Diversity of Easter Island Actinobacteria and their secondary metabolites.

Sottorff, Ignacio (2019) Diversity of Easter Island Actinobacteria and their secondary metabolites. Open Access (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 193 pp.

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Abstract

Easter Island is a geographically isolated location in the South Pacific Ocean, which has remained unstudied in microbiological terms. Actinobacteria are Gram-positive bacteria which are widely recognized by producing chemicals with medical applications and having a wide environmental distribution. Marine actinobacterial representatives have shown large potential for the production of biological active chemicals. Therefore, this study focuses in the isolation and characterization of the culturable actinobacterial diversity dwelling in the coastal zone of Easter Island, as well as in the chemical analysis of the secondary metabolites produced by actinobacterial representatives. To develop this project, we used a wide variety of culture media which had different nutritive conditions in order to broaden the diversity of cultured Actinobacteria. The identification and classification of the isolates was developed on the basis 16S rRNA genetic marker. For the evaluation of the chemical profiles, as well as the purification and identification of pure molecules we used techniques of analytic chemistry like chromatography, mass spectroscopy and nuclear magnetic resonance. Our results indicated that Easter Island had a large Actinobacteria diversity, since we obtained a total of 163 pure cultures, which represented 72 phylotypes distributed in 20 different genera. Phylogenetic evaluation suggested a high degree of novelty showing that 45% of the isolates may represent new taxa. The chemical evaluation of an Easter Island sea anemone and its actinobacterial symbionts showed the presence of two known antitumoral anthraquinones. Chemical experiments showed that the real producer of the anthraquinones was a previously unidentified actinobacterial strain, and not the sea anemone. In addition, the study of two Streptomyces strains, which were geographically distant, but phylogenetically almost identical, indicated that they had different morphological and chemical features which were strain specific. Finally, our study showed that Easter Island was a rich source of new actinobacterial taxa, as well as of known representatives. The chemically studied Actinobacterial representatives showed interesting potential for the production of antitumoral and antibiotic chemicals and the secondary metabolite comparison of phylogenetical identical, but geographical distant, Actinobacteria clarified that 16S rRNA is not a suitable genetic marker to determine chemical novelty potential.

Document Type: Thesis (PhD/ Doctoral thesis)
Thesis Advisor: Imhoff, Johannes F. and Hentschel, Ute
Keywords: Easter Island, Actinobacteria, Chile, secondary metabolites, diversity, natural products, NMR, HRLCMS, culture approach
Research affiliation: OceanRep > GEOMAR > FB3 Marine Ecology > FB3-MS Marine Symbioses
Date Deposited: 14 Jun 2019 10:31
Last Modified: 16 Nov 2022 08:26
URI: https://oceanrep.geomar.de/id/eprint/46924

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