报 告 人：Asa Frostegard 教授 Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Norway
联 系 人：张晓君 firstname.lastname@example.org
Denitrifying organisms need to handle frequent fluctuations in oxygen and oxyanion availability. Although being taxonomically diverse, their overall regulatory network of the denitrification pathway seems to be quite general. They prefer oxygen as electron acceptor for respiration, but when it becomes limiting, they express reductases that allow them to sustain a respiratory metabolism and thrive on nitrogen oxyanions. Organisms with a complete denitrification pathway reduce NO3- to N2 in four consecutive steps via the intermediates. Our studies of model bacterial denitrifiers as well as new isolates have unraveled a large phenotypic diversification among these organisms with respect to the way they handle transitions from aerobic respiration to denitrification, leading to large variations in accumulation of the intermediates (NO2-, NO, N2O) even between closely related bacteria. This may be due to lack of genes encoding some of the reductases. Often, however, transcriptional regulation or control mechanisms at the metabolic level are involved. In this talk I will summarize our current knowledge on denitrification phenotypes and discuss how differences in transcriptional regulation and metabolic control influence N2O emissions, and how phenotypes with strong capacity for N2O reduction can be used to mitigate the emissions of this climate gas from agricultural ecosystems.
Asa Frostegard, Together with Prof. Lars Bakken and Dr. Peter Dörsch, I founded the NMBU Nitrogen Group (http://www.nmbu.no/en/research/groups/nitrogen) which now comprises about 25 co-workers. Our main focus is on the regulatory biology of denitrification. Studies include genome analyses and phenotypic characterisations of the eco-physiology of selected microbes, representing different groups of denitrifiers and other nitrate reducing organisms; analyses of gas kinetics of denitrifier communities in response to oxygen depletion and other environmental controllers; and the abundance and diversity of denitrification genes and transcripts in soil. We have strong links to research groups inside Norway (NIBIO) and have established collaboration with a number of renowned research groups in Europe, China, Ethiopia, New Zealand and USA. Our research has received attention both nationally and internationally. In the National Evaluation of biological and medical research in Norway in 2011 our group received the score “Very Good to Excellent”. I recently coordinated a Frimedbio project, financed by Norwegian Research Council, and a Marie Curie Initial
Training Network, NORA (Nitrous Oxide Research Alliance; https://nora.nmbu.no/), financed by EU within the Excellence pillar. A recent (2017) Eurovision documentary about our research: http://www.euronews.com/2017/01/30/no-laughing-matter-nitrous-oxideanother-climate-enemy. We were invited to arrange the 17th European Nitrogen Cycle meeting in Oslo 26-28 September 2012. Recognition by the international research community was also shown when I in 2013 was elected to be one of the ten Members of the International Directory Board of ISME; International Society for Microbial Ecology (http://www.isme-microbes.org/).