An international team of scientists has discovered a new intestinal microbe that feeds exclusively on taurine and produces the foul-smelling gas hydrogen sulphide – Taurinivorans muris.
The gut microbiome mediates our health in a myriad of ways and one of those is by contributing to the levels of hydrogen sulphide – the toxic gas responsible for awful farts – which is essential for several physiological processes and can even protect against pathogens.
Hydrogen sulphide-producing microbes in the gut help “choke out” oxygen-dependent pathogens such as Klebsiella and Salmonella, making it harder for them to colonize.
However, excessive levels can have negative consequences and have been associated with gut inflammation and damage to the intestinal lining, and discovering the key players and processes that produce this noxious gas in our gut is a fundamental first step on the road to developing therapeutic interventions, for example, for inflammatory bowel disease.
Lead author and microbiologist, Professor Alexander Loy from the University of Vienna, explained that just like hydrogen sulphide, taurine has been implicated in a smorgasbord of physiological processes.
“Recent studies have found a link between taurine and healthy ageing – it seems this nutrient may stave away age-related disease,” he said.
“Taurine is a semi-essential amino acid, which we synthesize in small amounts in our liver. However, we get most of our taurine from our diets – especially meat, dairy, and seafood – and it is also one of the most important sources of hydrogen sulphide production in the gut.”
Taurine contributes to various processes in the body, such as bile processing and the balancing of fluids, with some studies revealing that taurine may also have cardiovascular health benefits, but overall, it plays a role in supporting cellular energy levels.
“In addition, taurine is extremely effective in the treatment of the mitochondrial disease, mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), and offers a new approach for the treatment of metabolic diseases, such as diabetes, and inflammatory diseases, such as arthritis,” Professor Loy said.
“Taurine has also been implicated in the regulation of antioxidation, energy metabolism, gene expression, ER stress, neuromodulation, quality control and calcium homeostasis, and these findings have provided impetus for the use of taurine in infant formula, nutritional supplements, and energy drinks, as well as stimulating research into its potential therapeutic uses.
“Considering these findings, the discovery of a new gut microbe that feeds exclusively on taurine (aptly named Taurinivorans muris) is another piece of an exciting puzzle.”
Protection against bacterial pathogens is one of the most important symbiotic functions that the diverse intestinal microbiota confers to its host with the competition for nutrient absorption among the many indigenous microorganisms an ecological foundation of this protective effect.
“However, sulfidogenic bacteria, which either metabolize organic sulphur compounds (e.g., cysteine) or anaerobically respire organic (e.g., taurine) or inorganic (e.g., sulphate, sulphite, tetrathionate) sulphur compounds in the gut, have a higher H2S-producing capacity and are thus potentially harmful to their hosts,” Professor Loy explained.
“Indeed, the abundance and activity of sulfidogenic gut bacteria were associated with intestinal diseases such as inflammatory bowel disease and colon cancer in various studies and many gut pathogens, such as Salmonella enterica and Clostridioides difficile, are also sulfidogenic.”
The bacterium Bilophila wadsworthia is the most prominent taurine-utilizing bacterium in the human gut and diets that contain high quantities of meat, dairy products, or fats can be associated with its proliferation in the gut, as the consumption of high-fat food triggers taurine-conjugated bile acid production and increases the taurine/ glycine ratio in the bile acid pool.
“The new bacterium we described also has a rather unbalanced diet, as it too specializes in consuming taurine,” Professor Loy explained.
“To access sufficient taurine in the gut, however, Taurinivorans muris needs the help of other gut microbes to release it from bile acids. Taurine-containing bile acids are produced in the liver and are increasingly released into the intestine during a high-fat diet to help our body digest fats, and the activities of the bacteria in the intestine in turn influence the bile acid metabolism in the liver.
“H2S can enhance resistance against enteropathogens by directly inhibiting enzymes in aerobically respiring Klebsiella pneumoniae, and while the protective mechanism of T. muris against pathogens may be via hydrogen sulphide, essentially, it is not yet fully understood.
“T. muris could further impact microbial interactions and intestinal metabolism by stimulating the transcriptional activity of prophages that encode auxiliary metabolic genes, such as those involved in sulphur metabolism.
“By isolating the first taurine degrader in the mouse gut, we’re one step closer to understanding how these gut microbes’ mediate animal and human health.”