The effect of week static magnetic fields on Escherichia coli K12 AB1157 cells was studied by the method of anomalous viscosity time dependencies (AVTD). The AVTD changes were found when E. coli cells were exposed to static fields within the range from 0 to 110 μT. The dependence of the effect on the magnetic flux density had several extrema. These results were compared with theoretical predictions of the ion interference mechanism. This mechanism links the dissociation probability of ion–protein complexes to parameters of magnetic fields. The mechanism was extended to the case of rotating complexes. Calculations were made for several ions of biological relevance. The results of simulations for Ca²⁺, Mg²⁺, and Zn²⁺ showed a remarkable consistency with experimental data. An important condition for this consistency was that all complexes rotate with the same speed ∼18 revolutions per second (rps). This suggests that the rotation of the same carrier for all ion–protein complexes may be involved in the mechanism of response to the magnetic field. We believe that this carrier is DNA. Bioelectromagnetics 22:79–86, 2001. © 2001 Wiley‐Liss, Inc.