Cathodic polarization enables SEM illustration of manganese biomineralization in natural biofilms

Manganese biomineralization occurred readily on metal surfaces in a natural freshwater environment. SEM demonstration of actual bacterial participation was challenging due to the rapidity of biofilm growth and typical microbe-mineral agglomeration. By optimizing cathodic polarization, we slowed down the process so effectually as to document biomineralization by rod-shaped rather than by filamentous bacteria which occurred more frequently at open circuit.