Annette Bollmann
Assistant Professor of Microbiology
Research Interests:
My research interests are the isolation, ecology, and physiology of difficult to culture bacteria with special emphasis on bacteria involved in environmentally important processes
Culturing the unculturables: Approximately 99% of the bacteria known by molecular markers have never been cultured in the laboratory. These bacteria exhibit a large source of unknown secondary metabolites and genes involved in bioremediation and other biotechnological interesting processes. A combination of in situ (diffusion chambers) and in vitro methods has been used to cultivate previously uncultured bacteria. These methods have been successfully applied to different environments, like freshwater sediment, contaminated surface sediments and wastewater. Clear differences between the isolates obtained with and without passage of the material through the diffusion chamber were discovered, indicating that the diffusion chamber is a good additional tool to enrich and isolate new bacteria [several publications in prep]. Future projects: - Isolation of bacteria using a combination of in situ and in vitro methods from different environments - Characterization of new and interesting isolates
Pure cultures versus consortia: In nature bacteria populations occur in communities and consortia consisting of assembly's of two (and more) different microorganisms. The bacteria in these consortia interact and perform reactions that no one of the partners can perform alone. Beneficial interactions include commensalism, cross feeding, co metabolism, and signaling. Due to all these interactions microbial consortia can be seen as highly sophisticated units. Future projects: - Consortia in bioremediation - Consortia in general and patterns behind positive inter-actions among bacteria
Ammonia-oxidizing bacteria (AOB) are chemolithoautotrophic bacteria gaining their energy by oxidizing ammonia to nitrite. Ammonia oxidation is the first and very often rate-limiting step in the nitrification process. AOBs can be found in very different environments, like soils, marine and freshwater columns and sediments, and wastewater. My research is focused on AOBs adapted to low ammonium concentrations. These bacteria were enriched in chemostats and used to investigate their competition and starvation behavior, as well as their interactions with heterotrophs [3; 4; in prep]. Future projects: - Whole genome sequence of the new isolate Nitrosomonas sp Is79A3 - Further investigations of the physiology of AOBs adapted to low ammonium concentrations
Selected Publications:
- Bollmann, A. & R. Conrad. 1998. Influence of O2 availability on NO and N2O release by nitrification and denitrification in soils. Global Change Biology 4:387-396.
- Bollmann, A. & H.J. Laanbroek. 2001. Continuous culture enrichments of ammonia-oxidizing bacteria at low ammonium concentrations. FEMS Microbiology Ecology 37:211-221.
- Bollmann, A. & H.J. Laanbroek. 2002. Influence of oxygen partial pressure and salinity on the community composition of the ammonia-oxidizing bacteria in the Schelde estuary. Aquatic Microbial Ecology 28:238-247.
- Bollmann, A., M.-J. Bär-Gilissen, & H.J. Laanbroek. 2002. Growth at low ammonium concentrations and starvation response as potential factors involved in niche differentiation among ammonia-oxidizing bacteria. Applied and Environmental Microbiology 68:4751-4757.
- Bollmann, A., I. Schmidt, A.M. Saunders, & M.H. Nicolaisen. 2005. Influence of starvation on the potential ammonia-oxidizing activity and amoA mRNA of Nitrosospira briensis. Applied and Environmental Microbiology 71:95-102.
- Bollmann, A., K. Lewis, & S. Epstein. 2007. Incubation of environmental samples in a diffusion chamber increases the diversity of recovered isolates. Applied and Environmental Microbiology 73:6386-6390.
Faculty: Bollmann