Gut Bacteria: Fiber's Complex Relationship Revealed

Recent laboratory studies have unveiled a more complex interplay between plant fiber and gut bacteria than previously understood.

While fiber is known to promote the growth of certain gut microbes, research led by Till Strowig at the Helmholtz Centre for Infection Research suggests this relationship is nuanced. Experiments with communities of gut bacteria grown in the lab revealed that E. coli, a bacterium from the Salmonella family, played a crucial role in helping one of the dominant fiber-eating microbes, Segatella copri, thrive.

This finding challenges the straightforward assumption that diet alone dictates gut bacterial composition. Previously, it was observed that S. copri is more prevalent in non-industrialized populations with plant-rich diets, while Bacteroidaceae dominates in industrialized nations. However, direct dietary changes had not consistently shown a clear link to S. copri abundance.

The new research demonstrated that while a specific fiber, arabinan, was necessary for S. copri's expansion, its success was contingent on the presence of E. coli. Without E. coli, S. copri did not outcompete its rivals, even with arabinan present. This suggests that sugars released from fiber breakdown may act as signaling molecules rather than just a food source for E. coli, influencing the competitive balance within the gut community.

Analysis of human and mouse gut data, along with food microbe samples, supported these findings. People with non-industrialized lifestyles, who consumed more plant-based foods, tended to have higher levels of S. copri and E. coli relatives. The study emphasizes that the effect of dietary components must be viewed within the context of the entire bacterial community, paving the way for more personalized dietary and microbiome strategies.