The team from the University of Freiburg and the Excellence Cluster Centre for Integrative Biological Signalling Studies used live cell imaging microscopy and found the bacteria makes close contact with cells and indents the membrane until the cell is completely engulfed by P.a. (Cell Reports, October 18, 2022).

Pseudomonas dent cell membranes by binding the virulence factor LecA to sugar molecules on the membrane's surface. The researchers decided to focus on septins as they can also encapsulate bacteria that have already penetrated the cell and induce the bacteria's liquidation.

Using human lung cells infected with P.a., the researchers observed septins gathered at the site within a few seconds or minutes and if the bacteria failed to penetrate, the accumulation then dissolved quickly. The same effect occurred when small polymer beads coated with LecA were given to the cells and induced septin accumulation.

The scientists also attached the minimal bacterial model to the cantilever of an atomic force microscope, which measures the tiniest of indentations and resistances as force. Doing so, they discovered the cell membrane was more rigid locally when the polymer beads were coated with LecA and again septin accumulated.

The results indicate septins play a significant role in warding off infections and now the researchers intend to continue studying lectins and septins, which could aid in finding points of attack for drugs designed to prevent infection by antibiotic-resistant bacteria, they said.