Related Experiment Video
Updated: Jun 28, 2025

Generation of Marked and Markerless Mutants in Model Cyanobacterial Species
Published on: May 29, 2016
Nitrogen-fixing organelle in a marine alga
Tyler H Coale1, Valentina Loconte2,3, Kendra A Turk-Kubo1
1Ocean Sciences Department, University of California, Santa Cruz, CA, USA.
Abstract:
Symbiotic interactions were key to the evolution of chloroplast and mitochondria organelles, which mediate carbon and energy metabolism in eukaryotes. Biological nitrogen fixation, the reduction of abundant atmospheric nitrogen gas (N2) to biologically available ammonia, is a key metabolic process performed exclusively by prokaryotes. Candidatus Atelocyanobacterium thalassa, or UCYN-A, is a metabolically streamlined N2-fixing cyanobacterium previously reported to be an endosymbiont of a marine unicellular alga. Here we show that UCYN-A has been tightly integrated into algal cell architecture and organellar division and that it imports proteins encoded by the algal genome. These are characteristics of organelles and show that UCYN-A has evolved beyond endosymbiosis and functions as an early evolutionary stage N2-fixing organelle, or "nitroplast."
Related Concept Videos
The Anatomy of Chloroplasts
Structure of...
Anatomy of Chloroplasts
Overview of Nitrogen Metabolism
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this...
The Calvin Benson Cycle
The Roles of Bacteria and Fungi in Plant Nutrition
The Nitrogen Cycle

