Antibiotics save countless lives by fighting off pathogens in the body, however they also kill beneficial bacteria in the body that are necessary for keeping us alive and healthy. A team of scientists in Portugal and Spain may have found a molecule that can help restore beneficial bacteria in the gut.
Quorum sensing is how bacteria interact and coordinate with one another. The scientists showed that by increasing levels of a specific quorom-sensing molecule, autoinducer-2 (AI-2), in the gut, mice that had been given antibiotics were repopulated of beneficial bacteria.
The scientists sequenced the bacteria in fecal samples of mice before and after a 28-day regimen of streptomycin treatment. Prior to antibiotic treatment, bacteria of the Bacteroidetes and Firmicutes phyla made up 48 and 43 percent, respectively, of the bacteria in the gut. After 28 days, diversity in the guy decreased significantly and the Bacteroidetes and Firmicutes ratios shifted to 90% of Bacteroidetes species and Firmicutes species made up only 0.7% of all species.
They then repeated this experiment but also generated E. coli that were mutated and not able to absorb AI-2 and introduced these bacteria into the mice that were treated with antibiotics. They used E. coli because streptomycin increases levels of E. coli in the gut when exposed to it. This resulted in AI-2 levels in the gut to be increased as well as increase of bacteria from the Firmicutes phylum, which had been greatly destroyed by the antibiotic in the previous experiment.
They were able to increase AI-2 levels and therefore beneficial bacteria by introducing bacteria that could not absorb it. AI-2 could also be directly given to individuals who were given antibiotics and the scientists are now working on developing drugs that would release AI-2 only in the gut. However, antibiotics are not the only cause of dysbiosis. Diet and other factors can result in changes to gut bacteria and by introducing this molecule and other molecules that bacteria use to communicate with one another, it may be possible to treat gastrointestinal diseases as well as dysbiosis caused by external factors.