• We seek to understand

    the role of microorganisms in Earth's nutrient cycles

    and as symbionts of other organisms

  • Cycling of carbon, nitrogen and sulfur

    affect the health of our planet

  • Ancient invaders -

    Bacterial symbionts of amoebae

    and the evolution of the intracellular lifestyle

  • The human microbiome -

    Our own social network of microbial friends

  • Single cell techniques offer new insights

    into the ecology of microbes

  • Apply for the DOME International PhD/PostDoc program

Dome News

Latest publications

Plastid establishment did not require a chlamydial partner

Primary plastids descend from the cyanobacterial endosymbiont of an ancient eukaryotic host, but the initial selective drivers that stabilized the association between these two cells are still unclear. One hypothesis that has achieved recent prominence suggests that the first role of the cyanobiont was in energy provision for a host cell whose reserves were being depleted by an intracellular chlamydial pathogen. A pivotal claim is that it was chlamydial proteins themselves that converted otherwise unusable cyanobacterial metabolites into host energy stores. We test this hypothesis by investigating the origins of the key enzymes using sophisticated phylogenetics. Here we show a mosaic origin for the relevant pathway combining genes with host, cyanobacterial or bacterial ancestry, but we detect no strong case for Chlamydiae to host transfer under the best-fitting models. Our conclusion is that there is no compelling evidence from gene trees that Chlamydiae played any role in establishing the primary plastidendosymbiosis.

  • Domman D, Horn M, Embley TM, Williams TA
2015 - Nat. Commun., 6: 6421

Improved isolation strategies allowed the phenotypic differentiation of two Nitrospira strains from widespread phylogenetic lineages.

The second step of nitrification, the oxidation of nitrite to nitrate, is vital for the functioning of the nitrogen cycle, but our understanding of the ecological roles of the involved microorganisms is still limited. The known diversity of Nitrospira, the most widely distributed nitrite-oxidizing bacteria, has increased remarkably by analyses of 16S rRNA and functional gene sequences. However, only few representatives could be brought into laboratory cultures so far. In this study, two Nitrospira from activated sludge were isolated using novel approaches together with established methods. Highly enriched 'Candidatus Nitrospira defluvii' was separated from concomitant heterotrophs by taking advantage of its resistance against ampicillin and acriflavine. Beside this member of lineage I, a novel species of lineage II, named N. lenta, was initially enriched at 10°C and finally purified by using optical tweezers. The tolerance to elevated nitrite levels was much higher in N. defluvii than in the more fastidious N. lenta and was accompanied by pronounced biofilm formation. Phylogenetic classification of 12 additional enrichments indicated that Nitrospira lineage I is common in extreme and moderate ecosystems like lineage II. The new cultures will help to explore physiological and genomic differences affecting niche separation between members of this highly diverse genus.

  • Nowka B, Off S, Daims H, Spieck E
2015 - FEMS Microbiol Ecol., in press

Dimeric chlorite dismutase from the nitrogen-fixing cyanobacterium Cyanothece sp. PCC7425

It is demonstrated that cyanobacteria (both azotrophic and non-azotrophic) contain heme b oxidoreductases that can convert chlorite to chloride and molecular oxygen (incorrectly denominated chlorite 'dismutase', Cld). Beside the water-splitting manganese complex of photosystem II, this metalloenzyme is the second known enzyme that catalyses the formation of a covalent oxygen-oxygen bond. All cyanobacterial Clds have a truncated N-terminus and are dimeric (i.e. clade 2) proteins. As model protein, Cld from Cyanothece sp. PCC7425 (CCld) was recombinantly produced in Escherichia coli and shown to efficiently degrade chlorite with an activity optimum at pH 5.0 [kcat 1144 ± 23.8 s-1 , KM 162 ± 10.0 μM, catalytic efficiency (7.1 ± 0.6) × 106  M-1  s-1 ]. The resting ferric high-spin axially symmetric heme enzyme has a standard reduction potential of the Fe(III)/Fe(II) couple of -126 ± 1.9 mV at pH 7.0. Cyanide mediates the formation of a low-spin complex with kon  = (1.6 ± 0.1) × 105  M-1  s-1 and koff  = 1.4 ± 2.9 s-1 (KD  ∼ 8.6 μM). Both, thermal and chemical unfolding follows a non-two-state unfolding pathway with the first transition being related to the release of the prosthetic group. The obtained data are discussed with respect to known structure-function relationships of Clds. We ask for the physiological substrate and putative function of these O2 -producing proteins in (nitrogen-fixing) cyanobacteria.

  • Schaffner I, Hofbauer S, Krutzler M, Pirker KF, Bellei M, Stadlmayr G, Mlynek G, Djinovic-Carugo K, Battistuzzi G, Furtmüller PG, Daims H, Obinger C
2015 - Mol Microbiol., in press

Lecture series

Mass spectral imaging of metabolites and proteins in host-microbe interactions

Manuel Liebeke
MPI für Marine Mikrobiologie
05.03.2015
12:00 h
Seminar room

Metaproteomics for sub-surface habitats and the intestinal gut microbiota

Dr. Nico Jehmlich
Helmholtz Centre for Environmental Research - UFZ, Leipzig Germany
29.01.2015
12:00 h
Seminar room DOME

First deployment of the European mobile laboratory in the course of the West-African Ebola outbreak

Kilian Stoecker
Bundeswehr Institute of Microbiology
03.11.2014
12:00 h
Seminar room