E. coli cells when placed under extremely low frequency (ELF) magnetic field sine wave of 30 pT at 9 Hz, exhibited a change in the conformational state of the genome, which was maximum at 4 x 108 cells mL-1 while there was no such response at lower cell densities of 3 x 105 cells mL-1. Other than cell density, time of exposure also affected genomic conformation. The change in the conformational state of the genome is considered to be dependent on DNA parameters, i. e. molecular weight and the number of proteins bound to the DNA [9]. Thus the ELF field which is close to the ion cyclotron resonance parameters for a medium weight ion might be influencing these factors that ultimately elicit response on the conforma­tion. It was also proposed that the possibility of a resonance fluorescence effect where recombination of fluorescing radicals may act as signals for intercellular communication and participate in the synchronization of gene expression. Weak, static magnetic fields (0-110 pT) are shown affecting DNA-protein conformations in E. coli. The analysis by Binhi et al. [51] represented a dose-response curve for the static magnetic field. The curve however is peculiar in having three prominent maxima unlike other dose — response curves in nature that usually follow rising or decaying exponen­tial functions. They explained this peculiarity in the context of the ion interference mechanism. No alteration in the profile of stress proteins of E. coli was observed by Nakasono et al. [52] on exposure to AC fields (7.8-14 mT, 5-100 Hz). In Saccharomyces cerevisiae no changes were observed under AC magnetic fields (10-300 mT, 50 Hz) in differential gene expression and protein profile that were determined using microar­ray and 2-D protein profile analysis, respectively [53]. But, Gao et al. [54] reported that strong magnetic fields (14.1 T) could lead to transcriptional up-regulation of 21 genes and down-regulation of 44 genes in a gram­negative anaerobic bacterium Shewanella oneidensis that did not show any significant effect on growth. In the anoxygenic photosynthetic bacte­rium, Rhodobacter sphaeroides, AC magnetic fields of 0.13-0.3 T induced a 5-fold increase in porphyrin synthesis, and enhanced expression of the enzyme 5-aminolevulinic acid dehydratase, while very strong DC fields (0.13-0.3 T) also induced synthesis of this enzyme predominantly at the magnetic North Pole. The effects are attributed to elevated gene expres­sion that ultimately resulted in increased porphyrin production [25].

Mitotic delay of 0.5 to 2 h was observed in a slime mold Physarum polycephalum in presence of ELF electromagnetic fields (45, 60 and 75 Hz) by Goodman et al. [44]. Removal of the mold from magnetic field recovered normal mitosis in 40 days.