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Add as preferred source Bacteria, too, depend on good neighborly relations: A new study by the Osnabrück University, in collaboration with researchers from the University of Cambridge in England, shows that soil bacteria live in beneficial communities and frequently exchange nutrients with one another. The study, led by Prof. Dr. Christian Kost, has now been published in the journal Nature Microbiology .
The study examined the prevalence of bacteria that have lost, in the course of evolution, the ability to produce certain substances necessary for their growth. To survive, these so-called "auxotrophic" bacteria rely on nutrients supplied by other bacteria that release them into the environment. Among experts, this hypothesis is known as the "Black Queen hypothesis." Whether and how frequently such auxotrophic bacteria occur in natural bacterial communities—and to what extent they can survive through exchanges with other bacteria—had been insufficiently investigated.
A new study by the research team led by Dr. Christian Kost, a professor of ecology at Osnabrück University, now provides new evidence. "We collected soil samples in Jena, Thuringia, and isolated nearly 7,000 bacterial strains from 27 bacterial communities," Kost explains. "In the lab, we then investigated which bacteria were capable of producing certain nutrients on their own and which relied on nutrient uptake from the environment."
The results: About half of all bacteria in a bacterial community were unable to produce amino acids on their own or could produce only certain ones. Amino acids are essential for protein synthesis and are therefore a vital nutrient. In further experiments, the research team showed that isolated auxotrophic bacteria in mixed cultures with other bacterial strains were supplied with these nutrients and that their growth depended on such a supply.
A subsequent genetic analysis suggested that an accumulation of mobile DNA segments might explain the origin of the observed auxotrophies. These mobile elements are known to switch off genes and could thus disrupt the independent production of amino acids in bacteria.
"Overall, our investigations support the Black Queen hypothesis and show that soil bacteria do not merely compete for nutrients. Instead, they coexist in a kind of network in which they supply each other with nutrients, thereby enabling their survival in the first place," Kost said. Furthermore, the results provided an additional explanation for why isolated bacterial strains are often difficult to culture under laboratory conditions.
"This study offers new insights into how bacteria coexist with one another in their natural environment. The findings can also help us better understand bacterial communities that play an important role in biomedicine or agriculture."
Ghada Yousif et al, Obligate cross-feeding of metabolites is common in soil microbial communities, Nature Microbiology (2026). DOI: 10.1038/s41564-026-02457-6
Journal information: Nature Microbiology
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