Colonization of bioelectrochemical system biofilms by low-adhesive denitrifiers: Promotion by electroactive bacteria

Bioelectrochemical systems (BESs) represent a promising advanced technology for enhanced denitrification of wastewater, with electroactive biofilm (EAB) serving as the functional core. Reducing the loss of low-adhesive denitrifying bacteria in EAB is critical to the functionality and stability of efficient denitrification. This study constructed a co-culture BES with electroactive Geobacter sulfurreducens and low-adhesive denitrifier Thauera aminoaromatica to investigate biofilm colonization patterns and intrinsic mechanisms. The system demonstrated a significant facilitation of denitrifier colonization, with the cell density of T. aminoaromatica in biofilms increasing 186-fold compared with pure culture. XDLVO theoretical analysis revealed that electroactive bacteria colonized the carrier surface first, remodeled electrode interface thermodynamic properties, and eliminated the thermodynamic energy barrier for planktonic bacteria to approach the surface. T. aminoaromatica senses co-culture microenvironmental signals to actively enhance its adhesion and colonization ability, upregulating c-di-GMP accumulation to reduce motility via two-component system-mediated adaptive chemotaxis regulation. The thermodynamically optimized electrode interface in BESs and the enhanced adhesion and colonization ability of denitrifier synergistically reduce the loss of functional microorganisms and accelerate the establishment of their dominant niches. This study provides a regulatory pathway and theoretical basis for biofilm formation and functional microorganism enrichment in denitrifying BESs.