Seminar of the Insitute of Microbiology

Rhizobia-diatom symbiosis fixes missing nitrogen in the ocean

Bernhard J. Tschitschko – Postdoc - UIBK 

28.11.2024, 11:00 - Hybrid

  • Join online
  • or in presence: Seminarraum Biologie - Foyer (Technikerstraße 25, EG)

 

Abstract

Bernhard J. Tschitschko

Nitrogen (N2) fixation in oligotrophic surface waters is the main source of new nitrogen (N) to the ocean and plays a key role in fueling the biological carbon pump. Oceanic N2 fixation is almost exclusively attributed to cyanobacteria, even though genes encoding nitrogenase, the enzyme fixing N2 into ammonia, are widespread among marine bacteria and archaea. Little is known about these non-cyanobacterial N2-fixers and direct proof that they can fix N in the ocean is missing. In this talk I will report the discovery of a non-cyanobacterial N2-fixing symbiont, Candidatus Tectiglobus diatomicola, which provides its diatom host with fixed-N in return for photosynthetic carbon. The N2-fixing symbiont belongs to the order Rhizobiales and its association with a unicellular diatom expands the known hosts for this order beyond the well-known N2-fixing rhizobia-legume symbioses on land. Our results show that the rhizobia-diatom symbiosis can contribute as much fixed-N as cyanobacterial N2-fixers in the tropical North Atlantic, and that they may be responsible for N2 fixation in the vast regions of the ocean where cyanobacteria are too rare to account for the measured rates.

Nach oben scrollen