Toward a better understanding of the microbial growth inhibition by electromagnetic fields

Published : 2 February 2017

                                   Logo_IMEP-LAHC                   Master thesis proposal – MARCH to JULY 2017        

Toward a better understanding of the microbial growth inhibition by electromagnetic fields

Keywords :
Electromagnetism, microbial decontamination, growth inhibition mechanisms, numerical modeling

Labs :
Institut de Microélectronique, Electromagnétisme et Photonique- Laboratoire d’Hyperfréquences et de Caractérisation (IMEP-LaHC)
Minatec – 3, parvis Louis Néel, BP 257
38 016 GRENOBLE Cedex 1, FRANCE

Institut des Géosciences de l’Environnement (IGE, UGA-CNRS-IRD-G-INP)
70 rue de la Physique, Bâtiment OSUG B , BP 53
38 041 GRENOBLE Cedex 09, FRANCE

Directors :
XAVIER Pascal,, +33 (0)
MARTINS Jean,, +33 (0)

Required skills and level of the applicant :
Master in biomedical or biophysical engineering. Some work experience in electronics are also desired.

 Scientific context and objectives
In the battle against pathogenic microorganisms, in addition to the oldest curative process of pasteurization (heating) requiring large quantities of energy, current methods are mechanical actions (brushing) and the action of chemical products: acetic acid, hydrogen peroxide, chlorine dioxide… For example, the cheese industry is one of the largest users of chlorine. Unfortunately, some strains have become very resistant.
The use of physical means for the decontamination of water has only been explored for less than a century. Low intensity DC or AC current has been proven to be effective. This process was reported more than fifty years ago. Most articles in the literature focus on improving the effectiveness of antibiotics against microorganisms by applying weak currents, a phenomenon called “bioelectric effect” (Blenkinsopp 1992, Costerton 1994, Giladi 2008).
Several mechanisms have been proposed for this inhibition: electrolysis, production of toxic derivatives and free radicals linked to the electrodes, modification of the pH. In addition, the application of a high amplitude pulsed electric field has been used as a non-thermal effect for the inhibition of bacterial growth with the major disadvantage of the phenomenon of electroporation.
High-frequency electromagnetic fields (above MHz) but with small amplitudes (<1 V / cm) have also been reported as a means to improve the susceptibility of bacteria to antibiotics or to decrease their number in the absence of an antibiotic (Asami 2002, Bai 2006, Caubet 2004).
By exploiting this idea between 2011 and 2015, in the framework of the APELBIO project resulting from the ECO-INDUSTRY program of the French Ministry of Industry and carried out by the SME LEAS, in collaboration with SCHNEIDER ELECTRIC and two Grenoble laboratories involved in this project (IMEP-LAHC and IGE), we validated an innovative, non-polluting and energy-saving experimental concept for the prevention of microbial contamination in aqueous media . We noted that the optimal frequency for which this inhibition was maximal appeared to depend on the type of bacterium, which was confirmed by our numerical simulations using the COMSOL Multiphysics software with an original model (Xavier 2017). So we had the idea of using a white noise source (10kHz-10MHz) instead of a CW source. Our results, better than with a fixed frequency source, are in the state of the art and led to a patent in May 2015. Unfortunately, the fine mechanisms leading to the growth inhibition of bacterial cells could not be precisely identified. This is what we intend to begin to do in the framework of this master thesis project.

1 / Design and realization of a compact instrument covering the 10 Hz – 50 MHz range for pilot experiments. This stand-alone instrument is based on the implementation of a DDS component in conjunction with a microcontroller. It will have the task of generating in a perfectly controlled manner the electromagnetic noise enabling the decontamination and, alternatively, of measuring the impedance detecting the decontaminating effect. A first prototype has already been developed recently and allowed us to carry out preliminary tests with the bacterium Escherichia coli.
The in situ detection of the decontamination efficiency requires a bio-impedance measurement of the solution containing the microorganisms. This last subject has, for many years, given rise to many patents and works: we know what toavoid to build a compact device, insensitive to the effects of electrodes

2 / First decontamination tests carried out following a wide range of physical conditions (amplitude and frequency of electromagnetic waves), chemical (variable geochemical environment, in terms of composition and strength ionic properties of the solution, which have an important effect on the surface properties of living cells, such as their zeta potential or their dispersed or agglomerated state which can potentially modulate electromagnetic effects) and biological (the type of bacterium studied could influence the electromagnetic effects already Observed on E. coli).


* IMEP-LAHC and IGE groups
Xavier P., D. Rauly, E. Chamberod and J.M.F. Martins. Theoretical evidence of maximum intracellular currents vs frequency in an Escherichia coli cell submitted to AC voltage. Bioelectromagnet. J. DOI:10.1002/bem.22033.
Archundia D., C. Duwig, L. Spadini, G. Uzu, S. Guédron, M.C. Morel, R. Cortez, Oswaldo Ramos, J. Chincheros, and J.M.F. Martins. How uncontrolled urban expansion increases the contamination of the Titicaca lake basin (El Alto – La Paz, Bolivia). Water, Air and Soil Pollution J. In press. 2017.
Navel A., L. Spadini, J.M.F. Martins, E. Vince and I. Lamy. Soil aggregates as a scale to investigate organic matter versus clay reactivities toward metals and protons. Accepted with revision. Eur. J. Soil Sci. 2017.
Archundia, D., C. Duwig, F. Lehembre, S. Chiron, M-C Morel, B. Prado, M. Bourdat-Deschamps, E. Vince, G. Flores Aviles and J.M.F. Martins. Antibiotic pollution in the Katari subcatchment of the Titicaca Lake: major transformation products and occurrence of resistance genes. Sci. Total Environ. 576 : (15) 671–682. 2017.
Ivankovic T., S. Rolland du Roscoat, C. Geindreau, P. Séchet, Z. Huang and J.M.F. Martins. Development and evaluation of an experimental and protocol for 3D visualization and characterization of bacterial biofilm’s structure in porous media using laboratory X-Ray Tomography. (GBIF-2016-0154). In press Biofouling J.
Simonin M., J.M.F. Martins, G. Uzu, E. Vince and A. Richaume. A combined study of TiO2 nano-particles transport and toxicity on microbial communities under acute and chronic exposures in soil columns. DOI: 10.1021/acs.est.6b02415. Environ. Sci. & Technol. 50: 10693–10699. 2016.
Simonin M., J. P. Guyonnet, J.M.F. Martins, M. Ginot and A. Richaume. Influence of soil properties on the toxicity of TiO2 nanoparticles on carbon mineralization and bacterial abundance. J. Haz. Mat. 283: 529-535. 2015.
D. Rauly, E. Chamberod, P. Xavier, J. M.F. Martins, J. Angelidis, H. Belbachir. First approach toward a modelling of the impedance spectroscopic behavior of microbial living cells, COMSOL Conference, Grenoble, 14-16 Octobre 2015
D. Rauly, E. Chamberod, P. Xavier, J. M.F. Martins, J. Angelidis, H. Belbachir, Stochastic Approach for EM Modelling of Suspended Bacterial Cells with Non-Uniform Geometry & Orientation Distribution, 36ème Progress In Electromagnetics Research Symposium (PIERS 2015), Prague (Rép Tchèque), 06-09/07/2015

* Others
Asami K. 2002. Characterization of biological cells by dielectric spectroscopy. Journal of Non-Crystalline Solids 305(1–3):268–277.
Blenkinsopp, A E Khoury, and J W Costerton. Electrical Enhancement of biocide efficay against Pseudomonas aeruginosa biofilms. Applied and Environmental Microbiology    Appl. Environ. Microbiol. November 1992 ; 58:11 3770-3773
Bai W, Zhao KZ, Asami K. 2006. Dielectric properties of E. coli cell as simulated by the three-shell spheroidal model. Biophysical Chemistry 122 :136–142.
Caubet R, Pedarros-Caubet F, Chu M, Freye E, de Belém Rodrigues M, Moreau JM, Ellison WJ. 2004. A radio frequency electric current enhances antibiotic efficacy against bacterial biofilms. Antimicrobial Agents and Chemotherapy 48(12):4662-4664.
Costerton JW, Ellis B, Lam K, Johnson F, Khoury AE. 1994. Mechanism of electrical enhancement of efficacy of antibiotics in killing biofilm bacteria. Antimicrobial Agents and Chemotherapy 38(12):2803-2809.
Giladi M, Porat Y, Blatt A, Wasserman Y, Kirson ED, Dekel E, Palti Y. 2008. Microbial growth inhibition by alternating electric fields. Antimicrobial Agents Chemotherapy 52(10):3517–3522.
Guiné V, Spadini L, Muris M., Sarret G., Delolme C., Gaudet JP, Martins JMF. 2006, Zinc Sorption to cell wall components of three gram-negative bacteria: a combined titration. Modelling and EXAFS study. Environ. Sci. Technol.  40 :1806-1813.

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