CRISPR Was the ‘Commander in Chief’ of Bacterial Defense, With a Hidden Function Discovered

A new study has found that the CRISPR-Cas gene-editing system not only protects bacteria from viruses but also acts as a “commander in chief” that regulates the expression of other embedded immune genes.

On the 27th (local time), a joint research team from the University of Michigan Medical School and the Institute of Microbiology at the Chinese Academy of Sciences said it had published a paper containing these findings in the international journal Nature. The team discovered this feature in the Type I CRISPR system of Neisseria bacteria.

According to the research team, the Type I CRISPR system normally suppresses the expression of other defense genes present inside bacteria. This prevents bacterial growth from being impaired by the unnecessary activation of defense systems.

However, the situation changes when a phage, a virus that infects bacteria, neutralizes CRISPR’s first line of defense. As the suppression is lifted, genes for embedded secondary defense systems are expressed at high levels. The research team explained that this is a hierarchical defense system in which “backup weapons” are activated to eliminate phages.

Yan Zhang, a professor at the University of Michigan Medical School, said, “CRISPR is the first line of defense, but when it is compromised, the suppression is lifted and the embedded defense systems are produced in large quantities.”

The discovery is expected to contribute to the development of phage therapies targeting antibiotic-resistant bacteria. The research team explained that understanding bacteria’s hidden defense systems could make it possible to design phages capable of overcoming them. It could also be applied to developing strains with greater resistance to phages in industries that use bacteria, such as yogurt and biofuels.