Antimicrobial And Antibiofilm Activities Of An Endophytic Fungus Lasiodiplodia Pseudotheobromae Ibrl Os-64 Isolated From Ocimum Sanctum L. Leaves
| dc.contributor.author | Mohd Taufiq Mat Jalil | |
| dc.date.accessioned | 2021-01-18T06:35:00Z | |
| dc.date.available | 2021-01-18T06:35:00Z | |
| dc.date.issued | 2019-08 | |
| dc.description.abstract | Endophytic fungi isolated from medicinal plants have been reported to possess antioxidant and antimicrobial activities. This study was aimed to verify the therapeutic values of the endophytic fungal isolated from a medicinal herb, Ocimum sanctum leaves against various pathogenic microorganisms. A total of 148 fungal isolates were obtained from different leaf maturity stages, including 19 from young, 33 from mature, 59 from old and 37 from senescent leaves. Overall, 134 out of 148 fungal isolates demonstrated significant inhibitory effect towards at least one tested microorganisms. There are several isolates exhibited antagonistic and volatile antimicrobial activity against the tested yeasts (Candida albicans IBRL; Candida utilis IBRL) and dermatophytic fungi such as Trichophyton rubrum IBRL SA1 and Microsporum fulvum IBRL SD3. However, one isolate IBRL OS-64 was selected based on its prominent activity on primary and secondary screenings. The isolate was identified as Lasiodiplodia pseudotheobromae based on micro-morphology, micro-morphology as well as molecular identification and named as L. pseudotheobromae IBRL OS-64. Improvement of cultural conditions including pre-culture age, addition of host plant, number of plug and agitation speed had significantly increased antibacterial activity of the fungal isolate with 57.6% of increment. The crude ethyl acetate extract of L. pseudotheobromae IBRL OS-64 showed a potent antibacterial activity against several test bacteria with the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values ranged from 62.5 to 500 μg/mL and 125 to 2000 μg/mL, respectively. The antibacterial activity of this isolate was concentration-dependent towards MRSA ATCC 33591, Streptococcus mutans and Yersinia enterocolitica based on time-kill curve study. The tested microbes that were exposed to ethyl acetate crude extract of L. pseudotheobromae IBRL OS-64 demonstrated degeneration and alteration of the cells which mainly attributed by disruption of cell membrane permeability and cell wall synthesis, based on scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. On bio-assay guided separation of extract, 1,2-benzenedicarboxylic acid, mono [2-ethylhexyl] ester, was the major compound and together with other several compounds may contribute to the antimicrobial activity of the fraction. The fungal extract showed low antioxidant activity and total phenolic content with the value of 208.1 μg/mL and 13.27 μg GAE/mg extract, respectively. On toxicity assay, the crude and partially purified fraction F5 demonstrated low-toxicity, and non-toxicity towards brine shrimp, respectively. The crude ethyl acetate extract of L. pseudotheobromae IBRL OS-64 exhibited significant anti-biofilm activity towards initial and pre-formed biofilm of MRSA ATCC 33591, S. mutans and Y. enterocolitica. For anti-biofilm activity, the extract demonstrated significantly higher anti-biofilm activity in initial biofilm formation as compared to pre-formed biofilm for all test bacteria. The extract showed inhibition percentage of 89.23 ± 0.8% and 54.14 ± 2.0% on the initial and pre-formed biofilm of S. mutans, respectively whereas for MRSA ATCC 33591, the inhibition percentage was 80.82 ± 1.2% and 61.39 ± 1.4% on the initial and pre-formed biofilm, respectively. Besides that, the fungal extract exhibited inhibition percentage with the value of 69.12 ± 1.4 % and 58.70 ± 1.1% for initial and pre-formed biofilm of Y. enterocolitica. Based on light microscopy (LM) and scanning electron microscopy (SEM) observations, the biofilms and microcolonies formed by test bacteria was badly destroyed by the extract. The microcolonies were greatly inhibited and diminished in the initial biofilm whilst most of extracellular polymeric substances (EPS) layer were slightly eradicated in pre-formed biofilm upon exposure to the fungal extract. Therefore, fraction F5 of ethyl acetate extract of L. pseudotheobromae IBRL OS-64 could be a potential and great candidate for antibacterial and anti-biofilm agent due to its significant activity and low toxicity. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/10884 | |
| dc.language.iso | en | en_US |
| dc.publisher | Universiti Sains Malaysia | en_US |
| dc.subject | Geographical | en_US |
| dc.title | Antimicrobial And Antibiofilm Activities Of An Endophytic Fungus Lasiodiplodia Pseudotheobromae Ibrl Os-64 Isolated From Ocimum Sanctum L. Leaves | en_US |
| dc.type | Thesis | en_US |
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