High magnetic field enhances stationary phase-specific transcription activity of Escherichia coli

When Escherichia coli B was aerobically grown at 37°C under inhomogeneous 5.2–6.1 Tesla (T) magnetic fields in the superconducting magnet biosystem (SBS), the cell number in the stationary phase after the growth had leveled off, was about 3 times higher than that under a geomagnetic field. When the E. coli defective in the rpoS gene which encodes a sigma factor, σ^s of RNA polymerase and is specifically expressed in the stationary phase was cultivated at 37°C in SBS, such enhancement of cell survival was significantly reduced. The E. coli cells carrying rpoS–lacZ fusion gene or other rpoS dependent genes fused with lacZ were grown, significant increase in the activity of β-galactosidase was observed in the stationary phase under high magnetic field. These data suggest that enhancement of the transcription activity in stationary phase is involved in the higher survival of the cells under magnetic field.