Antimicrobial properties of marine endophytic fungi extracted from selected Malaysian sea weeds / Norasyikin Razali

Marine organisms possess unique structural features as compared to terrestrial organisms. The secondary metabolites produced by marine endophytic fungi have been regarded as an important source contributes to the natural chemotherapeutic agents. Due to the emergence of antibiotics resistance by certain pathogenic bacteria, there is an urge to seek for new candidates for alternative drugs. In search for a new source of active metabolites, seaweeds have been studied for the past several years. In this study, five marine endophytic fungi isolated from four Malaysian brown seaweeds Cystoseira nudicaulis, Mesogloia vermiculata, Eucheuma denticulatum and Padina australis were investigated for the antimicrobial properties by using antibacterial assay and disc diffusion method. The endophytes were grown in two types of media, PDA and PDA with 3% artificial sea salt (PDA3%). Out of ten marine endophytic fungi extracts, eight extracts (CN PDA, CN PDA3%, MV PDA, MV PDA3%, EDl PDA, EDl PDA3%, ED2 PDA and PA7 PDA3%) exerted weak (growth inhibition <20%) to moderate (growth inhibition 2:37%) antibacterial activity against pathogenic bacteria B.subtilis, E.coli, P.aeruginosa, S.aureus, S.enterica and S.typhimurium. As for antifungal activity, eight extracts (CN PDA, CN PDA3%, MV PDA, MV PDA3%, EDl PDA, EDl PDA3%, ED2 PDA3%, PA7 PDA and PA7 PDA3%) exhibited zone inhibition in the range of 6.5±0.71 to 12.0±1.41 mm against pathogenic fungi A.niger, C.albicans and T.rubrum. Fungicidal activity of extracts CN and EDl (both from PDA3%) was observed at the minimal concentration tested (0.625 mg/ml). The antimicrobial activity strength of extracts CN, MY, EDl, ED2 and PA7 was influenced by certain factors such as chemical composition, salinity and concentration of extracts. Marine endophytic fungi extracts isolated from seaweeds of Cystoseira nudicaulis, Mesogloia vermiculata and Eucheuma denticulatum have a promising potential as an alternative source for antimicrobial drugs by inhibiting both of pathogenic bacteria and fungi growth. Further study should be carried out in order to have better understanding on their mechanism(s) of action and to identify the bioactive compounds which responsible for antimicrobial activities.