| || || Amon, Ngetem Bobai|
| || || Solid-phase cultivation and co-cultivation : inducing bioactive secondary metabolities production in marine actinomycetes|
Author:Amon, Ngetem Bobai
Institution: University of the South Pacific.
Subject: Actinobacteria -- Fiji, Marine metabolites -- Fiji
Call No.: Pac QR 82 .A35 A46 2013
Copyright:Over 80% of this thesis may be copied without the authors written permission
Abstract: Marine actinomycetes including the genus Salinispora are potential sources of industrial and therapeutic agents. The present study aims to explore whether solid phase cultivation or co-cultivation induce the production of bioactive compounds in strains with marine actinomycetes-like morphology which produce inactive extracts by the liquid culture technique. The sediment samples were collected within Fiji Islands, and actinomycetes strains were isolated using the heat-shock and stamping methods on M1A media. Strain selection was based on previous inactivity against wild type Staphylococcus aureus (WTSA), methicilin resistant S. aureus (MRSA), vancomycin resistant Enterococcus faecium (VREF), amphoterecin resistant Candida albicans (ARCA) and wild type C. albicans (WTCA) and brine shrimp cytotoxicity, while the control strain shows bacterial activity and mild cytotoxicity. The Salinispora-like morphology strains were cultured on solid M1A media at three time intervals and extracted by solid culture extraction technique as well as liquid culture extraction technique for comparison. The crude extracts of the strains were tested against microbial pathogens using the disc diffusion method and brine shrimp assay. Secondary metabolites were screened using thin layer chromatography (TLC) and liquid chromatography-mass spectroscopy (LC-MS). Day old cultures of marine microbes were cultured with inactive marine actinomycetes strains. The mixed cultures were extracted and tested for antibacterial, antifungal and brine shrimp cytotoxicity. Solid phase cultivation and solid culture extraction did not generally induce secondary metabolites production in the inactive Salinispora-like morphology strains; but increased anti-bacterial activity in active Salinispora-like morphology strains, and induced mild cytotoxicity in one of the inactive Salinispora-like morphology strain and the control strain. The control Salinispora-like morphology strain produced similar metabolites in both solid and liquid cultures. The Salinispora-like morphology strains took approximately six weeks to sporulate after inoculation onto solid M1A media. The cocultivation of marine actinomycetes showed no significant bioactivity against the tested pathogens, but mild cytotoxicity for some mixed cultures.