Scientists at the University of California, San Francisco (UCSF) have discovered how a bacterial pathogen breaks down the natural barriers that protect human cells from infection. The findings, published in the journal *Nature*, could lead to new treatments for bacterial infections, which are a major cause of death worldwide.

The bacterium in question is *Pseudomonas aeruginosa*, a common pathogen that can cause a variety of infections, including pneumonia, bloodstream infections, and urinary tract infections. *P. aeruginosa* is particularly dangerous for people with weakened immune systems, such as those with cystic fibrosis or cancer.

The researchers found that *P. aeruginosa* produces a protein called ExoU that helps the bacterium break down the tight junctions between human cells. Tight junctions are specialized proteins that hold cells together and create a barrier that prevents harmful substances from entering the body.

By breaking down the tight junctions, ExoU allows *P. aeruginosa* to enter and infect cells. This can lead to a variety of symptoms, depending on the location of the infection.

"This is a significant discovery that could have a major impact on the treatment of bacterial infections," said study leader Melanie A. Newport, PhD, a professor of medicine at UCSF. "By understanding how *P. aeruginosa* breaks down the natural barriers that protect human cells, we can develop new drugs that prevent or inhibit this process."

The researchers are currently working on developing new drugs that target ExoU. These drugs could potentially be used to treat a variety of *P. aeruginosa* infections, including those that are resistant to antibiotics.

"We are excited about the potential of this research to lead to new treatments for bacterial infections," said Newport. "We hope that our findings will help to improve the lives of people with these devastating diseases."