Physicochemical, Structural, and Proteomic Insights into Drinking Water-Isolated Acinetobacter calcoaceticus Aggregation and Biofilm Dynamics

Acinetobacter calcoaceticus, a ubiquitous Gram-negative bacterium, exhibits remarkable adaptability across diverse environments, including drinking water distribution systems (DWDS), where its biofilm-forming and coaggregation capabilities pose significant public health challenges. This study integrates physicochemical, structural, and proteomic analyses to elucidate the mechanisms underlying A. calcoaceticus aggregation and biofilm dynamics. Surface characterization through contact angle measurements, zeta potential, and co-adhesion energy assessments revealed a predominantly hydrophilic surface with strong electron donor properties and a highly negative charge, promoting intercellular adhesion. Transmission electron microscopy unveiled dense cellular aggregates with extracellular filamentous structures, indicative of enhanced cell-to-cell interactions and potential extracellular polymeric substance involvement. Proteomic profiling identified 2593 differentially expressed proteins between aggregation stages, highlighting metabolic shifts, stress response activation, and upregulation of biofilm-associated proteins, including chaperones and quorum-sensing regulators. Our multidisciplinary approach emphasizes the importance of surface characterization in understanding bacterial community and underscores the critical role of physicochemical properties and proteomic flexibility in A. calcoaceticus biofilm and aggregation ability.