Ironing out the details: what causes a biofilm to wrinkle?

Wrinkles are generally thought of as a bad thing — in clothes, in fabrics, and even in science. In biology, wrinkly biofilms can disrupt surgeries, water pipes, and ship hulls, and they are notoriously hard to get rid of in any context.

Krishnan et al. set out to understand why biofilms wrinkle and the mechanism behind this phenomenon.

“Biofilm wrinkles can have a functional role in different species: for instance, maximizing the surface-to-volume ratio to increase respiration or generating channels to enable nutrient diffusion within the biofilm and allow the bacteria to keep growing,” said author Diana Fusco. “Whether wrinkles, or other architectural features in the biofilm, are the results of evolution is an open and intriguing question.”

In general, wrinkling is caused when the mass of the film builds up an internal pressure that can’t be released quickly enough. As a result, wrinkles can be affected by internal factors like genetics and external factors like the environment.

“Interestingly, most of the external factors seem to lead to wrinkle formation only within an optimal range, when the factor is neither too weak, nor too strong,” said Fusco.

Biofilms play an important role in filtration and bioenergy production, so understanding their complex architecture, including wrinkling, is helpful to mitigating their detriments and optimizing their applications.

“While well-studied model species, such as B. subtilis, E. coli, V. cholerae and P. aeruginosa would still be useful for systematic environmental and genetic studies, I think multi-species biofilms are a relatively uncharted territory that holds a lot of research potential to better understand the ecological factors that shape biofilm formation,” said Fusco.

Source: “The what, when, where, and why of wrinkly morphology in biofilms,” by N. Krishnan, J. Knight, C. Tropini, L. Ruiz Pestana, and D. Fusco, Biophysics Reviews (2025). The article can be accessed at https://doi.org/10.1063/5.0223707 .