Medical/biological study (experimental study)

Bacterial response to the exposure of 50 Hz electromagnetic fields med./bio.

By: Cellini L, Grande R, Di Campli E, Di Bartolomeo S, Di Giulio M, Robuffo I, Trubiani O, Mariggio MA

Published in: Bioelectromagnetics 2008; 29 (4): 302-311

Aim of study (acc. to author)

To study the ability of microorganisms to activate strategies in adapting themselves to the environmental stress induced by exposure to extremely low frequency electromagnetic fields, cultures of Escherichia coli were exposed at 50 Hz (0.1, 0.5, 1.0 mT).

Background/further details

Culture samples were exposed for 20 min. (acute exposure) or 120 min (about 6 generations, chronic exposure) and replaced outside of the switched off solenoid in the incubator for 24 h with an electromagnetic field background of 100 nT (50 Hz). Five independent experiments were performed and each experiment in triplicate.

Endpoint

cell viability/cell division/proliferation: bacterial cell viability and counts

Exposure

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: continuous for 20 or 120 min	magnetic flux density: 0.1 mT minimum (+/- 2 %) magnetic flux density: 0.5 mT (+/- 2 %) magnetic flux density: 1 mT maximum (+/- 2 %)

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	sinusoidal
Exposure duration	continuous for 20 or 120 min

Exposure setup

Exposure source	coil(s) solenoid
Setup	cells in glass flasks located on a non-magnetic support inside the coil in the maximum homogenity part of the magnetic field
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	0.1 mT	minimum	measured	-	+/- 2 %
magnetic flux density	0.5 mT	-	measured	-	+/- 2 %
magnetic flux density	1 mT	maximum	measured	-	+/- 2 %

Exposed system:

bacterium
Escherichia coli/ATCC 700926

Methods Endpoint/measurement parameters/methodology

genotoxicity/mutation: genotypical and transcriptional profiles/fingerprints (DNA/RNA-AFLP)
cell viability/cell division/proliferation: bacterial cell viability and counts (total and culturable; optical density, colony count/CFU); antimicrobial susceptibility pattern (disc diffusion test); morphological analysis (optic microscopy and transmission electron microscopy)

Investigated system:

DNA/RNA
bacterium
ultrathin sections

Time of investigation:

before exposure
after exposure

Main outcome of study (acc. to author)

Exposed and sham exposed samples showed similar cell counts, whereas an increased cell viability was observed in exposed samples re-incubated for 24 h outside of the solenoid compared to the corresponding controls.
An exposure of 20-120 minutes produced a significant change of morphotype with a presence of coccoid cells also aggregated in clusters after re-incubation of 24 h outside of the solenoid. Atypical lengthened bacterial forms were also found.
No changes among genotypical and transcriptional profiles were found for each electromagnetic field intensities evaluated.
The data indicate that an exposure to 50 Hz electromagnetic field acts as a stress factor on bacteria which can represent a suitable model to study acute and chronic effects related to extremely low frequency electromagnetic field exposure.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Ministero dell'Ambiente e della Tutela del Territorio e del Mar (Ministry of Environment and Territory), Italy

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