Abstract
Adaptive responses greatly improve the competitive capacities of bacteria in diverse environments. Here, we investigate whether bacteria can adapt to a microenvironment with distinctive softness by examining the type-IV pili (TFP)-mediated motility of Pseudomonas aeruginosa cells on brush-like surfaces that are grafted with a layer of thermally sensitive polymer chains, where the softness of the brush-layer is tunable by applying a small temperature change (from 30 to 37 °C). We report that P. aeruginosa cells slingshot more on soft surfaces at a shear-thinning condition, which greatly facilitates their surface crawling by means of reducing energy dissipation. This adaptive response suggests that P. aeruginosa cells may be able to sense the local viscoelasticity and then deploy TFP to adapt to their physical surroundings.
Highlights
Adaptive responses greatly improve the competitive capacities of bacteria in diverse environments
After carefully excluding other possible factors, we demonstrate that bacteria deploy their TFP to slingshot more on soft surfaces at a shear-thinning condition
Our results show normal bacterial growth and subsequent nascent biofilm formation on PNIPAAM brush surfaces, as shown in Supplementary Fig. 4, demonstrating that these brush surfaces are non-toxic for P. aeruginosa
Summary
Adaptive responses greatly improve the competitive capacities of bacteria in diverse environments. We report that P. aeruginosa cells slingshot more on soft surfaces at a shear-thinning condition, which greatly facilitates their surface crawling by means of reducing energy dissipation This adaptive response suggests that P. aeruginosa cells may be able to sense the local viscoelasticity and deploy TFP to adapt to their physical surroundings. Aside from chemical cues, different abiotic/biotic surfaces often possess distinctive physical properties, such as viscoelasticity; for example, there is a shear modulus difference of at least six magnitudes between tissues and alloyed bone nail surfaces, yet bacterial biofilms can form on both[18] It is less certain whether, especially at the singlecell scale, bacteria can adapt TFP-mediated motility or other surface motilities in response to their physical surroundings; only a few investigations suggest that bacteria do so[4,19,20]. PNIPAAM brush surfaces can be tuned from soft to hard by only a small temperature change from 30 to 37 °C
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