Bacterial brawls mark life in the gut's microbiome

March 8, 2016 by Bill Hathaway, Yale University
Bacterial brawls mark life in the gut’s microbiome

Bacterially speaking, it gets very crowded in the human gut, with trillions of cells jostling for a position to carry out a host of specialized and often crucial tasks. A new Yale study, published the week of March 7 in the journal of the Proceedings of the National Academy of Sciences suggests these "friendly" bacteria aggressively stake out their territory, injecting lethal toxins into any other cells that dare bump into them.

"These bacteria are friendly to us, but possess an elaborate arsenal to protect their space," said Aaron Wexler of the Department of Microbial Pathogenesis at the Microbial Sciences Institute at West Campus and lead author of the study. "We've come to view this as a way bacteria check up on their neighbors—as if asking 'Are you the same as me?'"

Gut bacteria have co-evolved in mammals to take on many tasks crucial to health. While we provide the bacteria with nutrients and a warm place to live, they harvest indigestible parts of our diet, produce vitamins we can't make, fend off dangerous pathogens, and fine-tune our immune systems. Bacteria also help each other—for instance some have evolved to consume byproducts of other species.

Wexler and senior author Andrew Goodman wanted to explore how these manage to function together packed into such close proximity. To their surprise, they found bacteria were in almost constant warfare with each other.

They found members of the phylum Bacteroidetes—one of the major groups of bacteria in the gut—have developed mechanisms to "hand-deliver" toxins into neighboring cells and to defend against toxins injected by similar cells. Immunity proteins produced within the provide defenses against these toxins and ensure co-existence with similar cells. For reasons not well understood, only a subset of members within a given species possesses these defenses.

"Even in the same species the arsenals can be different," Goodman said. "They are defining who is who at a much finer level than species. It seems to be a way to keep competitors at arm's length."

Understanding how these toxins work may one day have clinical relevance, the authors say, given increased understanding of how the disruption of the microbiome can play a role in cancer, obesity, and autoimmune diseases.

Explore further: Research explains how we live in harmony with friendly gut bacteria

More information: Human symbionts inject and neutralize antibacterial toxins to persist in the gut, Proceedings of the National Academy of Sciences , www.pnas.org/cgi/doi/10.1073/pnas.1525637113

Related Stories

Skin bacteria help cancer cells grow

January 6, 2016

Our skin is covered in millions of bacteria and most of them help keep us healthy. However, for patients with lymphoma, it may be a rather different story, as new research from the University of Copenhagen shows that toxins ...

Antibiotic resistance is a gut reaction

December 16, 2014

Scientists from the Institute of Food Research and the University of East Anglia have discovered how certain gut bacteria can protect themselves and others in the gut from antibiotics.

Recommended for you

Computing the origin of life

December 14, 2018

As a principal investigator in the NASA Ames Exobiology Branch, Andrew Pohorille is searching for the origin of life on Earth, yet you won't find him out in the field collecting samples or in a laboratory conducting experiments ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.