This is the first fungus known to host complex algae inside its cells

It’s unclear if the newly discovered alliance exists in the wild

marine symbiosis

FUNGAL INSIDER  In a first, scientists have discovered that the marine algal species Nannochloropsis oceanica (green round cells) can live inside the fungus Mortierella elongata (long transparent tubes). The species formed a mutually beneficial relationship in a lab dish.    

Z.-Y. Du et al/eLife 2019 (CC BY 4.0)

A soil fungus and a marine alga have formed a beautiful friendship.

In a lab dish, scientists grew the fungus Mortierella elongata with a photosynthetic alga called Nannochloropsis oceanica. This odd couple formed a mutually beneficial team that kept each other going when nutrients such as carbon and nitrogen were scarce, researchers report July 16 in eLife.

Surprisingly, after about a month together, the partners got even cozier. Algal cells began growing inside the fungi’s super long cells called hyphae — the first time that scientists have identified a fungus that can harbor eukaryotic algae inside itself. (In eukaryotic cells, DNA is stored in the nucleus.) In lichens, a symbiotic pairing of fungi and algae, the algae remain outside of the fungal cells. 

In the new study, biochemist Zhi-Yan Du of Michigan State University in East Lansing and his colleagues used heavy forms of carbon and nitrogen to trace the organisms’ nutrient exchange. The fungi passed more than twice as much nitrogen to their algal partners as the algae sent to the fungi, the team found. And while both partners lent each other carbon, the algal cells had to touch the fungi’s hyphae cells to make their carbon deliveries.

It’s unclear if the newly discovered alliance exists in the wild. But both N. oceanica and M. elongata are found around the world, and could interact in places such as tidal zones. Learning more about how the duo teams up may shed light on how symbiotic partnerships evolve.

algal and fungal cells
IN TOUCH Algal cells (green) had to make contact with long fungal cells called hyphae (brown tubes) in order to share carbon. The algae may pump nutrients through filaments that connect them to the fungal cells. Z.-Y. Du, colored by Igor Houwat

Tina Hesman Saey is the senior staff writer and reports on molecular biology. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master’s degree in science journalism from Boston University.

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