Stress often causes bacteria to form biofilms. The stress can be in the form of a physical barrier, ultraviolet light, or a toxic substance such as antibiotics. These biofilms take from hours to days to form and can be of various shapes, sizes, colors, and textures depending on the species of bacteria involved.

Being in the state of a biofilm protects them from hazardous substances in their environment — biofilms have a unique outer wall, with different physical and chemical properties than their individual cells. They can coordinate metabolically, slow their growth, and even form an impenetrable barrier of wrinkles and folds.

This is one way they achieve high antibiotic resistance. Researchers from the United Kingdom recently studied the bacteria B. Sultilis transition from a free-moving swarm to a biofilm as a defense mechanism and published what they did to combat its antibiotic resistive properties in eLife.

To determine if their test strain behaves as others do, they recreated first performed stress tests on them. They tested the bacteria’s response to a physical barrier, ultraviolet light, and an antibiotic. The addition of a physical barrier led to a single-to-multi-layer transition of the bacteria, followed by an increase in cell density and the formation of multilayer islands near the barrier. Later, wrinkles developed on the islands near the barrier in the area the islands had started to appear initially.

When they applied ultraviolet light to the swarm, they again observed a drop in cell speed and an increase in density. And after the scientists added a large dose of the antibiotic kanamycin the bacterial cells formed a biofilm. The researchers then devised a strategy to tackle this bacteria biofilm.

They added kanamycin to the environment of a new batch of swarming bacterial cells and watched as a biofilm began to take shape. They then re-administered the antibiotic in a much larger dose than the first one, just before the completion of the biofilm’s formation. The breakdown of the partially formed biofilm and the death of the bacterial cells occurred as a result.

This shows that antibiotic-resistant bacteria lose their resistance to antibiotics when they undergo a phase transition, right before transitioning to a biofilm, where they would become much more resilient. So with proper timing of the administering of antibiotics, bacteria can be attacked in their most vulnerable state and eliminated. Researchersbelieve similar swarm-to-biofilm transitions occur in other bacterial species too.

Their research could pave the way to finding more effective ways of managing clinically relevant bacteria. Such as Salmonella enterica which spreads to the bloodstream and is transmitted by contaminated food. Or the multidrug-resistant Pseudomonas aeruginosa which causes infections in the blood, lungs (pneumonia), and other parts of the body after surgery and is spread in hospitals.