Continuous cultivation and thermodynamic aspects of niche definition in the nitrogen cycle

The study of model organisms in pure culture has provided detailed information about the physiology and biochemistry of nitrification and related processes. Metagenomic sequencing of environmental samples is providing information to what extent this understanding also applies to natural microbial communities. Here, we outline a conceptual and experimental strategy that links these two approaches. It consists of the mathematical modeling of nitrification and related processes. The model predictions are subsequently validated experimentally by the study of natural microbial communities in continuous cultures under precisely defined environmental conditions. Combined with calorimetry and metagenomic monitoring this form of "experimental metagenomics" enables the answering of current questions in the ecology of the nitrogen cycle.