Bacterial immune system discovery may transform understanding of human viral defence
Israeli researchers unveiled a novel bacterial immune system that may transform science’s understanding of human immunity how to combat viral infections.
The Weizmann Institute of Science in the Israeli city of Rehovot on Sept. 9, 2023. Photo by Yossi Zeliger/TPS
A study by the Weizmann Institute of Science recently published in the peer-reviewed Nature journal centered on phages, viruses that specifically target bacteria.
The microscopic phages consist of a head containing genetic material and a tail used to locate and inject this material into a host bacterial cell. Once inside, the phage commandeers the bacterium’s cellular machinery to replicate itself, ultimately causing the bacterial cell to burst and release new phages to infect other bacteria.
However, the Weizmann study discovered a bacterial defense mechanism that thwarts phages by attaching a small protein molecule to their tails, rendering them incapable of further infection. Significantly, this system shares structural similarities with a human immune mechanism, hinting at evolutionary connections between bacterial and human immunity.
The first known antiphage defenses in bacteria were discovered in the 1960s. Until recently, only a few such mechanisms were recognized, with CRISPR-Cas9 being the most famous, revolutionizing gene editing. The last few years, however, have seen an explosion of discoveries in this field, identifying over 150 new bacterial immune systems, each with unique methods of action.
Many of these discoveries were made using a technique developed by Professor Rotem Sorek of Weizmann’s Molecular Genetics Department. His approach leveraged the tendency of bacterial immune system genes to cluster together in regions of the genome known as “defense islands.” By examining genes of unknown function located near these islands, researchers can identify new immune systems.
“In many of our studies, we have recognized components of bacterial immune systems that were familiar to us from extensively studied human immune mechanisms,” Sorek explained. “This suggests that the evolutionary source of a large part of our innate immune system comes from bacteria. Our new study provides further support for this idea.”
In the 1970s, scientists discovered ubiquitin, a small protein that can alter the structure, function, and lifespan of other proteins by attaching to them. This system of protein modification, for which professors Aaron Ciechanover, Avram Hershko, and Irwin Rose received the 2004 Nobel Prize in Chemistry, has since been found to involve many similar systems. These systems use enzymes to attach various small proteins to target proteins, influencing their fate.
