Abstract
Magnetobiological effects on growth and virulence have been widely reported in Escherichia coli (E. coli). However, published results are quite varied and sometimes conflicting because the underlying mechanism remains unknown. Here, we reported that the application of 250 mT static magnetic field (SMF) significantly reduces the diameter of E. coli colony-forming units (CFUs) but has no impact on the number of CFUs. Transcriptomic analysis revealed that the inhibitory effect of SMF is attributed to differentially expressed genes (DEGs) primarily involved in carbon source utilization. Consistently, the addition of glycolate or glyoxylate to the culture media successfully restores the bacterial phenotype in SMF, and knockout mutants lacking glycolate oxidase are no longer sensitive to SMF. These results suggest that SMF treatment results in a decrease in glycolate oxidase activity. In addition, metabolomic assay showed that long-chain fatty acids (LCFA) accumulate while phosphatidylglycerol and middle-chain fatty acids decrease in the SMF-treated bacteria, suggesting that SMF inhibits LCFA degradation. Based on the published evidence together with ours derived from this study, we propose a model showing that free radicals generated by LCFA degradation are the primary target of SMF action, which triggers the bacterial oxidative stress response and ultimately leads to growth inhibition.
Highlights
The Earth has been generating a weak static magnetic field (SMF), named the geomagnetic field (GMF), with an intensity around 50 μT at the surface for more than 4 billion years [1,2]
Our results showed that the size of the colony-forming units (CFUs) treated with SMF was apparently smaller than that of the control (Figure 1C), in spite of there being no difference in the number of CFUs between SMF-treated and control bacteria (Figure 1D)
We examined the dose-dependent effect of SMF on bacterial growth by adjusting the distance from the magnet to the bottom of the petri dish
Summary
The Earth has been generating a weak static magnetic field (SMF), named the geomagnetic field (GMF), with an intensity around 50 μT at the surface for more than 4 billion years [1,2]. Evidence is increasing to show that GMF can function as signals to help various organisms adapt to environmental changes and/or as energy to randomly affect biochemical reactions [3–6]. Single-cell microorganisms are extensively utilized to study series of magnetobiological effects and the underlying molecular mechanisms. It is hard to have common views on the nonspecific magnetobiological effects on microbe growth and the underlying mechanisms due to the diversity, complexity and inconsistency of the published data [9]. SMF effects are liable to be altered by many factors related to experimental designs, such as SMF intensity and gradients, bacterial strains, treatment time and culture conditions, and to dynamic intracellular and extracellular targets of SMF [10,11]. Because bacteria exist ubiquitously in our surroundings and bodies, understanding the biological effects of SMF on bacteria will make a significant contribution to improving our environment, sanitation and health
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
