Dynamic remodeling of microbial biofilms by functionally distinct exopolysaccharides

Area of Science:

• Microbiology and Microbial Ecology
• Biomaterials Science
• Biophysics

Background:

• Biofilms are microbial communities encased in an extracellular matrix, crucial for their structure and function.
• The biofilm matrix, composed of biopolymers, significantly impacts cell physiology, communication, and interspecies interactions.
• Quantitative understanding of biofilm matrix microstructure and microrheology remains limited, hindering effective biofilm control strategies.

Purpose of the Study:

• To investigate the distinct rheological contributions of exopolysaccharides Pel and Psl in Pseudomonas aeruginosa biofilms.
• To elucidate the roles of Pel and Psl in biofilm structure, development, and interspecies interactions.
• To explore how bacteria modulate matrix physical properties to influence biofilm behavior.

Main Methods:

• Particle-tracking microrheology was employed to spatially and temporally study matrix properties.
• Genetic approaches were utilized to analyze the roles of Pel and Psl exopolysaccharides.
• A mixed-species biofilm model involving P. aeruginosa and Staphylococcus aureus was used to assess interspecies interactions.

Main Results:

• Psl enhances biofilm matrix elasticity and cross-linking, strengthening the scaffold and promoting microcolony formation.
• Pel reduces matrix cross-linking, while its absence leads to a more viscous matrix that facilitates biofilm spreading.
• Pel is essential for close association between P. aeruginosa and S. aureus in mixed biofilms; Psl aids P. aeruginosa in forming single-species biofilms on S. aureus.

Conclusions:

• Pel and Psl possess distinct physical properties and functional roles in biofilm formation and architecture.
• Bacteria can actively remodel their biofilm matrix by controlling exopolysaccharide production, impacting biofilm development and surface colonization.
• Understanding the specific roles of matrix components like Pel and Psl is vital for developing targeted strategies against challenging biofilms.