Bacterial Swarmers Enriched During Intestinal Stress Help Heal Damage

Researchers aimed to determine the occurrence and consequence of bacterial swarming in humans and mice in the context of intestinal stress.

A new paradigm in which intestinal stress allows for the emergence of swarming bacteria has been demonstrated and these bacteria have been shown to heal intestinal inflammation, according to a study published in Gastroenterology.

Bacterial swarming is a collective and rapid movement across a surface, but the functional importance and consequence of bacterial motility in a microbial consortium is unknown. Researchers aimed to determine the occurrence and consequence of bacterial swarming in humans and in the animal kingdom, in the context of a stressed and non-stressed intestinal environments.

In addition, the researchers sought to uncover potential mechanisms by which swarming bacteria interact with the host. Investigators developed techniques to isolate the dominant swarmers in chemically induced colitis in mice as well as humans with inflammatory bowel disease (IBD) and found that bacterial swarmers are highly predictive of intestinal stress in both species.

The researchers isolated a novel Enterobacter swarming strain, SM3, from mouse feces. SM3 and other known commensal swarmers, in contrast to their mutant strains, abrogated intestinal inflammation in mice. Treatment of colitic mice with SM3, but not its mutants, enriched beneficial fecal anaerobes belonging to the family of Bacteroidales S24-7. The researchers observed SM3 swarming associated pathways in the in vivo fecal meta-transcriptomes. In vitro growth of S24-7 was enriched in the presence of SM3 and its mutants. However, because SM3, but not its mutants, induced S24-7 in vivo, the researchers concluded that swarming plays an essential role in disseminating SM3 in vivo.

“In summary, our work demonstrates the unique and unprecedented role that bacterial swarmers play in intestinal homeostasis,” stated the authors. They added, “We found the potential for a new personalized ‘probiotic’ approach stemming from the ability to isolate and bank swarming microbes during colitic episodes.”


De A, Chen W, Li H, et al. Bacterial swarmers enriched during intestinal stress ameliorate damage. Gastroenterol. Published online March 15, 2021. doi: 10.1053/j.gastro.2021.03.017