Chiang Mai Journal of Science

Natural products derived from endophytic microorganisms are one possible source for a new array of drug candidates. In this study, an endophytic Bacillus amyloliquefaciens UD25 was isolated and identified from a medicinal plant (Memecylon edule Roxb). Crude ethyl acetate extract of a whole culture of B. amyloliquefaciens UD25 demonstrated growth inhibition of pathogenic bacteria, including Streptococcus sp., methicillin resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, Bacillus cereus and Escherichia coli. The antibiotic compounds were analyzed by GC-MS. Eighteen multifunctional natural product derivatives were identified including carboxylic acid and ester (1-4, 8-9, 12-13, 15), anthaquinone (5), alkaloids (7, 10-11),  organohalogen  (17), carbonyl (6,14, 16) and thiol (18). The antibiotic compounds observed by scanning electron microscope (SEM) had an impact on the cell membranes, which wilted and collapsed the cell surface. These results may lead to an alternative source of new antibacterial drugs candidates from endophytic bacteria.