Bacteroides, found inside intestines, are much more useful than you think.

Bacteria is one of the earliest life forms that appeared on the face of our planet. They come in a number of shapes ranging from rods to spirals. An interesting fact about these microorganisms is that they are present virtually everywhere in this world. Bacteria inhabit water, plants, soil, and go as far as the depth of the Earth’s crust. Given the spread of their habitats, it is simply impossible for the humans to escape their grasp. Consequently, a variety of bacteria are found inside our bodies. A lot of people believe that bacteria only have a parasitic relationship with us but that’s not true. Bacteria like Bifidobacterium Longum, Escherichia Coli, and Bacteroides Thetaiotamicron are extremely useful for a human body.

Similarly, the researchers of the Stanford University have identified the importance of the Bacteroides found inside our intestines. They performed an experiment on mice and observed that a byproduct of the bacteria’s metabolism, Propionate, hinders the growth of one of the most common intestinal pathogen called Salmonella. This amazing discovery will allow the medical professionals to understand why some people fight better against intestinal infections than the others. This will help them in developing better treatment strategies which may lead to some excellent results. Dr. Denise Monack, a Senior Author of the paper who is a Professor of Microbiology and Immunology, mentioned that in the following words:

“Humans differ in their response to exposure to bacterial infections. Some people get infected and some don’t, some get sick and others stay healthy, and some spread the infection while others clear it. It has been a real mystery to understand why we see these differences among people. Our finding may shed some light on this phenomenon.”

Salmonella infections generally last for 4 to 7 days but some of the patients may require hospitalization for their recovery process due to the severity of the illness. The patient experiences fever, abdominal cramps, and diarrhea. Contaminated food is the most common cause of this infection. According to an estimate of the Centers for Disease Control and Prevention, Salmonella affects 1.2 million people out of which 23,000 patients are hospitalized. Nearly 450 people die due to this infection every year. You can imagine the severity of this infection by considering that the facts given above are for the United States, only.

Researchers have been trying to find a possible counter for this deadly infection for years. Earlier, the main focus of the scientists was to examine a series of genes and see how they react to Salmonella. This time around, they decided to have a look at the different responses they get due to the variability of gut bacteria in the mice. It was observed that Propionate doesn’t instigate the immune system to stop the pathogen. Rather, it prolongs the time taken by the Salmonella to start dividing by increasing its internal acidity. Amanda Jacobson, the Lead Author of the study who is a Graduate Student in Microbiology and Immunology, talked about the complexity of the process and said,

“The gut microbiota is an incredibly complex ecosystem. Trillions of bacteria, viruses and fungi form complex interactions with the host and each other in a densely packed, heterogeneous environment. Because of this, it is very difficult to identify the unique molecules from specific bacteria in the gut that are responsible for specific characteristics like resistance to pathogens.”

All these efforts began when scientists discovered that two strains of mice harbor different amounts of Salmonella after being injected with the pathogen. The first step was a fecal transplant which helped them to determine that the natural composition of the bacteria inside intestines has a vital role in the growth of the Salmonella. After that, the researchers took help of machine-learning tools to identify that the Bacteroides made all the difference.

These bacteria produce short chains of fatty acids like Acetate and Propionate. The quantity of Propionate was three times more in the mice that were protected against Salmonella. It decreases the intercellular pH of the Salmonella which increases the time needed by the pathogen to grow. Jacobson described that by saying,

“Collectively, our results show that when concentrations of propionate, which is produced by Bacteroides, in the gut are high, Salmonella are unable to raise their internal pH to facilitate cellular functions required for growth. Of course, we would want to know how translatable this is to humans. The next steps will include determining the basic biology of the small molecule Propionate and how it works on a molecular level.”