The gut microbiome, which is a collection of numerous beneficial bacteria species, is essential to our overall well-being, good health and warding off pathogen infections.
Major cues for the pathogens are the molecules (or metabolites) produced in the gut.
The metabolite indole is an example of a microbiome-produced small molecule that is abundant in the gut and is a powerful repellent for bacteria.
According to Dr. Pushkar Lele, this led to a simple question: “Why does indole, which is produced by many of our beneficial bacterial species, not repel the good gut bacteria along with the bad ones?”
To answer this question, researchers studied the response of the beneficial gut bacteria, E. coli, to indole. In an article in the Proceedings of the National Academy of Sciences, they describe the discovery of a previously unknown response to indole, where the molecule seems to both repel and attract bacteria. This Janus response — named after the Roman god Janus who had two faces, one looking into the future and one looking into the past — has to do with the way indole is interpreted by the bacterial chemo-receptors.
“We found that there are two receptors in E. coli that sense indole,” Lele said. “One senses indole as a repellent, and one senses indole as an attractant. Sustained exposure to high concentrations of indole desensitizes the receptor that interprets it as a repellent. This leads to indole being sensed only as an attractant.”
According to Dr. Arul Jayaraman, the Janus response displays a large amount of sophistication, and the discovery could lead to a better understanding of the complexities of the gut microbiome.
“Beneficial bacteria aggregate on the surfaces within the gut based on some common feature,” Jayaraman said. “We propose that one such feature is the ability to produce or sense indole. Bacteria that produce indole could group together and be attracted to niches where indole concentrations are high.”
Featured Researchers
Dr. Arul Jayaraman
- Professor; Department Head
- Presidential Impact Fellow
- Holder of the Ray B. Nesbitt Endowed Chair
Dr. Pushkar Lele
- Assistant Professor