University of California Los Angeles: How bacteria sense surfaces to form films

The bacterium known as Pseudomonas aeruginosa is an unwelcome visitor in the human body. Serious infections can result when a bunch of these bugs settle together on a surface to form a biofilm — a community of microbes like the slime on spoiled food, but in this case residing inside a person. The grouped-up bacteria attack the lungs of patients with cystic fibrosis and conditions that require the use of ventilators, such as severe COVID-19. Worse still, the World Health Organization lists Pseudomonas among the antibiotic-resistant bacteria presenting the biggest threat to human health.

Now, however, new findings from researchers led by the California NanoSystems Institute at UCLA (CNSI ) reveal just how Pseudomonas go from exploring a surface to committing to it and building a community — a key finding that can help pave the way to understanding how to tackle these types of infections.

The new study revealed how Pseudomonas detects and binds to specific sugars left behind by others from its species that arrived earlier. The cell senses these sugar trails using proteins on its body, and then identifies the sugars using hairlike appendages called pili. These pili are normally used to crawl along a surface, but in this case double as mechanical sensors that test the strength of the sugar bonds. All of this information is translated into chemical signals inside the cell that guide the operation of other bacterial machinery, such as the controlled secretion of more sugars to make biofilms.

Reported in the journal Nature Microbiology, the results may inform applications in human health and industry. For Pseudomonas, the findings could lead to better approaches for undermining the dangerous bugs' ability to resist drug treatments.