Researchers at the Helmholtz Centre for Infection Research in Braunschweig have reported that the effect of a dietary fibre on gut bacteria depends on which other microbes are present. The study was published in Nature Microbiology on 2 October 2026, led by Caroline Tawk, Youssef El Mouali and Till Strowig with colleagues at EMBL Heidelberg and the University of Trento, and funded by the German Research Foundation and the RESIST Cluster of Excellence. The team assembled a defined community of 21 human gut bacteria in the laboratory and tested it against 94 dietary components. More than half of those components promoted the growth of Segatella copri, a bacterium found more often in non-industrialised populations than in industrialised ones. When S. copri competed against Bacteroidaceae on arabinan, a plant carbohydrate, it gained no advantage on its own. "Only when we added Escherichia coli to the mix, the competitive balance shifted in favor of S. copri," said Caroline Tawk, one of the lead authors.
The experiments were done in bacterial culture
The laboratory results were checked against publicly available microbiome data from around 1,000 healthy adults across industrialised and non-industrialised populations, where greater Enterobacteriaceae diversity went alongside a higher proportion of S. copri. That is an association in existing datasets rather than a test in people. The experiments themselves used artificial bacterial communities in culture, and no health outcome was measured. Till Strowig, the senior author, said: "We need to clarify in further studies whether this knowledge can be used for personalized dietary or microbiome approaches."
What this means for your supplement routine
Nothing here changes what a fibre supplement or a probiotics does, because the study tested neither. It reports that the same dietary component can act differently on the same bacterium depending on the rest of the community around it, which is one reason microbiome findings are hard to carry from one person to the next. If the effect of a dietary component depends on the surrounding community, a test that scores one species in isolation is reading less than this result suggests matters. This is early-stage microbiology and it supports no claim about what any product will do in a given person’s gut.
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This article reports published news and research and is for information only. Food supplements are not a substitute for a varied diet or medical care, and no product mentioned is intended to diagnose, treat, cure or prevent any disease. Speak to your GP or pharmacist before changing what you take, especially if you are pregnant, breastfeeding, or taking prescribed medicines.