When Small Organisms Merge

Three times in Earth’s long history, a process called endosymbiosis has occurred. And it has totally changed life on Earth.

Two billion years ago, all life was single-celled organisms in an oxygen-free environment.

Some of these bacteria-like creatures engulfed others into their cell walls and began a symbiotic relationship called endosymbiosis.

The smaller organisms became organelles within the larger cell—most importantly, the mitochondria—providing energy to the cell in exchange for protection and nourishment.

As oxygen levels rose, these more sophisticated single-cell creatures thrived and would eventually develop into multicellular life-forms.

Six-hundred million years ago, another very important merging occurred.

This time, cells absorbed a bacterium that could perform photosynthesis. It became another organelle, the chloroplast, and with those, the larger organisms evolved into plants.

Today, scientists have discovered a third important endosymbiosis underway. Some algae have engulfed nitrogen-fixing bacteria, which have become a new kind of organelle—a nitroplast.

This allows the algae to secure their own nitrogen, vital for plant function, directly from air. And it could have huge potential in fertilizer research for human agriculture, too.

The mitochondria enabled multicellular life. The chloroplast gave rise to plants. What changes could the nitroplast bring?