Study type: Medical/biological study (experimental study)

Genome-wide transcription analysis of Escherichia coli in response to extremely low-frequency magnetic fields. med./bio.

Published in: Bioelectromagnetics 2012; 33 (6): 488-496

Aim of study (acc. to author)

To study the transcription (gene expression) of Escherichia coli in response to extremely low frequency magnetic fields.

Background/further details

Samples were withdrawn before and after inoculation at the end of the batch culture growth, about 3 h before reaching the stationary growth, at stationary growth, and at three different time points after initiating magnetic field exposure or sham exposure (8 min (except for field 2), 2.5 h and 15 h).
Hydrogen peroxide was used to induce oxidative stress (positive control). Negative controls were also included. Each experiment consisted of three independent replicates.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Exposure duration: continuous for 15 h
sinusoidal continuous signal
Exposure 2: 50 Hz
Exposure duration: intermittent: 2 min on, 4 min off, for 15 h
Exposure 3: 50 Hz
Exposure duration: intermittent: 2 min on, 4 min off, for 15 h

Exposure 1

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous for 15 h
Additional info sinusoidal continuous signal
Additional info ramp amplitude function used for signal
Exposure setup
Exposure source
Chamber two metal chambers were used containing a bifilar coil system; two parallel operating chemostats (250 ml bioreactor, 35 mm diameter), each with a volume of 100 ml were put in their own exposure chamber and run side-by-side in a standard incubator; bioreactors were placed in the center of the coils
Sham exposure A sham exposure was conducted.
Additional info temperature inside the two bioreactors was 35.7°C
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT peak value measured and calculated - within the box containing the bioreactor

Exposure 2

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration intermittent: 2 min on, 4 min off, for 15 h
Additional info sinusoidal intermittent signal
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT peak value measured and calculated - within the box containing the bioreactor

Exposure 3

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration intermittent: 2 min on, 4 min off, for 15 h
Additional info power line intermittent signal
Additional info the power line signal represents the maximal accepted distortion regarding spectral components for low- and medium-voltage power systems, as defined by the International Electrotechnical Commission (IEC).
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT peak value measured and calculated - within the box containing the bioreactor

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • before exposure
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

For all three types of magnetic fields investigated, neither bacterial growth (measured by optical density) nor culturable colonies (CFU) were affected. Likewise, no statistically significant change in the expression of 4358 genes and 714 intergenic regions was detected after magnetic field exposure for 2.5 h or 15 h. Moreover, short-term exposure (8 min) to the sinusoidal continuous and power line intermittent signal (fields 1 and 3) neither affected bacterial growth nor showed evidence for reliable changes in transcription.
In conclusion, the data did not indicate that the different magnetic fields (50 Hz, 1 mT) affected the transcription of Escherichia coli.

Study character:

Study funded by

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