Sapere aude project – Department of Biology - University of Copenhagen

Lasse Riemann > Sapere aude project

Sapere aude project 

Ecology of non-cyanobacterial N2-fixing bacteria in marine waters

Start and duration

1. January 2012, 3 years duration


Lasse Riemann (PI)

Mikkel Bentzon-Tilia (PhD student)

Ina Severin, (PostDoc)

Jeanett Hansen (Technician)

Project summary

The import of nitrogen (N) through biological N2-fixation is essential for plankton productivity in vast areas of the global ocean. In fact, this conversion of N2 gas to ammonium available for growth is fuelling up to ~50% of the new production in some regions. Cyanobacteria are thought to be the main N2-fixing organisms (diazotrophs) in marine waters, but new data show that non-cyanobacterial diazotrophs are also widespread and active. Even though these microbes conceivably influence N and carbon cycling at local, regional and global scales, the knowledge about their ecology is negligible.

Through establishment of the factors regulating nitrogenase gene expression and rates of N2-fixation in indigenous and cultivated non-cyanobacterial diazotrophs, this project will generate a major advancement in our understanding of the ecology and importance of these organisms in marine temperate waters. We will do this in a joint effort with world class experts by combining cutting-edge molecular and ecophysiological approaches. The obtained knowledge will have broad implications for our current understanding of N and carbon cycling in the sea.

Project objective

The objective of the project is to gain insight into the importance and ecology of planktonic non-cyanobacterial diazotrophs through establishment of their environmental loci for active N2-fixation and determination of the factors regulating their activity. This will be done in situ by means of molecular-based examinations of identity and expression of nitrogenase genes, and in vitro by means of experiments linking gene expression and actual N2-fixation rates for indigenous and cultivated heterotrophic bacteria. The unique application of cutting-edge methods within the disciplines of molecular biology and microbial functional ecology will allow for unprecedented insight into the ecology of non-cyanobacterial diazotrophs.

For information about the Sapere aude program of the Danish Agency for Science Technology and Innovation, click here.