Linking Matrix Composition with Spatially Resolved Mechanical Properties in Polymicrobial Biofilms

This award will support research to understand the mechanistic underpinnings of biofilm mechanical and physical properties. Biofilms are soft multi-component biological materials. They are made of microbial communities attached to surfaces and encased in polymeric substances.

It is thought that these polymeric substances provide mechanical stability. Detrimental biofilms cause billions of dollars per year of damage via biofouling or corrosion of ship hulls, heat exchangers, water treatment and distribution infrastructure, membranes, and in the food, oil, and beverage industries. In addition, they account for 65% of infections that originate in hospitals, affecting 17 million people and causing at least 550,000 deaths annually in the US.

Conversely, beneficial biofilms can clean water and remediate groundwater and soil. Despite the crucial relevance of biofilms to diverse industrial, medical, and environmental applications, little is known about how local biofilm mechanical properties are mediated by encasement composition, community diversity, and biofilm physical structure. This award will support fundamental research to understand the relationship between microscale biofilm mechanical properties, encasement and community composition, and physical structure.

This work will study biofilms of increasing complexity, including complex environmentally-relevant mixed-culture biofilms. The results generated from executing this award will directly inform new strategies to manage biofilms in critical applications (e.g., remove when they are undesirable, and retain when they are beneficial), leading to significant cost savings.

The project provides additional benefits, including diversifying the nation’s STEM workforce through multidisciplinary training for underrepresented students at grade school, undergraduate, and graduate levels.

This grant will advance our understanding of critical yet poorly understood interrelationships between molecular composition, physical structure, and mechanical properties in polymicrobial biofilms exposed to disparate environmental cues. The majority of the work to date on biofilm mechanical properties has employed macrorheological tools that neglect the inherent local heterogeneity in biofilms and has focused primarily on pure culture biofilms (e.g., P. aeruginosa alone) that are not representative of, and likely differ significantly in extracellular polymeric substances (EPS) composition and mechanical properties from, polymicrobial biofilms that are found in medical, environmental and industrial settings.

Specifically, the research team will, 1) study local structure- composition-viscoelastic property relationships in biofilms; 2) study biofilmsubstratum adhesion and cohesion properties; and 3) develop homogenization-based constitutive models to predict the multi-scale mechanical properties of biofilms. Project results will elucidate, for the first time, how microscale variations in EPS constituents (e.g., polysaccharides, proteins, eDNA) mediate local heterogeneity in shear moduli and viscosity, adhesion strength, and cohesive fracture energy in dual and mixed-culture biofilms, and how environmental cues and microbial populations present modify this relationship.

This improved understanding of spatially resolved structure/ composition- mechanical property relationships will provide the basis for rational management and control of biofilms.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.