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

Investigation of Escherichia coli under electromagnetic fields is of significance in human studies owing to its short doubling time and human-like DNA mechanisms. The present review aims to systematically evaluate the literature to conclude causality between 0 and 300 GHz electromagnetic fields and biological effects in E. coli. To that end, the OHAT methodology and risk of bias tool were employed. Exponentially growing cells exposed for over 30 min at temperatures up to $37^{\circ }C$ with fluctuations below $1^{\circ }C$ were included from the Web-of-Knowledge, PubMed, or EMF-Portal databases. Out of 904 records identified, 25 articles satisfied the selection criteria, with four excluded during internal validation. These articles examined cell growth (11 studies), morphology (three studies), and gene regulation (11 studies). Most experiments (85%) in the included studies focused on the extremely low-frequency (ELF) range, with 60% specifically at 50 Hz. Changes in growth rate were observed in 74% of ELF experiments and 71% of radio frequency (RF) experiments. Additionally, 80% of ELF experiments showed morphology changes, while gene expression changes were seen in 33% (ELF) and 50% (RF) experiments. Due to the limited number of studies, especially in the intermediate frequency and RF ranges, establishing correlations between EMF exposure and biological effects on E. coli is not possible.