General research aim

The research at the department of Microbiology is aimed at studying the diversity and activity of microorganisms in their natural environment, their mutual interactions and their survival and adaptation strategies. The research is focused on the microbial ecology of freshwater systems and in particular on the microbial processes at the very dynamic oxic/anoxic interface between the sediment and the water column. In addition to the ecological aspects, also the biochemistry (proteome), molecular biology (genome, transcriptome), cell biology and (eco)physiology of relevant trophic groups of bacteria involved in the nitrogen, sulfur and methane cycles are studied.

Nitrogen cycle

A major research topic is the microbial nitrogen cycle and more specific, the chemolithoautotrophic bacteria active in this cycle: in the first place anaerobic ammonium oxidizers (anammox), but also aerobic ammonium oxidizers and aerobic nitrite oxidizers. We investigate the interactions of these three groups of autotrophs at the oxic/anoxic interface, and their application in wastewater treatment. The research on anammox is one of the main projects of our group and was recently awarded with an ERC advanced grant. With the discovery of anaerobic ammonium oxidation (anammox) a missing link was found in the nitrogen cycle. In the anammox process, ammonium and nitrite are converted into dinitrogen gas with hydrazine (a rocket fuel) as an intermediate. Anammox has high potential in waste water treatment. Our department investigates many aspects of the anammox process: enzymes involved in the reaction (including proteomics), response to environmental changes (transcriptomics), functional analysis of anammox cell compartmentalization, ecological significance of anammox bacteria in natural ecosystems and application of anammox bacteria in waste water treatment.

Sulfur cycle

Volatile sulfur compounds are very malodorous and toxic, and are also produced in a number of industrial processes. Furthermore, they have a major impact on global warming and acid precipitation processes. The research is focused on the microbial degradation of volatile organic sulfur compounds. Studies of the degradation are coupled to the application of promising bacterial isolates in treatment of polluted air.

Methane cycle

Methane oxidizing bacteria (methanotrophs) utilize methane as their sole source of carbon and energy. Methanotrophs play an important role in the oxidation of methane in natural environments (wetlands, freshwater systems, geothermal regions). This research is conducted in close cooperation with the Department of Aquatic Ecology and Environmental Biology and focuses on the function, identity and ecophysiology of both aerobic and anaerobic methanotrophic bacteria in wetland ecosystems.