Achi news desk-
The fascinating human gut bacterium Ruminococcus bromii is one of the ten most common bacterial species found in the colon.
This bacterium, first discovered in 1972, plays a unique role in helping to break down resistant starch. These are some of the most commonly eaten carbohydrates in our diet, found in foods such as cereal grains, beans, pulses and some fruit (including plantains and green bananas). Without hard work R bromiicells and other bacterial species in our gut may not have the energy they need to function.
There are many different Ruminococcus species. All are very good at breaking down different complex carbohydrates, mainly thanks to their specialized enzyme systems that allow them to extract energy from dietary fibres. For example, Ruminococcus yellow faces, commonly found in cattle, goats and sheep, is particularly good at degrading cellulose (the main component of plant cell walls). In the human gut, Ruminococcus bromii is the species of bacteria that acts as this specialized starch degrader.
When R bromii breaks down resistant starch in the colon, it forms molecules called short chain fatty acids. There are three main types of short chain fatty acids: acetate, propionate and butyrate. These all have different roles when it comes to our health. Butyrate, for example, is the main source of energy for the cells that line the colon.
Each person has their own distinctive microbiome, which consists of a few hundred different bacterial species. Your microbiome changes throughout your life, depending on many factors – including what medicines you take and the types of foods you eat. Some people will have higher levels of R bromii than others and this could have implications for their health.
A study carried out by myself and colleagues at the University of Aberdeen found that R bromii was most responsive when participants ate diets high in resistant starch. This response happened quickly, within a few days of the diet change. There is plenty of R bromii increased significantly and was also quickly reversed by switching to another diet such as a low-carb diet.
A small number of participants had very low levels of R bombs to begin with. But even when they were fed diets high in resistant starch, population R bromii in their gut stay low. These same volunteers failed to completely break down the resistant starch they were consuming, with much of the starch remaining in their stool samples.
This provided good evidence Ruminococcus bromii plays a central role in the breakdown of starch that is resistant to by-products, such as glucose and acetate, that can be used by other bacteria. These by-products can then be used by other bacteria for growth. For example, acetate can be used to form butyrate.
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This can mean people with low levels of R bromii unable to break down starch efficiently and will produce less beneficial short chain fatty acids.
Carb love
Ruminococcus bromiithe enzyme systems of the cell determine a remarkable ability to degrade resistant starch. R bromii has about 27 enzymes that degrade carbohydrates.
R bromii organizes these enzymes into specialized structures called amylososomes on the cell surface. These structures break down the complex resistant starch into simpler sugars (such as glucose) which the bacterium can then use to grow. R bromii also need vitamins supplied by other species of gut bacteria in order to thrive.
The bacterium breaks down resistant starch through the fermentation process. This process leads to the formation of other acids, such as acetate and formate. This bacterium also forms alcohol (ethanol). “Bromii” actually translates to “alcohol god”, referring to his alcohol producing abilities. The acids produced through the fermentation process can be used to feed other species of bacteria.
For example, the bacterial species can use formate wet to form acetate. This in turn is used to fuel the bacterial species Facalibacterium, which forms butyrate. Butyrate not only provides energy for the cells lining the colon, it also reduces the colonization of pathogens in our gut – helping to support our immune system and reduce inflammation.
Although we don’t think much about what happens to the starchy carbohydrates we eat, you can rest assured that Ruminococcus bromii works hard in your gut, using these foods to nurture other important bacteria in the gut through the acids it forms. These are then used to form a range of other by-products (such as butyrate) which help fuel a healthy colon and even prevent diseases such as cancer.
This article is part of Meet Your Gut Microbes, a series about the rich constellation of bacteria, viruses, archaea and fungi that live in people’s digestive tracts. Scientists are increasingly realizing their importance in shaping our health – both physically and mentally. Each week we’ll look at a different microbe and bring you the latest research on them.
