PNAS Cozzarelli Prize 2021 for paper on bacterial cooperation

The award in the Biomedical Science category goes to Pierre Stallforth's team

The microscope image shows an amoeba killed by the bacteria. Source: Ruchira Mukherji / Leibniz-HKI

Bacteria can defend themselves against predators by cooperating with each other. The team from Paleobiotechnology was able to show this for bacterial Pseudomonas and Paenibacillus species. Individually, they are eaten by amoebae. Together, however, they produce a substance that is toxic to the amoebae. For their work, the team was awarded this year's Cozzarelli Prize by the U.S. journal Proceedings of the National Academy of Sciences (PNAS) in the Biomedical Sciences category.

The annual Cozzarelli Prize acknowledges papers published in the journal PNAS that reflect scientific excellence and originality. The award was established in 2005 as the Paper of the Year Prize and was renamed in 2007 to honor late PNAS Editor-in-Chief Nicholas R. Cozzarelli. Prizes were awarded in a total of six categories for publications in 2021.

Pierre Stallforth's team addressed a defensive alliance of two bacterial species against amoebae. "When Pseudomonas and Paenibacillus join forces, they can successfully defend themselves and even defeat their predator," says Stallforth. In the process, Pseudomonas forms the lipopeptide syringafactin, which in turn is cleaved by peptidases from Paenibacillus. "By jointly producing a chemical weapon, the bacteria escape their fate of being eaten. We think we have discovered just one of many examples of this cooperative strategy," Stallforth explains.

In their habitats, microorganisms rarely occur as isolated monocultures; they usually interact in a gregarious manner with a variety of other species. Secreted small molecules, known as natural products, often play a crucial role in these microbial interactions. They are also an important source for the development of antibiotics, anticancer agents, immunomodulators, and other drugs.

However, identifying new natural products or exploring their ecological roles in a laboratory setting is mostly based on microbial monocultures - even though many compounds are produced only in a polymicrobial environment when needed.

To make their findings, the researchers first exposed 58 strains of bacteria isolated from soil to the amoebae, individually and in combination - finding 11 species that were eaten individually but could jointly defend themselves against the amoebae. "The simplicity of the question is something we like. It's something I think is sometimes underestimated in research," Pierre Stallforth says.


Somak Chowdhury
Ruchira Mukherji
Lisa Reimer
Pierre Stallforth
Shuaibing Zhang