Antibacterial Activity of Endophytic Fungi Isolated from Medicinal Plants: Ocimum Gratissimum and Jatropha Tanjorensis.

Abstract:

Endophytes are gaining worldwide recognition because of their potential use in biotechnology and as sources of novel bioactive compounds. A total of 27 fungal endophytes were isolated from the root, stem and leaves of two medicinal plants; Ocimum gratissimum (13) and Jatropha tanjorensis (14). Occurrence of endophyte species of the plants were Alternaria alternata and Aspergillus flavus (22.22% each), Nigrosa oryzae and Penicillium chryseogenum (14.81% each) and Penicillium oxalicum (11.11%). Cladosporium sphaerospernum (7.41%) was isolated from Ocimum gratissimum only and Rhizoctonia solani (7.41%) from Jatropha tanjorensis only. More endophytes were present in the roots and leaves than stems of the plants. Antibacterial screening of 10mg/ml of fungal extracts on five test organisms (Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae), using the Agar Well Diffusion Method showed Alternaria alternata with inhibitory zones 20.5 ± 0.15mm – 32.7 ± 0.58mm; Penicillium chryseogenum (14.5 ± 0.20mm – 28.79± 0.26mm); Aspergillus flavus (18.7 ± 0.10mm – 24.7 ± 0.10mm) and Nigrosa oryzae (18.6 ± 0.15mm – 24.7 ± 0.06mm each), with their highest antibacterial activity on Staphylococcus aureus. Cladosporium sphaerospernum (20.9 ± 0.20mm – 30.0 ± 0.06mm) and Penicillium oxalicum (11.3 ± 0.01mm – 22.8 ± 0.15mm) were most inhibitory to Bacillus cereus. Rhizoctonia solani had the least zones of inhibition (8.20 ± 0.20mm – 14.7 ± 0.06mm) and most inhibitory to E. coli and Pseudomonas aeruginosa. The antibacterial activities of the extracts were comparable to that of the standard drug, chloramphenicol (28.4 ± 0.40mm – 36.0 ± 0.12mm). With further research and standardization, these extracts could serve as alternatives to synthesized antibiotics. Keywords: Antibacterial activity, endophytic fungi, Jatropha tanjorensis, Ocimum gratissimum