• Hunting for microbes since 2003

  • 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

  • The human microbiome -

    Our own social network of microbial friends

  • Ancient invaders -

    Bacterial symbionts of amoebae

    and the evolution of the intracellular lifestyle

  • Marine symbioses:

    Listening in on conversations

    between animals and the microbes they can't live without

  • Single cell techniques offer new insights

    into the ecology of microbes

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Dome News

Latest publications

A multicolor fluorescence in situ hybridization approach using an extended set of fluorophores to visualize microorganisms

Fluorescence in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes is a key method for the detection of (uncultured) microorganisms in environmental and medical samples. A major limitation of standard FISH protocols, however, is the small number of phylogenetically distinct target organisms that can be detected simultaneously. In this study, we introduce a multicolor FISH approach that uses eight fluorophores with distinct spectral properties, which can unambiguously be distinguished by confocal laser scanning microscopy combined with white light laser technology. Hybridization of rRNA-targeted DNA oligonucleotide probes, which were mono-labeled with these fluorophores, to Escherichia coli cultures confirmed that the fluorophores did not affect probe melting behavior. Application of the new multicolor FISH method enabled the differentiation of seven (potentially up to eight) phylogenetically distinct microbial populations in an artificial community of mixed pure cultures (five bacteria, one archaeon, and one yeast strain) and in activated sludge from a full-scale wastewater treatment plant. In contrast to previously published multicolor FISH approaches, this method does not rely on combinatorial labeling of the same microorganisms with different fluorophores, which is prone to biases. Furthermore, images acquired by this method do not require elaborate post-processing prior to analysis. We also demonstrate that the newly developed multicolor FISH method is compatible with an improved cell fixation protocol for FISH targeting Gram-negative bacterial populations. This fixation approach uses agarose embedding during formaldehyde fixation to better preserve the three-dimensional structure of spatially complex samples such as biofilms and activated sludge flocs. The new multicolor FISH approach should be highly suitable for studying structural and functional aspects of microbial communities in virtually all types of samples that can be analyzed by conventional FISH methods.

Lukumbuzya M, Schmid M, Pjevac P, Daims H
2019 - Front Microbiol, 10: 1383

Characterization of a thaumarchaeal symbiont that drives incomplete nitrification in the tropical sponge Ianthella basta

Marine sponges represent one of the few eukaryotic groups that frequently harbor symbiotic members of the Thaumarchaeota, which are important chemoautotrophic ammonia-oxidizers in many environments. However, in most studies, direct demonstration of ammonia-oxidation by these archaea within sponges is lacking, and little is known about sponge-specific adaptations of ammonia-oxidizing archaea (AOA). Here, we characterized the thaumarchaeal symbiont of the marine sponge Ianthella basta using metaproteogenomics, fluorescence in situ hybridization, qPCR and isotope-based functional assays. “Candidatus Nitrosospongia ianthellae” is only distantly related to cultured AOA. It is an abundant symbiont that is solely responsible for nitrite formation from ammonia in I. basta that surprisingly does not harbor nitrite-oxidizing microbes. Furthermore, this AOA is equipped with an expanded set of extracellular subtilisin-like proteases, a metalloprotease unique among archaea, as well as a putative branched-chain amino acid ABC transporter. This repertoire is strongly indicative of a mixotrophic lifestyle and is (with slight variations) also found in other sponge-associated, but not in free-living AOA. We predict that this feature as well as an expanded and unique set of secreted serpins (protease inhibitors), a unique array of eukaryotic-like proteins, and a DNA-phosporothioation system, represent important adaptations of AOA to life within these ancient filter-feeding animals.

Moeller FU, Webster NS, Herbold CW, Behnam F, Domman D, Albertsen M, Mooshammer M, Markert S, Turaev D, Becher D, Rattei T, Schweder T, Richter A, Watzka M, Nielsen PH, Wagner M
2019 - Environmental Microbiology, in press

Indications for enzymatic denitrification to N2O at low pH in an ammonia-oxidizing archaeon

Nitrous oxide (N2O) is a key climate change gas and nitrifying microbes living in terrestrial ecosystems contribute significantly to its formation. Many soils are acidic and global change will cause acidification of aquatic and terrestrial ecosystems, but the effect of decreasing pH on N2O formation by nitrifiers is poorly understood. Here, we used isotope-ratio mass spectrometry to investigate the effect of acidification on production of N2O by pure cultures of two ammonia-oxidizing archaea (AOA; Nitrosocosmicus oleophilus and Nitrosotenuis chungbukensis) and an ammonia-oxidizing bacterium (AOB; Nitrosomonas europaea). For all three strains acidification led to increased emission of N2O. However, changes of 15N site preference (SP) values within the N2O molecule (as indicators of pathways for N2O formation), caused by decreasing pH were highly different between the tested AOA and AOB. While acidification decreased the SP value in the AOB strain, SP values increased to a maximum value of 29‰ in N. oleophilus. In addition, 15N-nitrite tracer experiments showed that acidification boosted nitrite transformation into N2O in all strains, but the incorporation rate was different for each ammonia oxidizer. Unexpectedly, for N. oleophilus more than 50 % of the N2O produced at pH 5.5 had both nitrogen atoms from nitrite and we demonstrated that under these conditions expression of a putative cytochrome P450 NO reductase is strongly upregulated. Collectively, our results indicate that N. oleophilus might be able to enzymatically denitrify nitrite to N2O at low pH.  

Jung M-Y, Gwak J-H, Rohe L, Giesemann A, Kim J-G, Well R, Madsen EL, Herbold CW, Wagner M, Rhee S-K
2019 - ISME J, in press

Lecture series

Viral Intrahost Evolution – a Race in Space and Time

Andreas Bergthaler
CeMM, Research Center for Molecular Medicine of the Austrian Academy of Sciences
06.06.2019
12:00 h
Lecture Hall 2, UZA 1, Althanstr. 14, 1090 Wien

Deciphering population-specific activities of marine microbes with quantitative stable isotope probing

William Orsi
Ludwig-Maximilians-Universität München, Germany
27.05.2019
12:00 h
Lecture Hall HS4, UZA2, Althanstrasse 14, 1090 Wien

Three amazing ideas about microbial biogeography that will blow your mind

Daniel H. Buckley
Cornell University, Ithaca, NY, USA
16.05.2019
12:00 h
Lecture Hall HS2, UZA 1, Althanstrasse 14, 1090 Vienna