German researchers study cooperative evolution in bacteria to learn how organisms help each other

Organisms will cooperate to be more "fit" and stand a better chance of surviving, researchers in Germany said in a study released earlier this month.

The study, "Reciprocal Fitness Feedbacks Promote the Evolution of Mutualistic Cooperation," describes mutually beneficial interactions as "ubiquitous in nature and highly diverse in form and function."

"By providing organisms with new phenotypic traits, mutualistic interactions represent an important source of evolutionary innovation that has been key to the diversification of life on Earth," the report's introduction said. "Because of their ability to produce a broad range of different metabolites, bacteria are frequently involved in mutualistic interactions with both other bacteria and eukaryotic hosts."

Researchers in the study observed generations of bacteria to document evidence of evolving mutual cooperation. The researchers initially observed that two bacterial strains would grow only when the strains shared essential amino acids. As the study progressed, the researchers observed instances of actual cooperation in the form of increased amino acids shared between the two strains.

"Here, we use an experimental evolution approach to test whether cooperation evolves between two synergistic bacterial genotypes and if so, which evolutionary mechanism can explain its emergence," the report said.

Researchers co-cultured pairs of the bacterium Escherichia coli, which can grow only when they reciprocally exchange essential amino acids.

"Thus the interaction was initially based on a trading of byproducts that were not produced to benefit the corresponding partner," the report said. "Given that nutrient-starved bacterial genotypes frequently aggregate to enhance metabolic exchange, we hypothesized that the resulting spatial structures should also facilitate the evolution of metabolic cooperation."

In their conclusions, the researchers found that they could identify "positive fitness feedbacks" in the studied bacteria that drove their cooperation the study said.

"These results suggest the evolution of mutualistic cooperation is less challenging than previously thought," the report said.

Authors in the study were Daniel Preuger with Experimental Ecology and Evolution Research Groupat the Max Planck Institute for Chemical Ecology in Jena, German and Samir Giri, Linea K. Muhsal and Leonardo Ona, all with the department of ecology school of biology/chemistry at the University of Osnabrück in Germany, and  Christian Kost, who is head of the ecology department at the the University of Osnabrück.