Effect of high magnetic field on the growth of Bacillus subtilis measured in a newly developed superconducting magnet biosystem

A new superconducting magnet biosystem (SBS) has been developed, which can provide a magnetic field of 0.5-7 T, where biological reactions can be conducted under temperature-controlled conditions. The aerobic growth of a bacterium, Bacillus subtilis MI113, was investigated under homogeneous (7 T) and inhomogeneous (5.2-6.1 T) magnetic fields in a shaken culture. In the stationary phase, the cell number in an inhomogeneous magnetic field was about twofold higher than that of the reference, indicating that the magnitude of the decrease in the cell number was reduced by the high magnetic field. The slower decline in the cell number in a magnetic field was due to the slower death rate of the vegetative cells. The inhibition of spore formation from vegetative cells was also observed in a magnetic field, which was reflected by the reduced activity of aikaline phosphatase. Genetically transformed B. subtilis MI113 (pC112) produced a higher concentration of a lipopeptide antibiotic, surfactin, in the stationary phase in an inhomogeneous magnetic field due to the higher cell number of the transformant in the magnetic field. (C) 1997 Elsevier Science S.A.