Hydrogen-consuming microbes may solve intestinal problems. Photo Shutterstock. Microbiologist Taojun Wang dived into the smelly business of hydrogenotrophic microbes – the bacteria and archaea that consume hydrogen – in our gut. This unfamiliar group may help understand intestinal disorders and diseases, such as irritable bowel syndrome, obesity, and constipation.
It is no secret, even though we sometimes wish it was: our gut produces gases. No doubt you are familiar of the smelly hydrogen sulphide and odourless methane. But did you know that the gut also produces a lot of hydrogen from microbial fermentation? An excess of this gas can in turn slow down fermentation – which is not good because fermentation gives us nutrients from dietary fibres and helps keeping us healthy. Taojun Wang (Laboratory of Microbiology) set out to survey a group of special gut microorganisms that use hydrogen as an energy source.
Exhaling hydrogen
Patients suffering from irritable bowel syndrome (IBS) often have a distorted hydrogen metabolism. Their breath contains more hydrogen than that of healthy people. ‘The high hydrogen concentration can be associated with abdominal pain that IBS patients experience,’ Wang says. In addition, the hydrogenotrophic microbes are linked to other symptoms: high levels of methane or of its producers (methanogens), are associated with longer gut transit time and constipation; another group, the sulphate reducing bacteria, is associated with pain signals in the gut.
No competition
Together with the reductive acetogens, the methanogens and sulphate-reducers make the three main groups of hydrogenotrophic microbes in the human gut. Simply put, the first group produces acetic acid, the second methane, and the third hydrogen sulphide. The methanogens use hydrogen as their essential energy source, the others have alternatives.
Wang studied a representative of each group in vitro, under conditions that simulated the human gut environment. Surprisingly, the three species were better off together than alone. ‘It shows that they do not compete for hydrogen, unlike we expected,’ he says. Instead, the early growth of the methanogen was faster when the other two were present.
Diversity
A diverse community of gut microbes (gut microbiota) is generally a sign of good health. IBS patients tend to have lower levels of bifidobacteria that are considered beneficial. Wang found a link between diversity and the level of methanogens in the gut: the more methanogens, the higher the diversity.
In a follow-up experiment, he added methanogens to faecal samples that cannot produce methane. The faecal microbiota with the added microbes started to produce methane, proving that these methanogens can establish and be active in a complex community. In vivo experiments would be required to test whether such an addition increases diversity of the intestinal microbiota. Wang reckons the hydrogenotrophic microbes could provide an interesting direction for future treatment of IBS, because the hydrogen metabolism is linked to the symptoms.
