The effects of air/water interface properties on the formation of biofilm by P. aeruginosa

Microbial biofilms are viscoelastic materials formed by bacteria, which occur on solid surfaces, at liquid interfaces, or in free solution. Although solid surface biofilms have been widely studied, pellicles, biofilms at liquid interfaces, which can be found in crude oil processing, aquatic ecosystems, and wastewater treatment, have had significantly less focus. Depending on the application, enhancing, or preventing their growth can be important. Studies have shown that biofilms are viscoelastic materials that they respond elasticity to mechanical deformation on short time scales and as a viscous fluid on long time scales. Characterizing the mechanical properties of the biofilms, specifically by looking to their viscoelasticity as soft materials can gain more insight into the mechanics of biofilms. In this work, interfacial shear rheology and SEM imaging are used to characterize how flagella, type IV pili, bio-surfactants, and EPS polysaccharides affect the formation of pellicles formed by P. aeruginosa at an air/water interface. Also, to interpret biofilm viscoelasticity, 20 identically grown P. aeruginosa pellicles are studied to understand the statistical variance. Meanwhile, the effects of nonionic surfactants on the formation of P. aeruginosa have been investigated. The results can lead to a better evaluation of biofilm formation in future studies and a stronger ability to compare between studies of P. aeruginosa across the literatures.

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