• 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

  • Microbial Symbioses

    University of Vienna PhD program

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Dome News

Latest publications

Flow-through stable isotope probing (Flow-SIP) minimizes cross feeding in complex microbial communities

Stable isotope probing (SIP) is a key tool for identifying the microorganisms catalyzing the turnover of specific substrates in the environment and to quantify their relative contributions to biogeochemical processes. However, SIP based studies are subject to the uncertainties posed by cross-feeding, where microorganisms release isotopically labelled products, which are then used by other microorganisms, instead of incorporating the added tracer directly. Here, we introduce a SIP approach that has the potential to strongly reduce cross-feeding in complex microbial communities. In this approach, the microbial cells are exposed on a membrane filter to a continuous flow of medium containing isotopically labelled substrate. Thereby, metabolites and degradation products are constantly removed, preventing consumption of these secondary substrates. A NanoSIMS-based proof-of-concept experiment using nitrifiers in activated sludge and 13C-bicarbonate as an activity tracer showed that Flow-SIP significantly reduces cross-feeding and thus allows distinguishing primary consumers from other members of microbial food webs.

Kitzinger K, Mooshammer M, Schintlmeister A, Ahmerkamp S, Nielsen J, Nielsen PH, Wagner M
2020 - ISME J, in press

Exploring the upper pH limits of nitrite oxidation: diversity, ecophysiology, and adaptive traits of haloalkalitolerant Nitrospira

Nitrite-oxidizing bacteria of the genus Nitrospira are key players of the biogeochemical nitrogen cycle. However, little is known about their occurrence and survival strategies in extreme pH environments. Here, we report on the discovery of physiologically versatile, haloalkalitolerant Nitrospira that drive nitrite oxidation at exceptionally high pH. Nitrospiradistribution, diversity, and ecophysiology were studied in hypo- and subsaline (1.3-12.8 g salt/l), highly alkaline (pH 8.9-10.3) lakes by amplicon sequencing, metagenomics, and cultivation-based approaches. Surprisingly, not only were Nitrospira populations detected, but they were also considerably diverse with presence of members of Nitrospira lineages I, II and IV. Furthermore, the ability of Nitrospira enrichment cultures to oxidize nitrite at neutral to highly alkaline pH of 10.5 was demonstrated. Metagenomic analysis of a newly enriched Nitrospira lineage IV species, “Candidatus Nitrospira alkalitolerans”, revealed numerous adaptive features of this organism to its extreme environment. Among them were a sodium-dependent N-type ATPase and NADH:quinone oxidoreductase next to the proton-driven forms usually found in Nitrospira. Other functions aid in pH and cation homeostasis and osmotic stress defense. “Ca. Nitrospira alkalitolerans” also possesses group 2a and 3b [NiFe] hydrogenases, suggesting it can use hydrogen as alternative energy source. These results reveal how Nitrospira cope with strongly fluctuating pH and salinity conditions and expand our knowledge of nitrogen cycling in extreme habitats.

Daebeler A, Kitzinger K, Koch H, Herbold CW, Steinberger M, Schwarz J, Zechmeister T, Karst S, Albertsen M, Nielsen PH, Wagner M, Daims H
2020 - ISME J, in press

Composition and activity of nitrifier communities in soil are unresponsive to elevated temperature and CO2, but strongly affected by drought

Nitrification is a fundamental process in terrestrial nitrogen cycling. However, detailed information on how climate change affects the structure of nitrifier communities is lacking, specifically from experiments in which multiple climate change factors are manipulated simultaneously. Consequently, our ability to predict how soil nitrogen cycling will change in a future climate is limited. We conducted a field experiment in a managed grassland and simultaneously tested the effects of elevated atmospheric COand temperature, and drought on the abundance of active ammonia-oxidizing bacteria (AOB) and archaea (AOA), comammox (CMX) Nitrospira, and nitrite-oxidizing bacteria (NOB), and on gross mineralization and nitrification rates. We found that N transformation processes, as well as gene and transcript abundances, and nitrifier community composition were remarkably resistant to individual and interactive effects of elevated COand temperature. During drought however, process rates were increased or at least maintained. At the same time, the abundance of active AOB increased probably due to higher  NH4availability. Both, AOA and comammox Nitrospira decreased in response to drought and the active community composition of AOA and NOB was also significantly affected. In summary, our findings suggest that warming and elevated COhave only minor effects on nitrifier communities and soil biogeochemical variables in managed grasslands, whereas drought favors AOB and increases nitrification rates. This highlights the overriding importance of drought as a global change driver impacting on soil microbial community structure and its consequences  for N cycling.

Séneca J, Pjevac P, Canarini A, Herbold CW, Zioutis C, Dietrich M, Simon E, Prommer J, Bahn M, Pötsch E, Wagner M, Wanek W, Richter A
2020 - ISME J, in press

Lecture series

Ecology of ammonia oxidizers in engineered aquatic environments

Josh Neufeld
Department of Biology, University of Waterloo, Canada
19.03.2020
12:00 h
Webinar

Ammonia oxidising archaea: From environments to enzymes

Laura Lehtovirta-Morley
University of East Anglia
30.01.2020
12:00 h
Lecture Hall HS2, UZA1, Althanstrasse 14, 1090 Wien

Metals and microbial respiration: the molecular basis of bioelectricity production and greenhouse gas destruction

David Richardson
University of East Anglia, Norwich Research Park, Norwich, UK
23.01.2020
12:00 h
Lecture Hall HS2, UZA1, Althanstrasse 14, 1090 Wien