Effects of low-frequency magnetic fields on bacterial growth rate.

A large number of cultures of the bacterium E. coli have been grown in weak alternating magnetic fields of square waveform, at frequencies of 50 Hz and 16.66 Hz. Control cultures were simultaneously grown under ambient conditions identical except for the almost complete absence of any magnetic field. The mean generation time (MGT) for a culture subjected to alternating magnetic fields is significantly reduced by comparison with that for the control cultures. Application of the F-ratio test indicates a probability of less than one in two million that the effects observed are due to chance. A marked threshold effect is observed, along with strong indications of periodicity in the graph of MGT against magnetic field strength. Within the limits of experimental error, these effects correspond to integral changes in the number of magnetic flux quanta linking an individual bacterial cell during the process of division.