Effect of ELF magnetic fields on protein synthesis in Escherichia coli K12

Escherichia call K12 was used as a model system to determine whether ELF ma gnetic fields (MFs) are a general stress factor. The cells were exposed to ELF MFs (5-100 Hz) at a maximum intensity of 14 mT r.m.s. for circularly po larized MFs and 10 mT r.m.s. for vertically polarized MFs. The response of the cells to the MFs was estimated from the change in protein synthesis by using 2D PAGE. Approximately 1,000 proteins were separated on the 2D gels. The stress-responsive proteins such as CH10, DNAK, CH60, RECA, USPA, K6P1 a nd SODM were identified from the SWISS-2DPAGE database on the 2D gels. Thes e proteins respond to most stress factors, including temperature change, ch emical compounds, heavy metals, and nutrients. hen the bacterial cells were exposed to each MF at 5-100 Hz under aerobic conditions (6.5 h) or at 50 H z under anaerobic conditions (16 h) at the maximum intensity (7.8 to 14 mT r.m.s.), no reproducible changes were observed in the 2D gels. Changes in p rotein synthesis were detected by 2D PAGE with exposure to heat shock (50 d egrees C for 30 min) or under anaerobic conditions (no bubbling for 16 h). Increases in the levels of synthesis of the stress proteins were observed i n heat-shocked cells (CH60, CH10, HTPG, DNAK, HSLV, IBPA and some unidentif ied proteins) and in cells grown under anaerobic conditions (DNAK, PFLB, RE CA, USPA and many unidentified proteins). These results suggest that 2D PAG E is sufficient to detect cell responses to environmental stress. The high- intensity ELF MFs (14 mT at poser frequency) did not act as a general stres s factor. (C) 2000 by Radiation Research Society.