Bacteria have been studied in bioflotation and bioflocculation processes for impurity removal. Electrostatic forces are important for adsorption of bacteria onto mineral surfaces. In the present study, three strains of bacteria: Bacillus subtilis, Paenibacillus polymyxa and Mycobacterium phlei, are used to emphasize the importance of bacteria-coal electrostatic interaction on coal cleaning. They differ in their point of zero-charge (PZC). Flotation experiments were conducted using each bacterium individually to reduce coal impurities. Although promising results were observed for all studied bacteria, B. subtilis was the best. By correlating the PZC of coal particles as well as the bacteria, it was found that the superiority of B. subtilis is related to wider PZC difference between the coal and B. subtilis. (C) 2013 Elsevier B.V. All rights reserved.