Various mechanisms have been proposed to explain the role of
calcium and magnesiumin bacterial adhesion and bio film formation, including:
partial neutralization of repulsive electrostatic forces between
bacteria and substrate; formation of divalent cationic
bridges between negatively charged functional groups on bacterial
cell walls and the substrate ; interactions
of calcium with extracellular DNA ; and modulation of extracellular
polysaccharide formation by bacteria .