A systematic review on cellular responses of Escherichia coli to nonthermal electromagnetic irradiation

Authors: Askaripour K, Zak A

Year: 2024 Jan

Category: Bioelectromagnetics, Cellular Biology, Systematic Review

Journal: Bioelectromagnetics

DOI: 10.1002/bem.22484

Abstract

Overview

Investigation of Escherichia coli under electromagnetic fields (EMFs) is significant due to its short doubling time and similarities in DNA mechanisms with humans. This systematic review aims to thoroughly evaluate the existing literature to determine if there is a causal relationship between nonthermal electromagnetic radiation (AC, 0–300 GHz) and biological effects in E. coli.

Methodology

  • Systematic review was conducted using OHAT methodology and a risk of bias tool.
  • Studies involving exponentially growing E. coli exposed to EMF (0–300 GHz) for at least 30 minutes, with controlled temperature conditions, were included.
  • Out of 904 records identified, 25 articles met inclusion criteria, with four excluded during validation, resulting in 21 studies included for evidence synthesis.

Findings

  • Most experiments (85%) targeted the extremely low-frequency (ELF) range, with 60% specifically at 50 Hz.
  • Nonthermal EMF exposure effects on E. coli were observed as follows:
    • Growth rate: Effects present in 74% of ELF and 71% of RF experiments.
    • Cell morphology: Changes observed in 80% of ELF experiments.
    • Gene expression: Changes in 33% (ELF) and 50% (RF) of experiments.
  • Reliability of results is strongest for ELF-EMF, mainly at 50 Hz, due to the limited number of studies on intermediate and radiofrequency ranges.
  • Exposure conditions such as intensity, frequency, and modulation (e.g., pulsed vs. continuous signals) significantly influenced biological outcomes, producing either beneficial or detrimental effects.
  • About 16 of 38 experiments showed detrimental growth effects, highlighting the potential for harm under certain EMF exposures.

Risks & Limitations

  • Lack of sufficient and clear exposure reporting impedes direct comparison between studies.
  • Potential risk of bias exists due to variability in research design, exposure randomization, blinding, and allocation concealment.
  • Research gaps exist in mechanistic studies and intermediate/radiofrequency ranges.

Conclusion

The review finds that nonthermal electromagnetic fields, especially those in the ELF and RF range, can alter cell growth, morphology, and gene expression in E. coli. While a conclusive correlation has not been fully established due to study limitations, a clear link exists between EMF exposure and biological responses in bacterial cells. Considering the genetic and mechanistic parallels with human biology, these findings underline the importance of investigating EMF exposure risks for human health. Continued research is essential to clarify the mechanisms and long-term implications.

electromagnetic fields nonthermal effects Escherichia coli ELF-EMF radiofrequency gene expression cell growth
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