Electroactive biofilms alter the EPS structure and metabolic pathways to sense potential and tetracycline

The extracellular polymeric substances (EPS) secretion decides the efficiency of microbial electron transfer and the resistance to toxic challenges. Electrode potential is a critical factor affecting both the rate and direction of electron transfer. However, the mechanism through which potential regulates EPS structure and toxic substance removal remains unclear. This research suggested that more positive potential stimulated increased extracellular protein and polysaccharides (PS) secretion. Nonetheless, excessive PS secretion restricted the current output, with the limiting current at -0.1 V being 1.39 times that of 0.3 V. A positive potential resulted in a more compact protein structure, but tetracycline (TC) addition has disrupted the polypeptide structure of EAB, while the α-helix and α-helix/β-sheet at -0.1 V was superior to other potentials. Under -0.1 V, the EABs maintained more abundant Geobacter (86 %) and cellular activity when sensing to the toxic of TC. The degradation rates observed at this potential was 1.5 times that of high potential, largely due to the upregulation of amino acid metabolic pathways. This study demonstrates the potential of using electrode potential to regulate the balance of EPS for electron transfer and self-protection, providing theoretical support for manipulating extracellular polymer secretion through electrode potential to enhance bioremediation of pollutants.