# Effects of Resonant Electromagnetic Fields on Biofilm Formation in _Pseudomonas aeruginosa_
## 4 Discussion  
The aim of this study was to establish a bioresonance laboratory and explore the use of weak resonant electromagnetic fields as a method to disrupt biofilm formation in vitro of a known pathogenic bacterium, _Pseudomonas aeruginosa_. _P. aeruginosa_ is a pathogen that is dominant in patients suffering from cystic fibrosis and any new approach to inhibit the infectious biofilm formation of this bacterium in the lungs of CF patients would be highly important and have clinical relevance. In summary, the following three results were obtained: (1) no effects of a shielded or specific magnetic field on the growth of planktonic, i.e., non-biofilm forming bacteria, (2) a variable or non-constant effect of the ambient or environmental electromagnetic field on bacterial biofilm formation, and (3) an inhibitory effect on bacterial biofilm formation at a specific frequency of the electromagnetic field. Figure 4: Effect of shielded vs. exposed conditions on biofilm adhesion units (ratios of OD590/OD600) normalized to control condition “Zero/Shielded”. Data points from six experimental series (A–G) are shown at two different conditions: “Zero/shielded” and “Exposed/3.9 Hz”. Y-axis show normalized values relative to the “Zero/shielded” condition (value 100). Standard deviation for each microtiter plate and statistical _p_-values (paired _t_-test) are indicated (*****  
With regard to the first finding, it has been reported by others that electrical and magnetic fields may affect planktonic bacterial growth (see [28] and references therein). However, in the present study, no such effect was observed. It might be argued that OD600 does not necessarily correspond to the number of viable bacteria and could also include dead cells. However, a few live/dead stains and growth curves were performed non-systematically, which indicated that there were no differences between the experimental conditions and that planktonic bacterial cultures were growing as expected. The second finding related to the ambient electromagnetic field. When looking at the ability to form biofilm on the peg-lids, it was found that the ambient or environmental electromagnetic field in our research facility did have a non-constant effect on bacterial biofilm formation. Thus, the ambient electromagnetic field caused by natural and artificial phenomena, cannot be assumed to be constant from one experimental period to the other. For example, in any modern-day laboratory setting, electrical equipment such as refrigerators, telecommunication equipment, etc., may produce a non-negligible 50 Hz magnetic field of 500 nanoT or more. It is therefore important to control for this using, for example, a mu-metal cylinder shielding against the ambient magnetic fields. Studying formation of bacterial biofilm as opposed to planktonic growth can be challenging, since biofilm can form on most surfaces that a bacterial culture touches. In the case of standard microtiter plates, the bottom, sides, and rim surfaces are subject to biofilm formation. This presented a great challenge to early investigations of microbial biofilm formation, since it was very difficult to separate the planktonic and attached fractions in a standard well or dish. In 1999, the peg-lid principle was introduced, which showed much improved reproducibility, due to the ability to easily separate a defined portion of the surface available (the pegs) to the bacteria [29]. Furthermore, the use of the 96-well microtiter format basically allows for performing 96 technical replicates in one batch, and thus improving the statistical power greatly. The third finding in this study was based on using the proper control and a statistically robust biological peg-lid assay as described above. Using a magnetically shielded bacterial culture as control, it was found that exposing the bacteria to a specific electromagnetic field of 10 microT and 3.9 Hz consistently showed an inhibitory and statistically significant reduction of biofilm formation.