Roseobacter with algae. Photo: https://wordsinmocean.com

Roseobacter with algae. Photo: https://wordsinmocean.com

Andy Coghlan reports in New Scientist.com about research that shows how Roseobacter, a type of marine bacteria, tends algae using “pesticides” to keep other microbes away.

Understanding how Roseobacter does this could help us better understand nutrient circulation in the world’s oceans, where the bacteria and their microalgae “crops” are abundant. “They’re key players in global nutrient recycling,” says Eva Sonnenschein of the Technical University of Denmark in Lyngby, who reported her team’s latest results last month at the annual meeting of the American Society for Microbiology in Boston.

Eva C. Sonnenschein is a postdoctoral fellow at the Technical University of Denmark

Eva C. Sonnenschein is a postdoctoral fellow at the Technical University of Denmark

Dr. Sonnenschein’s work builds on a 2011 discovery by Mohammad Seyedsayamdost, now at Princeton University. He found that in times of plenty, the algae produce nutrients that help Roseobacter microbes thrive. In return, the bacteria make antibiotics that serve as pesticides, protecting the algae from rival bacterial strains.

Both the bacteria and the algae appear to benefit from the arrangement, not unlike ants farming aphids. “I suspect it’s mutualism,” says Rita Colwell of the University of Maryland at College Park. “They wouldn’t be there if it wasn’t beneficial to both parties.”

When times get tougher, though, and the algae begin competing with the bacteria for resources, the “farmers” stop making antibiotics and instead produce a substance that kills off the algae, harvesting the rich algal decay products.

Dr. Sonnenschein’s team has now investigated the “tools” that the bacteria use to manage their algal gardens. These include a “herbicide,” tropodithietic acid (TDA), which protects the algae from other bacteria, and roseobacticides, the substances that kill off the algae for harvest.

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