Screening of anti-microbial activity of secondary metabolites extracted from Crinum macowanii and its associated bacterial endophytes

M.Tech. (Biotechnology)Abstract: Medicinal plants produce several secondary metabolites, which are significant in drug development. Crinum macowanii is a medicinal plant distributed in Zimbabwe, South Africa, Mozambique, Swaziland, Botswana, Zambia, Kenya and Malawi. C. macowanii is used to heal sexually transmitted diseases, backaches and stimulate lactation in women and cows. However, excessive use of medicinal plants for drug development could lead to plant species extinction and deforestation. The endophytes, bacterial and fungal species residing within the plant hosts, produce novel compounds similar to their plant hosts, which can be used in drug development. In this study, five bacterial endophytes were isolated from surface sterilised plant organs of the medicinal plant C. macowanii. Gram staining technique, scanning electron microscope and sequencing of 16S rRNA genes were used to identify the endophytes. The isolates were Staphylococcus sp. C2, Staphylococcus sp. C3, Bacillus sp. C4, Acinetobacter sp. C5 and Staphylococcus sp. C6. Antibacterial activities of each endophyte were assessed against Gram-negative strains Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853) and Klebsiella pneumoniae (ATCC 13182); Grampositive Staphylococcus aureus (NCTC 6571) and Bacillus cereus (ATCC 10876) using the disk diffusion method with Streptomycin used as a positive control. The crude extracts of all the endophytes showed varying degrees of activity against all the test strains, except against Klebsiella pneumoniae. Phytochemical analysis of C. macowanii and associated bacterial endophytes varied slightly with presence of alkaloids. The Liquid Chromatography Quadrupole Time of Flight Mass Spectrometry (LCQTOF/MS) data showed that bacterial endophytes and C. macowanii have similar metabolites, which was based on having similar molecular formula and mass. However, based on few identified metabolites of bacterial endophytes and C. macowanii, the extraction methods used in this study need to be improved. This study contributed towards exploring metabolites from bacterial endophytes, which present a potential natural source for metabolites that can be used in drug discovery or applied for agricultural purposes