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First name: Miriam
Last name: Sadowski
Country: Germany
Thesis Subject:
Molecular characterization of ectosymbiotic bacteria from nematodes in shallow water systems
10/2011 - 03/2013 M.Sc. in Marine Microbiology
International Max Planck Research School of Marine Microbiology (MarMic)
10/2007 - 06/2011 B.Sc. in Biotechnology
Lausitz University of Applied Sciences
09/2005 - 07/2007 Chemical-technical assistant (focussed on biotechnology)
BSZ Dippoldiswalde
Scientific Interests and Goals:
Stilbonematid nematodes are highly abundant members of the meiofauna in coastal sediments. These nematodes are covered by sulfur-oxidizing ectosymbiotic bacteria. Co-occuring stilbonematid nematodes of various genera have been described from sandy sediments of the mediterranean island of Elba (Italy), but nothing is known about their ectosymbiotic bacteria. My aim is to characterize the nematodes and their ectosymbiotic bacteria with molecular methods. Phylogenetic analysis of the host, based on the 18S rRNA gene showed that at least four different genera co-occur in the same habitat. Each of the nematodes hosts was covered by a particular arranged bacterial coat consisting of a certain morphotype. Nematodes of the genus Catanema, for example, are covered by a monolayer of rods, whereby Eubostrichus sp. has long filamentous bacteria on the cuticle. Phylogenetic analyses, based on the 16S-23S-ITS region, showed that nematodes of different genera are associated with distinct ectosymbiotic bacteria belonging to a gammaproteobacterial clade of sulfur-oxidizing symbionts from marine nematode and oligochaete worms. Each of the stilbonematid nematode genera was associated with its own particular 16S-23S-ITS type. Moreover individuals of two different Leptonemella sp. hosted two closely related but distinct ectosymbionts, indicating that the symbiotic associations are host species-specific. While highly monospecific associations were shown for the genera Leptonemella and Catanema, Laxus sp., Eubostrichus sp. and Stilbonema sp. had a higher diversity in their bacterial community. To exclude that these other bacteria are contaminants and show that the gammaproteobacterial bacteria are the major ectosymbionts, fluorescence in-situ hybridization (FISH) with specific probes will be performed.
Selected Publications: