Exploring bacterial coaggregation in aquatic systems using advanced physicochemical and imaging techniques

Coaggregation is a specific interaction mechanism where genetically distinct bacteria recognize and adhere to each other via complementary protein adhesins and polysaccharide receptors. Despite its critical role in biofilm formation and extensive studies in oral environments, coaggregation remains poorly understood in aquatic systems. Understanding coaggregation is crucial due to its significant implications, including its role in multispecies biofilm formation, water quality effects, impacts on engineered systems' performance, and potential biotechnological applications. This study offers an in-depth characterization of the cell surface properties of Delftia acidovorans isolated from drinking water (DW). Two strains showing different coaggregation abilities were selected (005P—coaggregating and 009P—non-coaggregating). The coaggregating 005P strain demonstrated higher surface hydrophobicity and more negative surface charge compared to the non-coaggregating 009P strain. Additionally, 005P showed higher cell surface and co-adhesion energies. Chemical analysis using Fourier-transform infrared spectroscopy revealed subtle differences in the bacterial surfaces, particularly in spectral regions associated with carbohydrates and proteins (860-930 cm-1 and 1212-1240 cm-1). Cryo-electron tomography highlighted distinct differences in pili structures between the strains. The pili in 005P were identified as pili-like adhesins. This research represents the first comprehensive characterization of a coaggregating strain from DW, employing a combination of advanced analytical techniques to provide new insights into the mechanisms driving bacterial coaggregation in aquatic systems.