Sped-up evolution may help bacteria take hold in gut microbiome, UCLA-led research team finds

Everywhere you go, you carry a population of microbes in your gastrointestinal tract that outnumber the human cells making up your body.

This microbiome has important connections to health in your gut, brain and immune system. Some resident bugs produce vitamins, antioxidants, nutrients and other helpful compounds. Even those whose direct effects seem neutral take up space that makes it harder for harmful microbes to move in.

There is still much to be understood about the gut microbiome, but its connections to health suggest the potential for curating this community to address disease. New discoveries from a research team at the California NanoSystems Institute at UCLA, or CNSI, offer a promising step in that direction.

The scientists investigated a known mechanism that changes genes in microbes, driven by what are called diversity-generating retroelements. DGRs carry collections of genes that function together to create random mutations in specific hotspots in bacterial genomes. Effectively, they accelerate evolution in their hosts, enabling microbes to change and adapt.

DGRs are more common in the gut microbiome than any other environment on Earth where they've been measured. However, their role in the gut has not been investigated until now.

In a study published in the journal Science, the team explored bacteria commonly seen in the healthy digestive tract. They found that about one-quarter of those microbes' DGRs target genes vital for latching on to grow colonies in new surroundings. The researchers also demonstrated that DGRs travel well: They can transfer from one strain of bacterium to others nearby, and infants inherit DGRs from their mothers that seem to aid in starting up the gut microbiome.

"One of the real mysteries in the microbiome is exactly how bacteria colonize us," said senior author Jeff F. Miller, director of CNSI, holder of the Fred Kavli Chair in NanoSystems Science and a professor of microbiology, immunology and molecular genetics at UCLA. "It's a highly dynamic system intimately connected with human physiology, and this knowledge about DGRs could one day be applied for engineering beneficial microbiomes that promote good health."

Read more about the team's findings on the CNSI website.