Date of Award

6-2010

Thesis Type

Masters

Document Type

Dissertation

Divisions

Faculty of Science

Department

Institute of Biological Sciences

Institution

Universiti Malaya

Abstract

This study reports the screening of selected fungi isolated from Dee and Barrientos Islands, Antarctica, for their antimicrobial activities using two methods: a) plug assay method and b) disk diffusion method. The plug assay was carried out as preliminary screening forbiological activity against bacteria: Bacillus subtilis, Staphylococcus aureus,Escherichia coli, pseudomonas aeruginosa, and yeast: Candida albicans. The results showed that 35% from species possessed antibacterial activity; and these included: Geomyces sp.50-1/S7, Unidentified 75-1/S1, Geomyces sp.12-1/S21, Penecillium sp.75-1/S10, Geomyces sp.3-1/S5, Geomyces sp.3-4/S5 and Geomyces sp.146/S5. Most of the strains exhibited antibacterial activity against Gram-positive bacteria S. aureus and B. subtilis and no activity detected against yeast. The disk diffusion assay was carried out to confirm the bioactivity of selected fungi against bacteria: Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus, and yeasts: Candida albicans, Saccharomyces cerevisiae and Schizosaccharomyces pombe. In disk diffusion assay, crude ethyl acetate extracts of five strains of Geomyces species namely, Geomyces sp.50-1/S7, Geomyces sp.12-1/S21, Geomyces sp.3-1/S5, Geomyces sp.3-4/S5 and Geomyces sp.146/S5, were selected for antimicrobial assay. The selection of these five strains was based on their good activity which they produced during the preliminary screening. These five strains were cultivated on Potato dextrose broth (PDB) under stationary phase for three different incubations periods 10, 15 and 21 days. The strains exhibited activity after 15 days incubation then, the activity decreased. The results showed that, no activity was detected against yeast and Geomyces sp.50-1/S7 and Geomyces sp.12-1/S21 was lost their activity and this may be due to inconvenient liquid growth medium. Minimum inhibitory concentration of the active extracts was carried out against; B. subtilis, S. aureus, B. cereus and P. aeruginosa and the values ranged between 6.25 mg ml-1- 25 mg ml-1. Minimum bactericidal concentration was determined after subculture on to Luria Agar media and the values ranged from12.5 mg ml1 to 25 mg ml-1.

Initial

khm

Additional Information

Dissertation (M.A.) – Faculty of Science, Universiti Malaya, 2010.

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