Item type:Thesis, Open Access

Sphaeroidkörper der Diatomee Rhopalodia gibba Obligate Endosymbionten zur molekularen Stickstofffixierung

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Date

2004-12-14

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Philipps-Universität Marburg
DOI

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Abstract

The diatom Rhopalodia gibba harbours unusual cell inclusions which are transmitted vertically to the next generation. Morphological analyses of these so-called spheroid bodies lead to the assumption that they are either organelles or intracellular bacteria, which might be associated with the diatoms capacity to fix molecular nitrogen. In this work we characterize the spheroid bodies of R. gibba as obligate intracellular bacteria of cyanobacterial origin. Phylogenetic studies revealed the closest freeliving relative of these endosymbionts, the unicellular, diazotrophic cyanobacterium Cyanothece sp. ATCC 51142. Using different experimental analyses we could assign the ability of nitrogen fixation of the diatom to the spheroid bodies. According to their endosymbiontic nature, the spheroid bodies show physiological adaption or reduction, respectively. A comparative genome sequencing project between spheroid bodies and Cyanothece sp. was used to determine the genome evolution of the endosymbionts. Analysis of the nif gene- and flanking regions of both organisms revealed multiple genomic modifications on the endosymbionts genome, e.g. gene inactivation and modification, but also appearance of unusual large non-coding DNA stretches, which were identified as regions of massive gene loss by accumulation of mutations. The reductive genome evolution and the loss of physiological capacities characterize the spheroid bodies as obligate and permanent endosymbionts. They are therefor the first obligate and permanent endosymbionts for nitrogen fixation described so far and could be used as model system for investigating the process of establishing endosymbiontic interaction and endosymbiont genome evolution.

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Dates
Created: 2004Issued: 2004-12-14Updated: 2011-08-10
Faculty
Fachbereich Biologie
Language
ger
Data types
DoctoralThesis
Keywords
Genome evolutionEndosymbiosisGenomevolutionNitrogen fixation
DFG-subjects
EndosymbioseStickstofffixierung
DDC-Numbers
570
License
https://rightsstatements.org/vocab/InC-NC/1.0/
URI
https://open.uni-marburg.de/handle/10.17192/z2004.0632
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Kneip, Christoph: Sphaeroidkörper der Diatomee Rhopalodia gibba Obligate Endosymbionten zur molekularen Stickstofffixierung. : Philipps-Universität Marburg 2004-12-14. DOI: https://doi.org/10.17192/z2004.0632.

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This item has been published with the following license: In Copyright