Degree: Master of Science in Biology
Researcher: Mr. Joape Ginigini
Thesis title: The Analysis of the Antibiotic Activities of Salinispora Strains from Marine Sediment as a Guide to New Phylogenetic and Chemical Diversity
Principal Supervisor: Prof. William Aalbersber and Dr. Paul Jensen (UCSD, Scripps Institute of Oceanography)
Status: Completed in 2012
The Actinomycete group of bacteria are known to produce antitumor, immune suppressive agents and enzymes (Lam, 2006) and also antibiotic compounds. The genus Salinispora belonging to the actinomycete family Micromonosporaceae, has been found to contain highly potent anticancer compounds, an example of which is Salinisporamide A produced by S. Tropica currently in stage II clinical trials. Only 3 species have been found so far namely S. tropica, S. arenicola and S. pacifica, with each of them producing distinctive compounds. Thus, hypothetically one could discover new Salinispora species by looking for strains that make new metabolites at the Salinispora genus level.
The project involved the chemotaxonomic study of one hundred bioactive marine derived Salinispora bacteria collected from 9 provinces and isolated from 80 marine sediment samples in the Fiji Islands. Strains were cultured in a modified media formulation (M1A) for culturing actinomycetes. After morphological examination on agar, biochemical testing and seawater growth requirement tests, actinomycete strains fitting the Salinispora morphology and chemotype were selected for chemical analyses. The Salinispora strains were further tested for antibiotic activity against VREF, MRSA, WTSA, ARCA , WTCA drug resistant pathogenic bacteria and fungi. Cytotoxicity tests were also applied to the ferment extracts by means of the brine shrimp assay. Bioassay active extracts were then subjected to exploratory TLC-bioautography to identify crude extracts/strains that contain unique antibiotic compounds. Strains tentatively detected through this screening process were sent to our collaborators at UCSD Scripps Institute of Oceanography for 16S rRNA sequencing to confirm presence of any new species. Comparison of chemotypic and phylogenetic data was the applied to reveal existant diversity patterns for the Salinispora bacteria.