Effect of extremely low frequency electromagnetic fields on growth rate and morphology of bacteria.

Abstract

PURPOSE: To determine the effect of extremely low frequency (<300 Hz) electromagnetic fields (ELF-EMF) on the growth rate of Gram-positive and Gram-negative bacteria and to determine any morphological changes that might have been caused by ELF-EMF. MATERIALS AND METHODS: Six bacterial strains, three Gram-negative and three Gram-positive were subjected to 50 Hz, 0.5 mT ELF-EMF for 6 h. To determine growth rate after ELF-EMF application, bacteria exposed to ELF-EMF for 3 h were collected, transferred to fresh medium and cultured without field application for another 4 h. Growth-rate was determined by optical density (OD) measurements made every hour. Morphological changes were determined with Transmission electron microscopy (TEM) for two gram-negative and two gram-positive strains collected after 3 h of field application. RESULTS: A decrease in growth rate with respect to control samples was observed for all strains during ELF-EMF application. The decrease in growth-rate continued when exposed bacteria were cultured without field application. Significant ultrastructural changes were observed in all bacterial strains, which were seen to resemble the alterations caused by cationic peptides. CONCLUSION: This study shows that ELF-EMF induces a decrease in growth rate and morphological changes for both Gram-negative and Gram-positive bacteria.

AI evidence extraction

Main findings

All six bacterial strains showed decreased growth rate compared with controls during 50 Hz, 0.5 mT ELF-EMF exposure, and the decrease continued after transfer to fresh medium and culture without field application. Significant ultrastructural changes were observed in all strains by TEM after 3 h exposure.

Outcomes measured

• Bacterial growth rate (optical density measurements)
• Bacterial morphology/ultrastructure (TEM)

Limitations

• In vitro bacterial study; findings may not generalize beyond the tested strains/conditions
• Only one frequency (50 Hz) and one magnetic flux density (0.5 mT) tested
• Morphology assessed by TEM in a subset of strains (two Gram-negative and two Gram-positive)

{
    "study_type": "in_vitro",
    "exposure": {
        "band": "ELF",
        "source": null,
        "frequency_mhz": 5.00000000000000023960868011929647991564706899225711822509765625e-5,
        "sar_wkg": null,
        "duration": "6 h (growth); 3 h exposure then 4 h culture without field (growth follow-up); 3 h exposure (TEM)"
    },
    "population": "Six bacterial strains (three Gram-negative, three Gram-positive)",
    "sample_size": 6,
    "outcomes": [
        "Bacterial growth rate (optical density measurements)",
        "Bacterial morphology/ultrastructure (TEM)"
    ],
    "main_findings": "All six bacterial strains showed decreased growth rate compared with controls during 50 Hz, 0.5 mT ELF-EMF exposure, and the decrease continued after transfer to fresh medium and culture without field application. Significant ultrastructural changes were observed in all strains by TEM after 3 h exposure.",
    "effect_direction": "harm",
    "limitations": [
        "In vitro bacterial study; findings may not generalize beyond the tested strains/conditions",
        "Only one frequency (50 Hz) and one magnetic flux density (0.5 mT) tested",
        "Morphology assessed by TEM in a subset of strains (two Gram-negative and two Gram-positive)"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "extremely low frequency",
        "ELF-EMF",
        "50 Hz",
        "0.5 mT",
        "bacteria",
        "Gram-negative",
        "Gram-positive",
        "growth rate",
        "optical density",
        "transmission electron microscopy",
        "ultrastructural changes"
    ],
    "suggested_hubs": []
}

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