The discovery of an unprecedented cooperation of two marine bacteria to create a vitamin

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Microscopic image of a coculture of the two strains of bacteria. The blue dots represent bacteria, the red dots represent viruses. WIENHAUSEN ET AL./NATURE

A single drop of seawater is home to millions of microbes that coexist, compete… or cooperate. This was demonstrated by a group of German-American researchers from the University of Oldenburg in Lower Saxony. Their study reveals how cooperation between two marine bacteria allows them to produce vitamin B12.

This vitamin, present in meat, milk and fish, is essential for our body. But we are not alone in this: other animals, as well as bacteria and most algae, also desperately need it. Despite its vital importance, the synthesis of vitamin B12 remains the prerogative of a minority of bacteria, estimated at less than a third of all bacterial species.

This was without the discovery of other production workshops, if we are to believe an article which earned Professor Meinhard Simon’s team a publication in the scientific journal Nature, May 8. This study demonstrates that two bacteria, incapable of producing the vital vitamin alone, succeed when they team up.

Exchange of the missing part

It was in the cold waters of the North Sea that researchers from the University of Oldenburg found the bacteria in question. From seawater samples taken near the coast of the German archipelago of Heligoland (Schleswig-Holstein), scientists isolated no less than 144 bacterial strains. Cultivated individually, some of them demonstrated the ability to synthesize part of the vitamin, but none succeeded in producing the complete molecule. However, when cultured together, two bacterial strains of the genera Roseovarius And Colwellia created a surprise.

“We were able to demonstrate that, when these two bacteria grow side by side, they exchange the part they are missing, which allows them to produce vitamin B12 together. It’s totally new! »enthuses Meinhard Simon.

And this cooperation does not only benefit the two partner bacteria: once assembled, the precious molecule is released into the surrounding waters. “This allows other organisms, such as phytoplankton, to grow”continues the German researcher. “This is all the more important as we know that half of the species of marine algae cannot survive without vitamin B12! »

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According to the study, this association between Roseovarius And Colwellia to produce the vitamin is not “very likely not an isolated case”. “Bacteria that can only produce part of the molecule can be found all along the Atlantic Ocean, not just in the North Sea. I’m pretty sure that this type of cooperation exists even in very different ecosystems, in our intestinal microbiota, for example”agrees Meinhard Simon.

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