In this study, the fluorescent protein MagLOV2 was characterized for how its brightness changes depending on the strength of an applied external magnetic field in living bacterial cells. At very low magnetic field strengths, fluorescence increases as the field becomes stronger. However, at moderately higher field strengths, the trend reverses, and the fluorescence decreases with further increases in the magnetic field before eventually leveling off. This complex response is consistent with established models of a process known as the “radical pair mechanism”, which is a leading hypothesis for how biological molecules can be affected by weak magnetic fields. The results suggest that the sensitivity of MagLOV2 to magnetic fields is consistent with an underlying quantum mechanism that operates in the complex environment of a living cell.

Despite decades of reports of weak magnetic field effects in biology across the tree of life and on a broad range of cell types, the evidence to date remains met with skepticism. To remedy this, we present open-data, large-scale, and varied morphological evidence that Xenopus laevis embryo development is accelerated in a well-engineered, environmentally-calibrated hypomagnetic field of less than 1 nT. These data imply that basal tadpole physiology can sense and react to the absence of Earth’s minute magnetic field of approximately 50 μT. The effect is significant, as demonstrated by a variety of statistical measures. As no definitive biophysical mechanism has been identified to account for its occurrence, this study raises the question of which mechanism provides the most plausible explanation. How that question is answered may have implications in a variety of fields, including human health, behavioral ecology, and space exploration.