Nav: Home

Two-faced bacteria

March 05, 2020

The gut microbiome, which is a collection of numerous beneficial bacteria species, is key to our overall well-being and good health. Recent studies have linked the gut microbiome with several beneficial properties, such as aiding in the development of our immune system and warding off pathogen infections.

Many deadly pathogens are motile, meaning they can move spontaneously, and their ability to infect is based on their response to different environmental cues. Major cues for the pathogens are the molecules (or metabolites) produced in the gut. Pathogens interpret distinctive metabolites differently and are either attracted or repelled by them (i.e., migrate toward or away from them).

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, assistant professor, and Dr. Arul Jayaraman, professor, in the Artie McFerrin Department of Chemical Engineering at Texas A&M University, this fact 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, a research team including Lele, Jayaraman and Dr. Michael Manson from the Department of Biology at Texas A&M, studied the response of the beneficial gut bacteria, E. coli to indole. In an article in the Proceedings of the National Academy of Sciences, the researchers describe the discovery of a previously unknown response to indole, in which 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 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," said Jayaraman. "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."

Since the bacteria that produce indole in the gut typically are enmeshed in mucus layers among other bacteria, the indole concentration drops as one gets further away from the source of indole. Since pathogens tend to pass through the gut relatively far from the bacteria that produce indole, they are not likely to encounter high concentrations of indole for a sustained period. Therefore, they are not sensitized to indole, and any indole they encounter repels them.

Studies continue to show that it is important to have a diverse mix of beneficial bacteria in the gut. According to Lele, this research is a step toward understanding how the gut microbiome might change with time. "The key question is, 'How do different species of bacteria colonize specific niches?' We have addressed a part of that question," said Lele. "The next step is to examine the response of multiple species of bacteria to a mix of different metabolites that are found in the gut."
-end-


Texas A&M University

Related Immune System Articles:

Too much salt weakens the immune system
A high-salt diet is not only bad for one's blood pressure, but also for the immune system.
Parkinson's and the immune system
Mutations in the Parkin gene are a common cause of hereditary forms of Parkinson's disease.
How an immune system regulator shifts the balance of immune cells
Researchers have provided new insight on the role of cyclic AMP (cAMP) in regulating the immune response.
Immune system upgrade
Theoretically, our immune system could detect and kill cancer cells.
Using the immune system as a defence against cancer
Research published today in the British Journal of Cancer has found that a naturally occurring molecule and a component of the immune system that can successfully target and kill cancer cells, can also encourage immunity against cancer resurgence.
First impressions go a long way in the immune system
An algorithm that predicts the immune response to a pathogen could lead to early diagnosis for such diseases as tuberculosis
Filming how our immune system kill bacteria
To kill bacteria in the blood, our immune system relies on nanomachines that can open deadly holes in their targets.
Putting the break on our immune system's response
Researchers have discovered how a tiny molecule known as miR-132 acts as a 'handbrake' on our immune system -- helping us fight infection.
Decoding the human immune system
For the first time ever, researchers are comprehensively sequencing the human immune system, which is billions of times larger than the human genome.
Masterswitch discovered in body's immune system
Scientists have discovered a critical part of the body's immune system with potentially major implications for the treatment of some of the most devastating diseases affecting humans.
More Immune System News and Immune System Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.