Study Of Bio-effect Of ELF-EMF On Bacteria's Biological Characteristics And Potential Mechanism

Extremely low frequency magnetic field ( ELF-EMF ), one of the environmental factors, widely exists in our daily life. However, the interaction between ELF-EMF and biological materials was still unclear thought a lot of research has been done. The research has positive significance for us to get more information about ELF-EMF biological effects and reveal its underlying mechanism.Bio-effect of ELF-EMF ( 50 Hz, 1⁵ mT ) on bacteria was studied in this thesis. Growths inhibition and cytotoxicity was observered after E.coli was exposure to 50 Hz electromagnetic fields. There was a cooperative effect between ELF-EMF and other environment factors such an UV, Pb2+ and phenol. To elucidate this cooperative effect, those factors' pathway and thire possible mechanism were discussed. The main research conclusion was drawed as follow:(1) ELF-EMF's biological effects were dependent on exposure intensity and exposure time. In addition, nonlinear relationship was appared in inhibitory effect. And saturation phenomenon emergenced in certain exposured time. After exposured to 50 Hz, 1 mT electromagnetic fields, a significant growth inhibited effect appeared in both continual stimulation and intermittent stimulation. Meanwhile, continual stimulation showed a higher inhibited effect than intermittent stimulation.(2) Cells of different phase of bacterial growth shows a different sensitive to ELF-EMF. And cells in logarithmic phase were most sensitive to ELF-EMF. In addition, different microorganisms have different sensitivities to the same ELF-EMF. E.coli is most sensitive and vulnerable.(3) Potential genotoxic was appeared in long time ELF-EMF exposured. And DNA damaged was observed after Salmonella typhimurium TA 1535 was exposured to 50 Hz, 3 mT ELF-EMF for more than 18 h. In addition, genotoxicity was examined after E.coli was exposured to 50 Hz, 3 mT ELF-EMF for 14 h. While exposured time prolong to 18 or 24 h, the genotoxicity become significant. ELF-EMF changed the protein expression when E.coli exposured to 50 Hz, 3 mT ELF-EMF for more than 24 h. A molecular which is about 60 kDa was observed after 24 h ELF-EMF exposured. And it was speculated as small heat shock proteins.(4) Synergy effect between ELF-EMF and Pb²⁺ or phenol was reported. The susceptibility thresholds of E.coli to Pb²⁺ and phenol were significantly reduced by 50 Hz, 3 mT ELF-EMF. Finally, RCFE was lower while E.coli cells exposured to UV followed ELF-EMF rather than exposured to ELF-EMF followed by UV exposured.