Studies of microbial interactions help us understand soil nitrogen turnover

Sara Hallin wants to challenge our current knowledge of microbes in the nitrogen cycle and understand the mechanisms that determine the fate of nitrogen in soils. Microbes determine the amount of plant-available nitrogen that remain in the soil and the amount that is lost to air and water as gaseous and water soluble nitrogen.

Nitrogen is an important nutrient for all organisms and typically limits growth in ecosystems. At the same time, there can be too much nitrogen, which leads to eutrophication and threats to biodiversity. The climate is also affected by nitrogen through emissions of nitrous oxide, a powerful greenhouse gas that is largely produced by soil microbes.

The global nitrogen cycle is driven by microbes

Microbes convert nitrogen from one form to another. Sara Hallin's research has shown that many microbes seem to be specialized in carrying out a certain reaction in the nitrogen cycle. This means that several specialists must work together to carry out the processes, which usually includes several steps.

“My research program challenges our current understanding of the nitrogen cycle by taking into account interactions and competition between specialized microbes. We will also open new lines of research on unknown organisms and processes,” says Sara Hallin

Sara Hallin and her research group will map the networks of interacting microbes that convert specific forms of nitrogen in different soil ecosystems to reconstruct the nitrogen cycle. This will be done by analyzing large amounts of DNA sequences from soil ecosystems all over the world. This is followed by experiments to decipher how soil properties and the interaction of nitrogen-cycling microbes shape these networks. In parallel, they will seek evidence for theoretically possible processes and then hopefully isolate the microbes involved.

The new knowledge can help in reducing emissions of nitrous oxide and increase nitrogen utilization in agricultural soils. The research results can also be important for the understanding of carbon cycling, for example sequestering of carbon in soil.