Abstract: Method of exciting an electro-magnetic mechanical resonance in a structural component (2, 3) of a microorganism (1), the method comprising exposing said microorganism to an oscillating magnetic field (H), which oscillates at least at a first frequency, characterized in that said first frequency corresponds to a frequency of a mechanical resonance of said structural component. The invention is further directed to a method of selecting effective operating parameters to perform the invention. Under further aspects, the invention relates to applications of the method in in the technical fields of water treatment, nutrition industry, cell culture industry or paper industry as well as in the general reduction or limitation of the reproduction of specific germs in all areas, as well as in human and animal tissue cultures, ex vivo (extracorporal) of blood preparations.