Scientists at the University of California, San Francisco (UCSF) have successfully edited the genome of bacteria found in the gut microbiome of live mice for the first time.

The authors of the new work used CRISPR technology to change the ratio between different types of bacteria as needed to treat a variety of diseases.

The human intestine contains a huge community of microorganisms. Our health depends on this microbiome, as does the digestive system. Recent studies have shown that the gut microbiome can influence the development of autoimmune diseases – diabetes, cancer, cardiovascular disease, Parkinson’s, Alzheimer’s, and even depression.

The balance of this fragile ecosystem can be upset by inappropriate diet, antibiotics, and many other factors. Probiotics as well as fecal microbiota transplantation can help, but this does not always lead to the desired result.

The authors of the new work decided to study how gene editing of gut bacteria can help restore balance in the microbiome. They wanted to target specific strains of bacteria without affecting others that might be beneficial.

Researchers have tested their method on E. coli – it has strains that are beneficial, as well as those that cause food poisoning and other diseases. In tests in mice, the team developed a bacteriophage called M13, a virus that specifically tracks down a specific strain of E. coli. When the virus takes hold in the body, it transfers CRISPR-Cas9 to the target bacteria and removes chromosomes.

The team orally administered M13 to mice and tracked microbiome changes by analyzing animal feces. Before starting treatment, the target strain dominated their intestines, but after two weeks it was only 1% of the total weight.

According to the authors, the new method can be used to alter the composition of the microbiome. This will help correct the imbalances responsible for health problems.