EL-SAYED A. GAAFAR*, MAGDA S. HANAFY**, EMAN Y. TOHAMY***, MONA H. IBRAHIM**

*Biophysics Department, Faculty of Science, Cairo University, Egypt
**Physics Department, Faculty of Science, Zagazig University, Egypt
***Botany Department, Faculty of Science, Zagazig University, Egypt

Abstract. The effect of a 50 Hz magnetic field of strength 2 mT on each of the growth characteristics, the antibiotic sensitivity and the ultra structure of E. coli bacteria cells have been studied. Equal volumes of E. coli cells were exposed to the magnetic field for different periods, the two most effective periods, namely, 6 h and 16 h were chosen for all our experimental studies. The results indicated that exposure of the microorganisms to the demonstrated magnetic field caused pronounced changes in the growth characteristic curves, where a suppressive effect was observed on the cell growth and the number of cells at stationary phase markedly decreased after exposure period of 6 h but there was a slight increase in the growth rate after exposure period of 16 h with increase in the number of cells. Further, changes in the antibiotic sensitivity was observed after exposure period of 6 h since E. coli cells became more sensitive to certain antibiotics such as amoxicillin, nalidixic acid and erythromycin as revealed in the increase in their zone diameters while, after a 16 h exposure period, it became more resistant to the same antibiotics. Furthermore, the results of the ultra structure showed that while exposure period 6 h decreased the cell length, the exposure period 16 h elongated the cell length with decreasing the thickness of the cell wall beside the disappearance of the majority of cytoplasmic components.
Keywords: electromagnetic field, E. coli, growth rate, antibiotic sensitivity, ultra structure.

Corresponding author’s e-mail: ashruf_hilal@hotmail.com

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