Low-frequency magnetic fields induce oxidative and genotoxic stress and growth stimulation in lactic acid bacteria

Low-frequency magnetic fields are increasingly encountered in environmental and industrial settings, yet their biological effects on probiotic lactic acid bacteria (LAB) remain incompletely characterized. This study evaluated the impact of direct current (DC) and alternating current (AC) magnetic fields on growth, redox homeostasis, and genomic integrity in representative LAB strains.

Lactobacillus acidophilus, Lactobacillus bulgaricus, Lactobacillus rhamnosus, Lactobacillus pentosus, Lactobacillus casei, and Lacticaseibacillus paracasei were exposed to DC and AC magnetic fields. Bacterial growth was assessed by optical density. Oxidative stress parameters-including total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), intracellular glutathione (GSH), and malondialdehyde (MDA)-were quantified, and genotoxicity was evaluated using DNA fragmentation assays and DNA absorbance at 260 nm.

Type III two-way ANOVA identified magnetic field intensity as the dominant determinant of bacterial responses, with significant effects in 41 of 48 models, whereas magnetic field type was significant in 28 models and field type × intensity interactions in 18 models. Increasing field intensity significantly altered culture turbidity (OD600), TOS, OSI, GSH, MDA, DNA fragmentation, and DNA absorbance at 260 nm across most bacterial species (p < 0.05). Oxidative stress biomarkers exhibited the largest effect sizes (partial η² frequently > 0.90), while significant interaction effects were observed predominantly for TOS and OSI, indicating species-dependent differences between AC and DC exposure. Overall, oxidative stress was strongly associated with DNA damage and alterations in bacterial growth.

Low-intensity AC and DC magnetic fields induced significant oxidative and genotoxic responses that were governed primarily by magnetic field intensity rather than field type. The predominance of oxidative stress-related effects, together with their strong association with DNA damage, suggests that redox imbalance represents the principal mechanism underlying bacterial responses to magnetic field exposure. These findings indicate that probiotic lactic acid bacteria retain short-term physiological tolerance while exhibiting increased DNA fragmentation and evidence of altered genomic integrity at higher magnetic field intensities.