Isolation of fungal endophytes from Garcinia mangostana and their antibacterial activity

Abstract

The objective of this study is to screen the antibacterial activity of endophytic fungi isolated from surface sterilized leaves and small branches of Garcinia mangostana plant found in Indonesia. The crude extracts of ethyl acetate (EtOAc) of the 24 fermentation broths from 24 endophytic fungi were tested for their antibacterial activity against Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Salmonella typhi ATCC 14028 and Micrococcus luteus (ATCC 10240), by the agar diffusion method. The result showed that 10 of the 24 isolates (41.6%) exhibited antibacterial activity against at least one pathogenic microorganism. Isolate RGM-02 displayed the strongest antibacterial activity against gram-positive bacteria. The minimum inhibitory concentration (MIC) of the crude ethyl acetate extracts of isolate RGM-02, inhibited S. aureus (MIC 25 μg/ml), B. subtilis (MIC 50 μg/ml), M. luteus (MIC 25 μg/ml), E. coli (MIC 200 μg/ml), S. typhi (MIC 200 μg/ml) and P. aeruginosa (MIC 100 μg/ml), respectively. The molecular identification revealed that the isolate RGM-02 represented Microdiplodia hawaiiensis CZ315. This study shows that endophytes of ethno medicinal plants could be a good source of antibacterial substances.

Keywords: Endophytic fungi, antibacterial agents, Garcinia mangostana, molecular identification