Dr. Christopher Sedlacek

Dr. Chris Sedlacek
University of Vienna
Department of Microbiology and Ecosystem Science
Division of Microbial Ecology
A-1090 Vienna

Research Interests and Background

Currently, my research interests are focused on investigating the ecophysiological and genomic characteristics of microorganisms involved in nitrification (nitrifiers): ammonia-oxidizing bacteria and archaea, nitrite-oxidizing bacteria, and the recently discovered comammox bacteria. Nitrifiers play a key role in the global biogeochemical nitrogen cycle, transforming ammonia (NH3) via nitrite (NO2-) to nitrate (NO3-). Nitrification is ubiquitous in the environment and is utilized in engineered systems such as wastewater treatment plants and aquaculture systems. However, nitrification also contributes to nitrogen (fertilizer) loss from agricultural systems through nitrogen leaching, run-off, and nitrogenous greenhouse gas emissions (N2O, NO), as a consequence of the excessive application of nitrogen-based fertilizers. Moreover, nitrogen leaching and run-off leads to the eutrophication of downstream aquatic ecosystems. Therefore, my goal is to better understand the underlying genomic and physiological traits of nitrifiers, in order to inform nitrification management practices in both engineered and natural ecosystems.

To address this goal, I utilize a suite of molecular and culture dependent techniques such as: comparative genomics, growth or activity assays, microrespirometry, environmental species enrichment (isolation), fluorescent in situ hybridization (FISH), RAMAN microspectroscopy, and chemostat cultivation. These techniques enable me to investigate and characterize nitrifiers from their initial detection in environmental samples to their growth characteristics once isolated and at each stage in between. I’m currently focused on the isolation of several novel nitrifiers from multiple environments, the characterization of nitrifier substrate kinetics, as well as the genomic and physiologic investigation of alternative metabolisms in nitrifiers.

In addition to nitrification specific topics, I also have general research interests connected to my previous research projects, which include the cultivation of currently unculturable or fastidious microbes, microbial community interactions, and microbial adaptations to extreme environments or stress.

Current Projects

I’m involved in several ongoing projects, which are outlined on the pages of Michael Wagner and Holger Daims.

Select publications from ongoing projects

Kits KD, Sedlacek CJ, Lebedeva EV, Han P, Bulaev A, Pjevac P, Daebeler A, Romano S, Albertsen M, Stein LY, Daims H, Wagner M. 2017. Kinetic analysis of a complete nitrifier reveals an oligotrophic lifestyle. Nature, 549: 269-272.

Daebeler A, Herbold CW, Vierheilig J, Sedlacek CJ, Pjevac P, Albertsen M, Kirkegaard RH, De La Torre JR, Daims H, Wagner M. 2018. Cultivation and Genomic Analysis of “Candidatus Nitrosocaldus islandicus,” an Obligately Thermophilic, Ammonia-Oxidizing Thaumarchaeon from a Hot Spring Biofilm in Graendalur Valley, Iceland. Front. Microbiol. 9:193.