Individualized microbiotas determine the impact of dietary fiber on colitis sensitivity. The study shows that the response of the intestinal microbiota to dietary fiber varies significantly between individuals, influencing their susceptibility to colitis. Using an in vitro microbiota modeling system, the researchers found that some microbiotas are highly responsive to soluble fibers like inulin and psyllium, altering their composition, pro-inflammatory potential, and metabolomic profile. In contrast, other microbiotas show minimal changes. When mice were transplanted with microbiotas sensitive to fiber, their colitis severity was significantly affected by soluble fiber consumption, while those with resistant microbiotas showed colitis regardless of fiber intake. The study highlights that the impact of dietary fiber on colitis is highly dependent on individual microbiota composition, suggesting that personalized fiber-based interventions could be beneficial for both IBD patients and healthy individuals. The findings indicate that the microbiota's ability to ferment dietary fibers and its functional characteristics, such as the presence of Faecalibacterium prausnitzii, play a key role in determining fiber sensitivity. The study also shows that fiber-sensitive microbiotas can modulate colitis severity when transplanted into germ-free mice, while fiber-resistant microbiotas do not. These results support the idea that the microbiota's response to dietary fiber is highly individualized and that understanding this variability could lead to more effective, personalized dietary interventions.Individualized microbiotas determine the impact of dietary fiber on colitis sensitivity. The study shows that the response of the intestinal microbiota to dietary fiber varies significantly between individuals, influencing their susceptibility to colitis. Using an in vitro microbiota modeling system, the researchers found that some microbiotas are highly responsive to soluble fibers like inulin and psyllium, altering their composition, pro-inflammatory potential, and metabolomic profile. In contrast, other microbiotas show minimal changes. When mice were transplanted with microbiotas sensitive to fiber, their colitis severity was significantly affected by soluble fiber consumption, while those with resistant microbiotas showed colitis regardless of fiber intake. The study highlights that the impact of dietary fiber on colitis is highly dependent on individual microbiota composition, suggesting that personalized fiber-based interventions could be beneficial for both IBD patients and healthy individuals. The findings indicate that the microbiota's ability to ferment dietary fibers and its functional characteristics, such as the presence of Faecalibacterium prausnitzii, play a key role in determining fiber sensitivity. The study also shows that fiber-sensitive microbiotas can modulate colitis severity when transplanted into germ-free mice, while fiber-resistant microbiotas do not. These results support the idea that the microbiota's response to dietary fiber is highly individualized and that understanding this variability could lead to more effective, personalized dietary interventions.