Biofilm and swarming emergent behaviours controlled through the aid of biophysical understanding and tools

Abstract

Bacteria can organise themselves into communities in the forms of biofilms and swarms. Through chemical and physical interactions between cells, these communities exhibit emergent properties that individual cells alone do not have. While bacterial communities have been mainly studied in the context of biochemistry and molecular biology, recent years have seen rapid advancements in the biophysical understanding of emergent phenomena through physical interactions in biofilms and swarms. Moreover, new technologies to control bacterial emergent behaviours by physical means are emerging in synthetic biology. Such technologies are particularly promising for developing engineered living materials (ELM) and devices and controlling contamination and biofouling. In this minireview, we overview recent studies unveiling physical and mechanical cues that trigger and affect swarming and biofilm development. In particular, we focus on cell shape, motion and density as the key parameters for mechanical cell-cell interactions within a community. We then showcase recent studies that use physical stimuli for patterning bacterial communities, altering collective behaviours and preventing biofilm formation. Finally, we discuss the future potential extension of biophysical and bioengineering research on microbial communities through computational modelling and deeper investigation of mechano-electrophysiological coupling.

Keywords: active matter; biofilms; living materials; pattern engineering; physics of microbes; swarming.

Figure 1.

Different Physical properties can regulate microbial swarming (left) and biofilm (right) collective behaviour and development. Soft substrates that are rich in nutrients promote swarming bacteria formation (left) whereas hard substrates and, in general, nutrient depletion promotes biofilm formation (right). Swarming motility is enhanced by the cell density and short aspect ratios. In biofilms, cells of large aspect ratios are found at the bottom and rounded cells in upper layers and the differences in cell density provide the biofilms’ typical wrinkle-like structure. Light can drive the expanding direction swarms in phototactic bacteria and tune their cell speed leading to patterns and inhomogeneities in cell density. In biofilms, light can be used to control single cell attachment in synthetic engineered bacteria or to trigger biofilm dispersion through cell hyperpolarization. Biofilm inhibition is also possible by surface undulation at certain amplitude and frequency and its shape and degree of attachment can be altered by external shear flows. Both biofilms and swarms can be organised into arbitrary patterns through 3D printing and MeniFluidics. See also accompanied table.