Nachweis von Biosynthesegenen des bakteriellen Sekundärstoffwechsels sowie Isolierung und Strukturaufklärung von Naturstoffen aus ausgewählten Actinomyceten

Schneemann, Imke (2011) Nachweis von Biosynthesegenen des bakteriellen Sekundärstoffwechsels sowie Isolierung und Strukturaufklärung von Naturstoffen aus ausgewählten Actinomyceten (Doctoral thesis/PhD), Christian-Albrechts-Universität, Kiel, Germany, 198 pp

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Abstract

Bacteria, especially Actinobacteria, are one of the most important producers of structurally diverse and biologically active natural products, which are of great significance for pharmaceutical applications. Many secondary metabolites are synthesized by bacteria living in association with a macroorganism. Among others, marine sponges shelter a rich community of microorganisms. Actinomycetes (in the following used as synonym for the order Actinomycetales or the class Actinobacteria) isolated from the marine sponge Halichondria panicea as well as other marine and terrestrial Actinomycetes were investigated according to their ability to produce well-established and unknown secondary metabolites to characterize bacterial capability of producing natural products. A phylogenetic classification of Actinomycetes isolated from H. panicea was completed within the first part of this thesis. Strains were assigned to the genera Actinoalloteichus, Micrococcus, Micromonospora, Nocardiopsis and Streptomyces. Subsequently, the secondary metabolite pattern, the presence of NRPS and type II PKS gene fragments as well as the biological activity of raw extracts of all strains were investigated. In conclusion, sponge associated Actinomycetes and particularly those with an NRPS or PKS gene fragment, were effective producers of biologically active natural products. Subsequently, with three of the investigated strains, cultivation and stimulation experiments were carried out to provide detailed chemical profiles. Two of these, Streptomyces sp. HB202 and Nocardiopsis sp. HB383, were notably affected by different culture conditions and showed an enormous potential to produce known as well as novel substances. Using HPLC-UV/MS and NMR-spectroscopy, mayamycin, an aromatic polyketide, of Streptomyces sp. HB202, and four new γ-pyrones, of Nocardiopsis sp. HB383, nocapyrones A-D, were isolated and structually characterized. Their biological activity was determined and the biosynthesis of nocapyrone A was investigated by feeding experiments. In the second part of this thesis, the genetic analysis regarding the presence of NRPS and type II PKS gene fragments was extended by an additional primer system amplifying a phenazine gene fragment. The relevance of the genetic information was validated by cultivation experiments and chemical analysis of selected, phylogenetically diverse, strains. As a result, marine Actinomycetes seem to be ideal for investigations using the designed molecular biological system The wide range of proven methods was applied by investigating Nocardia jejuensis DSM 44959T. Using further cloning experiments, NRPS and type II PKS gene fragments were identified. Subsequent cultivation approaches reveal among known metabolites two novel mycobactines, brasilibactin C and D. After the structural characterization of the investigated products, biological activities of the metabolites were tested.

Document Type: Thesis (Doctoral thesis/PhD)
Thesis Advisors: UNSPECIFIED
Keywords: Microbiology; nicht-ribosomale Peptid-Synthetase, Polyketid-Synthase, Phenazine, Actinomyceten, Wirkstoffe, Schwamm
Research affiliation: OceanRep > GEOMAR > FB3 Marine Ecology > FB3-MI Marine Microbiology
Date Deposited: 01 Dec 2011 08:23
Last Modified: 06 Jul 2012 15:02
URI: http://eprints.uni-kiel.de/id/eprint/12674

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