Researchers Discover How Bacteria Can Achieve Its Nutritional Exchange

It's been relatively unclear whether microorganisms exchange metabolites exclusively by releasing them via surrounding environments or if there's a direct connection between cells for this very purpose.

Scientists from the Research Group Experimental Ecology and Evolution at the Max Planck Institute for the Chemical Ecology in Jena, Germany used the soil bacterium acinetobacter baylyi and the gut Escherichia coli by experimentally deleting bacterial genes from the genome of both species. They were able to generate mutants that were no longer able to produce certain amino acids, yet produced increased amounts of others. 

Both bacterial strains were able to cross-feed each other in co-culture by compensating the experimentally induced deficiencies. However, separating the two bacterial strains with a filter allowed free passage of amino acids abolished the growth of both strains.

"This experiment showed that a direct contact between cells was required for the nutrient exchange to occur," said Samay Pande of the Max Planck Institute, in a news release.

Under a microscope, the co-culture further showed formations between bacterial strains that enabled the exchange of nutrients between the cells formed bacterial strains. However, researchers found it particularly interesting that only the gut microbe Escherichia coli was capable of forming these structures and connecting to Acinetobacter bayliyi or other E. coli cells.

"The major difference between both species is certainly that E. coli is able to actively move in liquid media, whereas A. baylyi is immotile. It may thus be possible that swimming is required for E. coli to find suitable partners and connect to them via nanotubes," explains Christian Kost, head of the Research Group Experimental Ecology and Evolution, which is funded by the Volkswagen Foundation.

"A lack of amino acids triggered the formation of nanotubes. Deleting a gene, which is involved in the production of a certain amino acid, caused the resulting bacteria to connect to other bacterial cells and ? in this way ? compensate their nutritional deficiency. However, nanotubes did not form when the required amino acids were supplemented to the growth medium, indicating that the formation of these structures obviously depends on how 'hungry' a cell is," the researchers summarized. "Using bacterial communities as experimentally tractable model systems will help to explain why so many organisms have developed a cooperative lifestyle in the course of their evolution."

More information regarding the findings can be seen via the Max Planck Institute for Chemical Ecology.