An Investigation on Antibacterial and Antifungal Activities of Actinomycetes Associated with 17 Medicinal Plants Collected in Northern Vietnam
Main Article Content
Abstract
Actinomycetes associated with plants are those that live on the surface, inside, or outside the plants, and have a reciprocal relationship with the plants. These actinomycetes have recently been found to possess many beneficial activities. The Northwest region of Vietnam is home to various valuable medicinal plants, of which the health-healing compounds, the microorganisms, particularly actinomycetes, are a promising research subject. In this study, we screened 136 endophytic and surface-associated actinomycetous strains isolated from 17 medicinal plants collected in the Northwest region of Vietnam for their antimicrobial activities against Escherichia coli, Bacillus subtilis, Candida albicans, Aspergillus fumigatus, and Aspergillus flavus. The results showed that 5 strains were antagonistic to Escherichia coli, 22 strains were antagonistic to Bacillus subtilis, 3 strains were antagonistic to all the three test fungi, 6 strains were antagonistic to more than one test microorganism, and 2 strains were antagonistic to all test microorganisms. Three actinomycetous strains (AL12.3, AT4.1, and AS10.10) with outstanding activities were identified as Streptomyces spp. The optimal conditions for their growth were determined to be as follows: ISP4 medium with potato extract, temperature at 30 °C, culture duration of 6-7 days for strain AL12.3, and 3-4 days for strains AT4.1 and AS10.10. A preliminary experiment in this study showed that when cultured on a medium supplemented with the aqueous extract of its cognate plant, strain AT4.1 displayed an enhanced antibacterial activity against
E. coli and B. subtilis, compared to culture conditions without the extract.
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