Scientists have recently observed a rare evolutionary event that occurs only once in a billion years: the merging of two forms of life into one organism with unique abilities. This phenomenon, known as Primary endosymbiosis, occurs when one microorganism absorbs another and begins to use it as an internal organ. In return, the host provides the symbiont with nutrients, energy, and protection. Over time, the symbiont becomes essential for the survival of the host.
X-ray images of Braarudosphaera Bigelowii at different stages of cell division revealed the newly acquired nitroplast (highlighted in blue), algae core (blue), mitochondria (green), and chloroplasts (purple).
A similar event took place around 2.2 billion years ago when Archaea absorbed a bacterium that later became mitochondria, laying the groundwork for the evolution of complex life forms. The second instance occurred approximately 1.6 billion years ago, when complex cells engulfed cyanobacteria that became chloroplasts, enabling plants to harness solar energy.
In a recent discovery, scientists found a new instance of symbiosis in Braarudosphaera Bigelowii algae, which absorbed cyanobacteria allowing them to fix atmospheric nitrogen. This finding suggests the emergence of a new organelle, referred to as “nitroplast,” which began developing around 100 million years ago and could enhance plant growth.
Evidence supporting this discovery includes synchronized cell division between the host and symbiont, as well as changes in the protein composition of bacteria, which now rely on algae for essential proteins. Further research is ongoing, as scientists aim to uncover more about nitroplasts and their impact on other cells. The study detailing these findings was published in the journal Cell.