A new microscopy technique reveals how bacteria feel surfaces

What is it about?

In natural environments, bacteria rarely live as free-swimming cells but are usually attached to surfaces as biofilms in medical devices, mobile phones or human tissue. Their behavior, i.e. how they attach and grow, group together or excrete compounds that glue the biofilm, is influenced by their mechanical interaction with the surface. Understanding bacteria-surface interactions is essential for tackling biofilm formation, developing antibacterial materials, and advancing biosensing technologies. Our work shows a novel approach to visualize and quantify the mechanical stress experienced by bacterial membranes upon contact with surfaces. Using fluorescence lifetime imaging microscopy (FLIM) and a mechanosensitive fluorescent probe known as Flipper-TR, it is possible to measure subtle variations in membrane tension in live bacteria interacting with different materials. This innovative method provides a direct window into the physical forces at play at the bacterial interface. The probe Flipper-TR® is a commercially available fluorescent reporter that specifically targets the membrane of cells. The probe is composed by two moieties that become planarized under compression within the bacterial membrane and twist out of planarity when tension is released, resulting in changes in fluorescence lifetime (the average amount of time a molecule spends in the excited state before returning to ground state, usually in the order on nanoseconds). Flipper-TR has mostly been used in mammalian cells and few reports include bacteria due to experimental difficulties. Our work now shows that this probe is suitable for both Gram positive and negative bacterial model systems. Moreover, it is sensitive enough to discriminate bacterial contact with surfaces with different adhesive and topological properties, even detecting membrane stretching when bacteria are placed on nanostructured, mechano-bactericidal substrates.

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Photo by National Institute of Allergy and Infectious Diseases on Unsplash

Photo by National Institute of Allergy and Infectious Diseases on Unsplash

Why is it important?

The underlying biophysical mechanisms of bacteria-surface interaction remain largely unexplored. How bacteria “feel” and respond to surfaces can have a profound effect on bacterial physiology. These findings open the way to understanding how mechanical cues influence bacterial physiology and offer design principles for creating bio-interactive materials that either discourage or promote bacterial adhesion, with potential applications in healthcare, biotechnology, and materials science

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