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Evolution, ecophysiology and molecular basis of bacterial multicellularityEvolution, Ökophysiologie und molekulare Basis bakterieller Multizellularität

Heterologous bacterial multicellularity in phototrophic consortia

Phototrophic consortia consist of a fixed number of Green Sulfur Bacteria epibionts surrounding a central colorless rod-shaped betaproteobacterium. Our group established the first laboratory cultures of phototrophic consortia which represent the only laboratory model system currently available for the study of highly specific interactions between nonrelated bacteria. Both partners divide in a highly coordinated manner. The entire consortium swims towards the light (scotophobic response) which the epibionts need for anoxygenic photosynthesis, whereas the central bacterium provides the necessary motility. The cells form specific cell-cell-adhesion structures and exchange multiple signals. Recent ultrastructural analyses have provided evidence for intracellular sorting of antenna structures in the epibiont cells, which occurs exclusively when they are in the symbiotic state. "Symbiosis genes" of the epibiont were identified by genomic approaches. Putative large exoproteins and a putative protein with a RTX toxin-type ß-roll could be identified. So far, such genes have not been found in any of the free living green sulfur bacteria, indicating a specific role in the interaction.

Homologous bacterial multicellularity in multicellular magnetotactic prokaryotes (MMPs)

Multicellular magnetotactic prokaryotes (MMPs) represent highly organised, spherical and motile aggregates of 10-40 bacterial cells containing magnetosomes. Although composed of different cells, each with its own magnetosomes and flagellation, MMPs orient themselves within a magnetic field and exhibit magnetotaxis, indicating signal exchange between the cells. Within each aggregate, the magnetosome chains of individual cells are oriented in the same direction. 16S rRNA gene sequence analysis revealed a single phylotype. Fluorescence in situ hybridisation with a specific oligonucleotide probe revealed that the aggregates are composed of cells of the same phylotype. Genes for dissimilatory sulfite reductase (dsrAB) and dissimilatory adenosine-5´-phosphate reductase (aprA) could be detected in purified MMP samples, suggesting that MMPs are capable of sulfate reduction. Chemotaxis assays with 41 different test compounds yielded strong responses towards acetate and propionate. By means of its coordinated magnetotaxis and chemotaxis, MMPs are well adapted to the steep chemical gradients which are characteristic for intertidal marine sediments.

Representative publications

  • Müller, J., Overmann J. (2011) Close interspecies interactions between prokaryotes from sulfureous environments. Frontiers Microb Physiol Metabol 2-146
  • Overmann, J. (2006) (editor) Molecular Basis of Symbiosis. And Chapter II (p.21-37): The symbiosis between nonrelated bacteria in phototrophic consortia. Progress in Molecular Subcellular Biology, Springer-Verlag
  • Pfannes K.R., Vogl, K., Overmann J. (2007) Heterotrophic symbionts of phototrophic consortia: members of a novel diverse cluster of Betaproteobacteria characterised by a tandem rrn operon structure. Environ. Microbiol. 9: 2782-2794
  • Vogl, K., Wenter, R., Dreßen, M., Schlickenrieder, M., Plöscher, M., Eichacker, L., Overmann, J. (2008). Identification and analysis of four candidate symbiosis genes from "Chlorochromatium aggregatum", a highly developed bacterial symbiosis. Environ. Microbiol. 10: 2842-2856
  • Wanner, G., Vogl, K., Overmann, J. (2008) Ultrastructural characterization of the prokaryotic symbiosis in "Chlorochromatium aggregatum". J. Bacteriol. 190: 3721-3730
  • Wenter, R., Wanner, G., Schüler, D., Overmann, J. (2009) Ultrastructure, phylogeny and tactic behaviour of a novel multicellular magnetotactic prokaryote from North Sea sediments. Environ. Microbiol. 11: 1493-1505
  • Wenter, R., Hütz, K., Dibbern, D., Reisinger, V., Li, T., Plöscher, M., Eichacker, L., Eddie, B., Hanson, T., Bryant, D., Overmann, J. (2010) Expression-based identification of genetic determinants of the bacterial symbiosis in `Chlorochromatium aggregatum´. Environ. Microbiol. 12: 2259-2276
Photo of Jörg  Overmann
Prof. Dr. Overmann, Jörg
Phone: +49-531/2616-352

Scientific Director / Wissenschaftlicher Direktor

Photo of Petra  Henke
Dr. Henke, Petra
Phone: +49-531/2616-382
Photo of Hendrik  Reuper
Reuper, Hendrik
Phone: +49-531/299-3789

PhD Student - Junior Research Group "VirusInteract" (Stress granules project)