This article is taken from Science et Avenir – La recherche n ° 899, dated January 2022.

Contrary to what scientists thought, the association of bacterial and plant species for mutual benefit (symbiosis) is not a privilege of terrestrial plants. A study by biologists from the Max-Planck Institute for Marine Microbiology in Bremen (Germany) showed that Mediterranean sea grasses harbor bacteria in their root tissue that provide them with nitrogen in exchange for sugars. and essential amino acids for them. Development.

About 600,000 km. set a distance² On most coasts of our planet, except for Antarctica, seagrass beds form real meadows of flowering plants in the ocean. These ecosystems, cradles of rich biodiversity, are also essential carbon sinks: they store 1,500 tons of carbon dioxide per hectare, three to seven times more than forests.

bacteria convert nitrogen into nutrients

However, in some parts of the world their prosperity was a mystery. How to explain the existence of seagrass beds in many coastal areas where nitrogen is only available in low concentrations for long seasons? This is the riddle that German researchers have just clarified. bacteria Candidate Rapid-Neptune ,She. c. Neptune) Convert nitrogen dissolved in water and sediment into a form usable by seagrass beds.

Just as nitrogen-fixing microorganisms could favor colonization by the ancestors of earlier land plants, soils poor in this chemical element. She. c. Neptune This probably allowed flowering plants to invade nitrogen-poor marine habitats about 100 million years ago. Scientists believe that such symbiosis may also exist in tropical seagrass beds and salt marshes.