Study On The Mechanism Of Static Magnetic Field Affecting Microbial Growth

Geomagnetic field(GMF)is indispensable for all organisms living on the earth,because it protects the earth's ecosystem from the direct harm of solar wind and other cosmic rays and affects the vital activities of organisms as a physical environment factor.Many researches shows that magnetic field has multiple effects on behavioral characteristics,physiological reactions,metabolism and gene expression of organisms,however,biological significance and molecular mechanisms underlying magnetic field action remain unclear.Here,we explore the molecular mechanisms of static magnetic field(SMF)action by using bacteria,the simple biological model.We used Escherichia coli(E.coli)as material to explore the effects of moderate static magnetic field on bacteria survival and growth.We found that the application of250 m T static SMF significantly reduces the diameter of E.coli colony-forming units(CFUs)but has no impact on the number of CFUs.Transcriptomic analysis showed that about 5% genes(202 of 4081)changed their expression quantities,and 145 genes were downregulated while 54 were upregulated in SMF treatment group.Further 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.In addition,we explored the effects of SMF on mice gut microbiota using 16 S rRNA gene sequencing analysis.Our results showed that 600 m T SMF treatment for 8weeks significantly affected the relative abundances of mice intestinal microbes,and different strains had different responses to SMF.Among the bacterial which had significant differences in relative abundances,we noticed an unidentified strain unclassified?g??Escherichia-Shigella had a decreased relative abundance,which had similar phenotype with E.coli that was pure cultured in250 m T SMF.These results indicate that SMF can indeed affect the composition of intestinal microbiome in mice.However,more experiments are needed to further explain the effect of SMF on the composition of intestinal microbiome due to the complexity of the factors.