, it may be concluded that fungal culture extract XF-4 PDB, XF-2 MEB & XF-4 MEB (11-20mm) was more effective against Escherichia coli. Against Staphylococcus aureus XF-2 MEB (12-24.5mm) was effective. XF-4 MEB (13-25mm) has more pronounced effect against Bacillus megaterium. Against Pseudomonas aeruginosa fungal extracts XF-2 MEB, XF-4 PDB (10.5-23mm) were more effective. While on the other hand for Candida albicans XF-4 MEB (12.5-21.5mm) had pronounced effect as compared with fluconazole standard antibiotic.The spectrophotometric microdilution studies revealed that the fungal extracts XF-4 PDB & XF-4 MEB showed strong antimicrobial activity against Bacillus megaterium with MIC 6µg/ml each. However against Pseudomonas aeruginosa XF-2 MEB had MIC 2µg/ml. XF-2 PDB & XF-4 PDB were effective against Staphylococcus aureus with MIC 3µg/ml each. Also MIC of XF-4 MEB was 4µg/ml against Candida albicans and MIC of extracts XF-4 PDB, XF-2 MEB was 2µg/ml. The results of this study indicate that Xylaria species can be explored further for a possible source of useful antimicrobial agents against pathogenic microorganisms which include Gram positive, Gram negative, fungi & yeasts. In the present study phytochemical investigation revealed that oth fungal extracts (XF-2 & XF-4) contain phytoconstituents like alkaloids, steroids, flavonoids, amino acids and carbohydrates.