Pili-based 'Toe-dipping' Phenomena Preceding Solid Surface-Associated Microbial Biofilm Formation in Pseudomonas aeruginosa

The review focuses on the molecular mechanisms surrounding bacterial pili triggered biofilm formation in a prime nosocomial infection pathogen i.e. Pseudomonas aeruginosa. Bacterial biofilm formation is a major biomedical challenge driving antibiotic resistance and persistent hospital-and biomaterialassociated infections, and existing antibiofilm strategies often show limited efficacy and poor cytocompatibility, highlighting the urgent need for improved antibiofilm strategies. We critically reviewed current antibiofilm strategies targeting biofilm-associated proteins in P. aeruginosa and found that none of the aforementioned strategies are entirely efficacious, highlighting the need to reexamine our understanding of the signaling pathways governing biofilm formation. therefore subsequently we reexamined the key pathways that were involved in biofilm formation and identifies surface sensing as a central regulatory mechanism influencing all extracellular polymeric substance (EPS) production-related pathways. Following this insight, we further examine the surface-sensing mechanism mediated by the Type IV pilus (T4P) tip protein PilY1. Upon surface contact, PilY1 triggers intracellular signalling that rapidly elevates cyclic-di-GMP levels, a key second messenger driving EPS synthesis and biofilm maturation. Further, the PilY1-mediated process of surface mechano-sensing plays a crucial role in coordinating biofilm formation through various interconnected regulatory pathways. However, the existing literature suggests that PilY1 has not been directly targeted therapeutically, revealing a critical gap in current pili-based antibiofilm intervention strategies. Addressing this unmet gap, our review, based on extensive literature analysis and mechanistic insights, we conclude that disrupting pilus-based surface sensing represents a highly effective strategy to inhibit EPS production and, consequently, biofilm formation in P. aeruginosa and other Gram-negative bacteria. In addition, this review provides insight into pilus-mediated surface-sensing strategies that could be key foundations for anti-biofilm coatings for biomedical and related anti-fouling applications.