'Fairy Rings' Appear in Antarctic Moss Beds... The Secret of Bacteria That Help Plants Grow [Reading Science]

Beneficial bacteria account for 58.2% inside rings... four times the share in ordinary moss colonies
Korea Polar Research Institute confirms plant-growth-promoting effects... offers clues to vegetation changes in extreme environments

A “fairy ring,” a circular pattern that appears in the barren Antarctic landscape, has been found to provide a habitat for microorganisms that help plants grow. The inner area of the rings contained more than four times as many beneficial bacteria as ordinary moss colonies. The finding is expected to offer clues to how plants take root and ecosystems expand in extreme environments.

The Korea Polar Research Institute said on October 16 that a research team led by Senior Researcher Lee Jeongeun had analyzed fairy rings in moss colonies on Barton Peninsula near the King Sejong Station in Antarctica and found that bacteria that promote plant growth were concentrated there.

Plant growth-promoting microbes isolated from Antarctic fairy rings. (1) Schematic diagram of an Antarctic moss colony; (2) proportions of isolates by moss phenotype; (3) fresh weight results from growth-promotion experiments; and (4) photos of plant growth. Provided by the research team.

A fairy ring is a natural phenomenon in which fungi spread underground, forming a circular ring around plants. The familiar sight of mushrooms growing in a circle is one example, and fairy rings are observed in grasslands and mountains around the world, as well as in Antarctic moss colonies. Interactions among plants, fungi and soil microorganisms occur as the rings form, changing the surrounding ecological environment.

The research team compared microorganisms found inside fairy rings, along their boundaries and in ordinary moss colonies, focusing on Sanionia uncinata, a moss species that grows in Antarctica. The results showed that bacteria such as Sphingomonas and Rhizobium, which benefit plant growth, increased in concentration in the fairy-ring areas.

In particular, bacteria belonging to the order Sphingomonadales accounted for an average of 58.2% of the microbial communities inside the fairy rings. This was about 4.1 times the 14.1% found in ordinary moss colonies.

The team also isolated bacteria directly from the fairy rings and tested their effects on plant growth. The isolated bacteria produced auxin, a hormone that promotes plant growth, and were able to convert soil phosphate into a form that plants can absorb more easily. They were also found to secrete siderophores, substances that help plants absorb iron.

When the bacteria were applied to Arabidopsis, a plant used in experiments, the plants’ overall weight increased and root development was promoted. This confirmed that the bacteria found in fairy rings may do more than simply occur in large numbers in a particular area: they can also help plants grow.

The researchers noted that interactions among plants, fungi and bacteria in fairy rings may create conditions favorable for new plants to become established. They said microorganisms could play an important role in “vegetation succession,” the process in which existing vegetation changes and new plants take hold. However, the growth-promoting effects were confirmed in laboratory tests on Arabidopsis, and further research is needed to determine whether the bacteria actually help new plants become established in Antarctica.

“We found that beneficial bacteria that help plants grow are more abundant inside fairy rings formed by plants and fungi together,” said Lee Jeongeun, a senior researcher at the Korea Polar Research Institute. “This could provide important clues to understanding how plants take root and ecosystems expand in extreme environments.”

The findings were published in the international journal BMC Plant Biology.

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