April 29, 2025 – Scientists at the Hebrew University of Jerusalem have uncovered a surprising way in which harmful bacteria prepare to attack their hosts. The discovery, led by Ph.D. students Lior Aroeti and Netanel Elbaz under the guidance of Prof. Ilan Rosenshine from Hebrew University’s Faculty of Medicine, could one day help researchers find new ways to fight infectious diseases.

At the heart of this study is a protein called CsrA, which acts like a switchboard operator inside bacterial cells. It helps bacteria decide which of their genes to turn on or off, especially the genes that make them dangerous to humans.

Researchers have long known that CsrA plays a central role in bacterial virulence—the ability of bacteria to cause disease. But the new study shows that CsrA doesn’t work alone. Instead, it gathers in a special, droplet-like structure inside the cell. This structure has no membrane, making it a “membraneless compartment,” which scientists now believe is crucial in regulating how bacteria behave.

“This compartment acts like a temporary control center,” explained Prof. Rosenshine. “It helps bacteria shift gears—either gearing up to infect or slowing down to conserve energy.”

Using glowing proteins to track CsrA inside bacteria, the team discovered that these compartments form naturally under certain conditions, especially those that mimic the human gut. They also found that these structures include other key molecules that help bacteria manage their genetic activity.

One of the most exciting findings is that these compartments might be common across many different kinds of bacteria, not just one species. This could mean that similar mechanisms are being used by a wide range of pathogens to control how and when they become dangerous.
Prof. Rosenshine’s research provides a new window into how bacterial cells are organized and how they adapt to their environment. Understanding this could pave the way for future treatments that stop bacteria from becoming harmful in the first place.

The research paper titled “Formation of a membraneless compartment regulates bacterial virulence” is now available in Nature Communications and can be accessed here.

Researchers:
Lior Aroeti1, Netanel Elbaz1, Raya Faigenbaum-Romm1,2, Oren Yakovian1,2, Yael Altuvia1, Liron Argaman1, Naama Katsowich1, Michal Bejerano-Sagie1, Miriam Ravins1, Hanah Margalit1, Sigal Ben-Yehuda1 & Ilan Rosenshine1

Institutions:
1)    Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem
2)    Racah Institute of Physics, The Hebrew University of Jerusalem