Escherichia coli K12 exhibits a ~50% longer lag phase, but no difference in log phase growth rate, under hypomagnetic conditions (19 nT)

Previous investigations have explored the effects of hypermagnetic fields, that is, fields in excess of the Earths background geomagnetic field strength of approximately 50 {micro}T, on Escherichia coli (E. coli). Conversely, this study investigates the effects of hypomagnetic field conditions, that is, fields below the geomagnetic background intensity, on the growth of E. coli K12 by using a hypomagnetic chamber to shield cultures, with a measured residual magnetic field inside the chamber of 19 nT. When grown in rich media from a semi-anaerobic, stationary-phase starting culture under geomagnetic and hypomagnetic conditions, the lag phases of E. coli were approximately 86 minutes and 132 minutes, respectively. Despite this increase in lag phase, exceeding two E. coli doubling times, the log-phase growth rate of E. coli was identical under both geomagnetic and hypomagnetic conditions. In addition to demonstrating a biologically relevant sensitivity to magnetic field parameters in the hypomagnetic direction, this represents a much greater absolute magnetosensitivity, with a deviation of only 50 {micro}T between the hypomagnetic and geomagnetic conditions, than has previously been demonstrated for E. coli.