An international group of scientists recently discovered the first famous organella capable of fixing nitrogen inside a eukaryotic cell, marking the fourth case of primary endosymbiosis in history. This groundbreaking discovery involved the absorption of a prokaryotic cell by a eukaryotic cell and its transformation into an organella.
Known as “Nitroplast,” this new organella was the result of years of research and a stroke of luck. In 1998, Jonathan Church, a professor of naval sciences at the University of California in Santa Cruz, found DNA from an unknown nitrogen-fixing cyanobacteria, UCYN-A, in Pacific waters. This finding triggered further investigation into the unique symbiosis between UCYN-A and seaweed, the bacteria’s host.
Research revealed that UCYN-A and the algae-hosts synchronized their metabolisms, resulting in UCYN-A acquiring organell-like properties. This was confirmed using soft x-ray tomography technology developed by Caroline Larabell at the National Center for X-ray Tomography in the Berkeley Laboratory.
The deepening relationship between UCYN-A and its host led to UCYN-A relying on proteins produced by the host cell, a key indicator of the transformation from endosymbiont to a fully-fledged organella. These changes, including genome reduction and host dependence, are characteristic of organelles like mitochondria and chloroplasts.
The discovery of nitroplast not only challenges existing notions of cell evolution but also has significant implications for ocean ecology and agriculture. Nitroplasts have the ability to break down nitrogen molecules, making it accessible to other organisms crucial for sustaining various ecosystems.
This breakthrough paves the way for incorporating natural nitrogen into agriculture, potentially revolutionizing fertilizer production and reducing carbon emissions associated with current methods. The study received support from the Simons Foundation, the National Institute of General Medicine, and the US Energy Department.