| || || Ginigini, Joape G. M|
| || || Analysis of the antibiotic activities of salinispora strains from marine sediment as a guide to new phylogenetic and chemical diversity|
Author:Ginigini, Joape G. M
Institution: University of the South Pacific.
Call No.: pac In Process
Copyright:Under 10% of this thesis may be copied without the authors written permission
Abstract: The Salinispora genus previously reported as the first obligate marine actinomycete was recently identified at the species level by the characteristic secondary metabolites they produce (chemotype). A small percentage of strains within the species level of the genus showed new sequence types which are typically reflected in the production of added secondary metabolites. A classical chemical profiling technique known as TLC-Bioautography was employed to facilitate both species recognition as well as the presence of unique metabolites present within a species level. This allows a metabolite grouping of unknown strains to known standards. Results from this approach were compared to genetic analysis using 16S rRNA sequencing to reveal species diversity and thus possible metabolite diversity of the isolated strains. Sediment samples collected from the Pacific Ocean in the Fiji archipelago were plated on isolation media and the resulting bacterial colonies were cultured under conditions favourable for actinomycete growth. Samples fitting the Salinispora morphotype were (based on appearance and their obligate growth behaviour towards 0.45um filtered 100% seawater media) isolated and purified. These suspected Salinispora strains (100 in number) were fermented and the crude cultures screened against resistant pathogenic bacteria and fungi. Screening results assisted in identification of new strain secondary metabolite profiles as compared to the known Salinispora standards. Of the 100 strains for the project, 29 showed unusual profiles on TLC-bioautography. Sequencing of these 29 strains showed 26 (89.7%) with 99-100% homology with S. arenicola while 2 (6.9%) strains showed 99-100% homology to S. pacifica. Furthermore, 2 (6.9%) strains appeared to be new sequence types for S. pacifica according to 16S rRNA sequence results matching (100%) maximum identity to sponge-isolated Salinispora strains deposited in The National Center for Biotechnology Information (NCBI) GenBank designated with YPKC collection ID. These results are contrary to present knowledge of the S. pacifica species pharmacology.