Effects of a static magnetic field on cell growth and gene expression in Escherichia coli

Electromagnetic fields effects on microbial growth in cocoa fermentation: A controlled experimental approach using established growth models

Understanding the effects of electromagnetic fields is crucial in the fermentation of cocoa beans, since through precise control of fermentation conditions the sensory and nutritional properties of cocoa beans could be improved. This study aimed to evaluate the effect of oscillating magnetic fields (OMF) on the kinetic growth of the core microbial communities of the Collections Castro Naranjal (CCN 51) cocoa bean. The data was obtained by three different models: Gompertz, Baranyi, and Logistic. The cocoa beans were subjected to different OMF strengths ranging from 0 mT to 80 mT for 1 h using the Helmholtz coil electromagnetic device. The viable microbial populations of lactic acid bacteria (LAB), acetic acid bacteria (AAB), and yeast (Y) were quantified using the colony-forming unit (CFU) counting method. The logistic model appropriately described the growth of LAB and Y under magnetic field exposure. Whereas the Baranyi model was suitable for describing AAB growth. The microbial populations in cocoa beans exposed to magnetic fields showed lower (maximum specific growth rate (μmax), values than untreated controls, with AAB exhibiting the highest average growth rate value at 5 mT and Y having the lowest average maximum growth rate value at 80 mT. The lower maximum specific growth rates and longer lag phases when exposed to magnetic fields compared to controls demonstrate the influence of magnetic fields on microbial growth kinetics.

Improving microbial production of value-added products through the intervention of magnetic fields

The magnetic field application is emerging as an auxiliary physical strategy to facilitate rapid biomass accumulation and intracellular production of compounds. However, the underlying mechanisms and principles governing the application of magnetic fields for microbial growth and biotransformation are not yet fully understood. Therefore, a better understanding of interdisciplinary technologies integration, expanded magnetic field application, and scaled-up industrial implementation is crucial. In this review, the magnetic field characteristics, magnetic field-assisted fermentation devices, and the working mechanism of magnetic field have been reviewed comprehensively from both physical and microbiological perspectives. The review suggests that magnetic fields affect the biochemical processes in microorganisms by mediating nutrient transport across membranes, electron transfer during photosynthesis and respiration, enzyme activity and gene expression. Moreover, the recent advances in magnetic field application for microbial fermentation and conversion in biochemical, food and agricultural fields have been summarized.

The use of the electromagnetic field in microbial process bioengineering

An electromagnetic field (EMF) has been shown to have various stimulatory or inhibitory effects on microorganisms. Over the years, growing interest in this topic led to numerous discoveries suggesting the potential applicability of EMF in biotechnological processes. Among these observations are stimulative effects of this physical influence resulting in intensified biomass production, modification of metabolic activity, or pigments secretion. In this review, we present the current state of the art and underline the main findings of the application of EMF in bioprocessing and their practical meaning in process engineering using examples selected from studies on bacteria, archaea, microscopic fungi and yeasts, viruses, and microalgae. All biological data are presented concerning the classification of EMF. Furthermore, we aimed to highlight missing parts of contemporary knowledge and indicate weak spots in the approaches found in the literature.

Effects of non-ionizing electromagnetic fields on flora and fauna, Part 2 impacts: how species interact with natural and man-made EMF

Ambient levels of nonionizing electromagnetic fields (EMF) have risen sharply in the last five decades to become a ubiquitous, continuous, biologically active environmental pollutant, even in rural and remote areas. Many species of flora and fauna, because of unique physiologies and habitats, are sensitive to exogenous EMF in ways that surpass human reactivity. This can lead to complex endogenous reactions that are highly variable, largely unseen, and a possible contributing factor in species extinctions, sometimes localized. Non-human magnetoreception mechanisms are explored. Numerous studies across all frequencies and taxa indicate that current low-level anthropogenic EMF can have myriad adverse and synergistic effects, including on orientation and migration, food finding, reproduction, mating, nest and den building, territorial maintenance and defense, and on vitality, longevity and survivorship itself. Effects have been observed in mammals such as bats, cervids, cetaceans, and pinnipeds among others, and on birds, insects, amphibians, reptiles, microbes and many species of flora. Cyto- and geno-toxic effects have long been observed in laboratory research on animal models that can be extrapolated to wildlife. Unusual multi-system mechanisms can come into play with non-human species - including in aquatic environments - that rely on the Earth's natural geomagnetic fields for critical life-sustaining information. Part 2 of this 3-part series includes four online supplement tables of effects seen in animals from both ELF and RFR at vanishingly low intensities. Taken as a whole, this indicates enough information to raise concerns about ambient exposures to nonionizing radiation at ecosystem levels. Wildlife loss is often unseen and undocumented until tipping points are reached. It is time to recognize ambient EMF as a novel form of pollution and develop rules at regulatory agencies that designate air as 'habitat' so EMF can be regulated like other pollutants. Long-term chronic low-level EMF exposure standards, which do not now exist, should be set accordingly for wildlife, and environmental laws should be strictly enforced - a subject explored in Part 3.

Molecular Evaluation of the Impact of Nd:YAG Laser and Static Magnetic Field on Genomic DNA of Some Bacterial Isolates using RAPD-PCR

Antimicrobial therapy is frequently associated with the emergence of resistant bacteria with a high rate of morbidity and mortality worldwide. The present study was aimed at investigating the impact of a neodymium-doped yttrium aluminum (Nd:YAG) laser, and a static magnetic field (SMF) on cellular growth and DNA alteration in some clinical bacterial isolates. Samples from cutaneous wounds were collected by sterile cotton swabs from three elderly women admitted to Tikrit Teaching Hospital, Tikrit City, Iraq. Isolation and identification of Streptococcus agalactiae, Staphylococcus aureus, and Pseudomonas aeruginosa were carried out using cultural characteristics, microscopy, and biochemical tests. Three broth cultures were prepared for each of the test isolates. The first broth culture served as untreated control, the second was exposed to an Nd:YAG laser and the third was exposed to SMF. Colony counting was done on all the samples. DNA was extracted from the test bacteria and used to perform the RAPD-PCR assay. In contrast to the untreated control, the results showed that Nd:YAG laser radiation was more effective than SMF at inhibiting the cellular growth of the test isolates. Also, the radiation caused DNA alteration, which was established by decreased microbial growth, as well as the development of new bands and the loss of original bands. According to the findings of this study, the Nd:YAG laser is a promising technique for influencing the healing of infected cutaneous wounds. RAPD-PCR is also a useful biomarker assay for assessing the biological impact of laser radiation and SMF on bacteria.

Regulatory and Enterotoxin Gene Expression and Enterotoxins Production in Staphylococcus aureus FRI913 Cultures Exposed to a Rotating Magnetic Field and trans-Anethole

The study aimed to examine the influence of a rotating magnetic field (RMF) of two different frequencies (5 and 50 Hz) on the expression of regulatory (agrA, hld, rot) and staphylococcal enterotoxin (SE—sea, sec, sel) genes as well as the production of SEs (SEA, SEC, SEL) by the Staphylococcus aureus FRI913 strain cultured on a medium supplemented with a subinhibitory concentration of trans-anethole (TA). Furthermore, a theoretical model of interactions between the bacterial medium and bacterial cells exposed to RMF was proposed. Gene expression and SEs production were measured using quantitative real-time PCR and ELISA techniques, respectively. Based on the obtained results, it was found that there were no significant differences in the expression of regulatory and SE genes in bacteria simultaneously cultured on a medium supplemented with TA and exposed to RMF at the same time in comparison to the control (unexposed to TA and RMF). In contrast, when the bacteria were cultured on a medium supplemented with TA but were not exposed to RMF or when they were exposed to RMF of 50 Hz (but not to TA), a significant increase in agrA and sea transcripts as compared to the unexposed control was found. Moreover, the decreased level of sec transcripts in bacteria cultured without TA but exposed to RMF of 50 Hz was also revealed. In turn, a significant increase in SEA and decrease in SEC and SEL production was observed in bacteria cultured on a medium supplemented with TA and simultaneously exposed to RMFs. It can be concluded, that depending on SE and regulatory genes expression as well as production of SEs, the effect exerted by the RMF and TA may be positive (i.e., manifests as the increase in SEs and/or regulatory gene expression of SEs production) or negative (i.e., manifests as the reduction in both aforementioned features) or none.

Effects of non-ionizing electromagnetic fields on flora and fauna, part 1. Rising ambient EMF levels in the environment

Ambient levels of electromagnetic fields (EMF) have risen sharply in the last 80 years, creating a novel energetic exposure that previously did not exist. Most recent decades have seen exponential increases in nearly all environments, including rural/remote areas and lower atmospheric regions. Because of unique physiologies, some species of flora and fauna are sensitive to exogenous EMF in ways that may surpass human reactivity. There is limited, but comprehensive, baseline data in the U.S. from the 1980s against which to compare significant new surveys from different countries. This now provides broader and more precise data on potential transient and chronic exposures to wildlife and habitats. Biological effects have been seen broadly across all taxa and frequencies at vanishingly low intensities comparable to today's ambient exposures. Broad wildlife effects have been seen on orientation and migration, food finding, reproduction, mating, nest and den building, territorial maintenance and defense, and longevity and survivorship. Cyto- and geno-toxic effects have been observed. The above issues are explored in three consecutive parts: Part 1 questions today's ambient EMF capabilities to adversely affect wildlife, with more urgency regarding 5G technologies. Part 2 explores natural and man-made fields, animal magnetoreception mechanisms, and pertinent studies to all wildlife kingdoms. Part 3 examines current exposure standards, applicable laws, and future directions. It is time to recognize ambient EMF as a novel form of pollution and develop rules at regulatory agencies that designate air as 'habitat' so EMF can be regulated like other pollutants. Wildlife loss is often unseen and undocumented until tipping points are reached. Long-term chronic low-level EMF exposure standards, which do not now exist, should be set accordingly for wildlife, and environmental laws should be strictly enforced.

Static Magnetic Field Inhibits Growth of Escherichia coli Colonies via Restriction of Carbon Source Utilization

Magnetobiological effects on growth and virulence have been widely reported in Escherichia coli (E. coli). However, published results are quite varied and sometimes conflicting because the underlying mechanism remains unknown. Here, we reported that the application of 250 mT static magnetic field (SMF) significantly reduces the diameter of E. coli colony-forming units (CFUs) but has no impact on the number of CFUs. Transcriptomic analysis revealed that the inhibitory effect of SMF is attributed to differentially expressed genes (DEGs) primarily involved in carbon source utilization. Consistently, the addition of glycolate or glyoxylate to the culture media successfully restores the bacterial phenotype in SMF, and knockout mutants lacking glycolate oxidase are no longer sensitive to SMF. These results suggest that SMF treatment results in a decrease in glycolate oxidase activity. In addition, metabolomic assay showed that long-chain fatty acids (LCFA) accumulate while phosphatidylglycerol and middle-chain fatty acids decrease in the SMF-treated bacteria, suggesting that SMF inhibits LCFA degradation. Based on the published evidence together with ours derived from this study, we propose a model showing that free radicals generated by LCFA degradation are the primary target of SMF action, which triggers the bacterial oxidative stress response and ultimately leads to growth inhibition.

The Impact of Intraspecies Variability on Growth Rate and Cellular Metabolic Activity of Bacteria Exposed to Rotating Magnetic Field

Majority of research on the influence of magnetic fields on microorganisms has been carried out with the use of different species or different groups of microorganisms, but not with the use of different strains belonging to one species. The purpose of the present study was to assess the effect of rotating magnetic fields (RMF) of 5 and 50 Hz on the growth and cellular metabolic activity of eight species of bacteria: Staphylococcus aureus, Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella pneumoniae, Enterococcus faecalis, Enterobacter cloacae, Moraxella catarrhalis, and Bacillus cereus. However, contrary to the research conducted so far, each species was represented by at least four different strains. Moreover, an additional group of S. aureus belonging to a single clonal type but representing different biotypes was also included in the experiment. The results showed a varied influence of RMF on growth dynamics and cellular metabolic activity, diversified to the greatest extent in dependence on the bacterial strain exposed to the RMF and to a lesser extent in dependence on the frequency of the generated magnetic field. It was found that, with regard to the exposed strain of the same species, the effect exerted by the RMF may be positive (i.e., manifests as the increase in the growth rate or/and cellular metabolic activity) or negative (i.e., manifests as a reduction of both aforementioned features) or none. Even when one clonal type of S. aureus was used, the results of RMF exposure also varied (although the degree of differentiation was lower than for strains representing different clones). Therefore, the research has proven that, apart from the previously described factors related primarily to the physical parameters of the magnetic field, one of the key parameters affecting the final result of its influence is the bacterial intraspecies variability.

relA and spoT Gene Expression is Modulated in Salmonella Grown Under Static Magnetic Field

Virtually all bacterial species synthesize high levels of (p)ppGpp (guanosine penta- or tetraphosphate), a pleiotropic regulator of the stringent response and other stresses in bacteria. relA and spoT genes are, respectively, involved in synthesis and synthesis/biodegradation of (p)ppGpp. We aimed in this work to evaluate the impact of static magnetic field (SMF) 200 mT exposure on the expression of relA and spoT genes in Salmonella enterica Hadar. Bacteria were exposed to a SMF during 9 h, and RNA extraction was followed by reverse transcriptase polymerase chain reaction (RT-PCR). The relative quantification of mRNA expression levels using the 16S rRNA reference gene did not change during the SMF exposure. However, results showed a significant increase in gene expression for relA after 3 h of exposure (P < 0.05) and after 6 h for spoT (P < 0.05). The differential gene expression of relA and spoT could be considered as a potential stress response to a SMF exposure in Salmonella related to the production/degradation of (p)ppGpp.

The Effect of Static Magnetic Field on Methanogenesis in the Anaerobic Digestion of Municipal Sewage Sludge

The present study aimed to determine the effect of a 17.6 mT static magnetic field (SMF) on the efficiency of anaerobic digestion (AD) of municipal sewage sludge (MSS). The SMF had a significant impact on methane (CH4) production efficiency, the levels of fermentation rate (ηFMSS) vs. removal rate (ηVS), and the structure of the anaerobic bacteria consortium, but it did not affect cumulative biogas production. The highest CH4 yield (431 ± 22 dm3CH4/kgVS) and the highest methane content in the biogas (66.1% ± 1.9%) were found in the variant in which the SMF exposure time was 144 min/day. This variant also produced the highest ηFMSS and ηVS values, reaching 73.8% ± 2.3% and ηVS 36.9% ± 1.6%, respectively. Longer anaerobic sludge retention time in the SMF area significantly decreased AD efficiency and caused a significant reduction in the number of methanogens in the anaerobic bacteria community. The lowest values were observed for SMF exposure time of 432 min/day, which produced only 54.8 ± 1.9% CH4 in the biogas. A pronounced reduction was recorded in the Archaea (ARC915) and Methanosaeta (MX825) populations in the anaerobic sludge, i.e., to 20% ± 11% and 6% ± 2%, respectively.

Intrinsically Magnetic Cells: A Review on Their Natural Occurrence and Synthetic Generation

The magnetization of non-magnetic cells has great potential to aid various processes in medicine, but also in bioprocess engineering. Current approaches to magnetize cells with magnetic nanoparticles (MNPs) require cellular uptake or adsorption through in vitro manipulation of cells. A relatively new field of research is "magnetogenetics" which focuses on in vivo production and accumulation of magnetic material. Natural intrinsically magnetic cells (IMCs) produce intracellular, MNPs, and are called magnetotactic bacteria (MTB). In recent years, researchers have unraveled function and structure of numerous proteins from MTB. Furthermore, protein engineering studies on such MTB proteins and other potentially magnetic proteins, like ferritins, highlight that in vivo magnetization of non-magnetic hosts is a thriving field of research. This review summarizes current knowledge on recombinant IMC generation and highlights future steps that can be taken to succeed in transforming non-magnetic cells to IMCs.

Regulation of Electromagnetic Perceptive Gene Using Ferromagnetic Particles for the External Control of Calcium Ion Transport

Developing synthetic biological devices to allow the noninvasive control of cell fate and function, in vivo can potentially revolutionize the field of regenerative medicine. To address this unmet need, we designed an artificial biological “switch” that consists of two parts: (1) the electromagnetic perceptive gene (EPG) and (2) magnetic particles. Our group has recently cloned the EPG from the Kryptopterus bicirrhis (glass catfish). The EPG gene encodes a putative membrane-associated protein that responds to electromagnetic fields (EMFs). This gene’s primary mechanism of action is to raise the intracellular calcium levels or change in flux through EMF stimulation. Here, we developed a system for the remote regulation of [Ca²⁺]_i (i.e., intracellular calcium ion concentration) using streptavidin-coated ferromagnetic particles (FMPs) under a magnetic field. The results demonstrated that the EPG-FMPs can be used as a molecular calcium switch to express target proteins. This technology has the potential for controlled gene expression, drug delivery, and drug developments.

Effect of static magnetic field on morphology and growth metabolism of Flavobacterium sp. m1-14

Increasing evidence shows that static magnetic fields (SMFs) can affect microbial growth metabolism, but the specific mechanism is still unclear. In this study, we have investigated the effect of moderate-strength SMFs on growth and vitamin K₂ biosynthesis of Flavobacterium sp. m1-14. First, we designed a series of different moderate-strength magnetic field intensities (0, 50, 100, 150, 190 mT) and exposure times (0, 24, 48, 72, 120 h). With the optimization of static magnetic field intensity and exposure time, biomass and vitamin K₂ production significantly increased compared to control. The maximum vitamin K₂ concentration and biomass were achieved when exposed to 100 mT SMF for 48 h; compared with the control group, they increased by 71.3% and 86.8%, respectively. Interestingly, it was found that both the cell viability and morphology changed significantly after SMF treatment. Second, the adenosine triphosphate (ATP) and glucose-6-phosphate dehydrogenase (G6PDH) metabolism is more vigorous after exposed to 100 mT SMF. This change affects the cell energy metabolism and fermentation behavior, and may partially explain the changes in bacterial biomass and vitamin K₂ production. The results show that moderate-strength SMFs may be a promising method to promote bacterial growth and secondary metabolite synthesis.

Enhancement of mixture pollutant biodegradation efficiency using a bacterial consortium under static magnetic field

One of the main challenges of bioremediation is to define efficient protocols with low environmental impact and high removal rates, such as static magnetic field (SMF). The aim of this study was to evaluate the effect of SMF exposure on the biodegradation rate of a mixture of pollutants using three bacterial strains which were isolated and identified from the Bizerte lagoon: Pseudomonas stutzeri LBR (KC157911), Cupriavidus metallidurans LBJ (KU659610) and Rhodococcus equi LBB (KU743870). To recognize the improvement role of SMF, the culture was submitted to a pre-treatment with SMF with an induction equal to 200 mT for 5 hours, after that the degradation experiment was followed with individual strains and with a consortium. Results showed an increase by 20% in the growth of the exposed bacterial population compared to controls, and 98% of biodegradation of DDT and 90% for BaP after 30 days of follow-up. This encouraging data opens new perspectives for a bioremediation bioprocess using SMF.

The Effects of Weak Static Magnetic Field on the Development of Organotypic Tissue Culture in Rats

The effects of weak static magnetic field on the organotypic tissue culture of the rat cerebral cortex, liver, and spleen have been investigated. Exposure to a 200 μT static magnetic field induces tissue development, leading to the intensification of regeneration processes compared to the control explants.

Impact of a static magnetic field on biodegradation of wastewater compounds and bacteria recombination

The current study presents results concerning the effect of a static magnetic field (SMF) on synthetic wastewater biodegradation by activated sludge and on dehydrogenase activity of microorganisms of activated sludge. The highest process efficiency was obtained for a SMF of 0.0075 T among the tested magnetic flux density values of 0.005-0.14 T. Decrease in COD was 25% higher for the bioreactor exposed to SMF compared with control experiments. The positive effect of SMF 0.0075-0.0080 T was confirmed in experiments on the dehydrogenase activity of activated sludge. It was also shown that a SMF of 0.007 T increased p-nitroaniline removal from wastewater and influenced the recombination frequency in a streptomycin-resistant bacteria strain of Eschercihia coli.

Viability and membrane lipid composition under a 57mT static magnetic field in Salmonella Hadar

The aim of this work is to demonstrate the effects of a static magnetic field (SMF) with an induction 12 equal to 57mT on the viability and membrane lipid composition of Salmonella Hadar. Results showed an increase in the viability of exposed bacteria compared to controls after 9h of exposure. Analysis with gas chromatography of total lipids (TLs) and different fractions of phospholipids: phosphatidylglycerols (PGs), phosphatidylethanolamines (PEs), and cardiolipins (CLs), separated by thin layer chromatography revealed changes in fatty acid levels during exposure. For TLs, the unsaturated fatty acids/saturated fatty acids ratio (UFAs/SFAs) had significantly increased after 9 h of exposure. The variation of this ratio seems to be essentially due to the increase of the proportion of unsaturated fatty acids with 18 carbons, in particular C_18:1. The analyses of fatty acid composition carried out on the scale of each fraction of phospholipids showed that CLs contributed significantly to the increase of the proportion of the unsaturated fatty acids between 6 and 9h of exposure thanks to their unsaturated chains with 18 carbons (especially C_18:2). CLs appear to be the main phospholipid involved in the adaptation of S. Hadar membranes to the SMF.

Effects of prolonged exposure to moderate static magnetic field and its synergistic effects with alkaline pH on Enterococcus faecalis

Static magnetic field (SMF) has been shown to biologically affect various microorganisms, but its effects on Enterococcus faecalis, which is associated with multiple dental infections, have not been reported yet. Besides, Enterococcus faecalis was found to be resistant to the alkaline environment provided by a major dental antimicrobial, calcium hydroxide. Therefore, the antibacterial activity of prolonged exposure to moderate SMF (170 mT) and its possible synergistic activity with alkaline pH (pH = 9) were evaluated in the study. The ability to form a biofilm under these conditions was examined by crystal violet assay. Real-time quantitative PCR was performed to evaluate the relative expression of stress (dnaK and groEL) and virulence (efaA, ace, gelE and fsrC) related genes. As the results indicated, cell proliferation was inhibited after 120 h of SMF exposure. What's more, the combined treatment of SMF and alkaline pH showed significantly improved antimicrobial action when compared to single SMF and alkaline pH treatment for more than 24 h and 72 h respectively. However, the ability to form a biofilm was also enhanced under SMF and alkaline pH treatments. SMF can induce stress response by up-regulating the expression of dnaK and elevate virulence gene expression (efaA and ace). These responses were more significant and more genes were up-regulated including groEL, gelE and fsrC when exposed to SMF and alkaline pH simultaneously. Hence, combination of SMF and alkaline pH could be a promising disinfection strategy in dental area and other areas associated with Enterococcus faecalis infections.

Application of static and impulse magnetic fields to bacteria Rhodospirillum rubrum VKM B-1621

The paper presents effects of different magnetic fields (MFs) (static—SMF and impulse—IMF) on bacteria Rhodospirillum rubrum VKM B-1621. The MFs had different magnetic strength: SMF—up to 173 mT; IMF—25 mT. The studied object was amylase activity which was measured by decrease in the starch concentration during incubation in the MFs. The term of incubation in the MFs was limited with 2 h. The SMF affected neither amylase activity of R. rubrum nor standard deviation in distribution of the residual starch concentration along the plate but the IMF did. The IMS effects varied along the plate which could be related with distance from the magnetic center of the applied device. In whole, application of impulse MFs can regulate bacterial activity and thus could be used for biotechnological application.

Unraveling the expression of genes involved in the biosynthesis pathway of cardiolipin and phosphatidylethanolamine in Salmonella Hadar grown under static magnetic field 200 mT

We aimed in this work to evaluate the effect of static magnetic field 200 mT (SMF) on the expression of genes involved in the biosynthetic pathway of cardiolipin: g3pd, plsB, cdsA, pgsA, pgpA, cls and phosphatidylethanolamine: pssA and psd in Salmonella enterica subsp enterica serovar Hadar. Bacteria were exposed to a SMF during 3, 6 and 9 h. RNA extraction was followed by Reverse Transcriptase Polymerase Chain Reaction RT-PCR. The relative quantification of mRNA expression levels using 16S rRNA doesn't change during the time exposure. RT-PCR was done for two exposure experiments. The gene expression using RT-PCR present no significant difference in case of plsB, cdsA, pgpA, pgsA and psd genes during the different exposure times. However, a significant increase was observed in the expression of g3pd and pssA genes after 6 h and for cls gene after 3 h of exposure, but any variation was notified after 9 h of exposure. So we can conclude from this study that cls, g3pd and pssA genes are required in the adaptation of Salmonella Hadar to SMF.

Effects of static magnetic fields on the enteropathogenic Escherichia coli

This study reports the effects of exposing cells of the prototypical enteropathogenic Escherichia coli (EPEC) strain E2348/69 to static magnetic fields (SMF) of varying intensities to observe their capacity to autoaggregate and the effect on cell adherence. The results showed that bacteria exposure over the course of 5 min to an intensity of 53 mT reduced autoaggregation by 28%. However, with intensities of up to 100 mT with the same exposure time, bacteria autoaggregation was reduced by approximately 50%; and after 30 min at the same intensity, it was indistinguishable from that observed in a non-autoaggregative strain. Furthermore, it was observed that SMF treatment also modified the typical localized adherence pattern of EPEC E2348/69. The observed effects are not related to bacteria damage. The above was confirmed because, after a 107 mT SMF treatment over the course of 30 min, cell viability and membrane permeability were the same to that observed in untreated controls. The obtained results suggest that the SMF effect on the E2348/69 EPEC strain alters the expression of the bundle-forming pilus (BFP), due to the fact that the same strain without the EPEC adherence factor plasmid that encodes the BFP operon was unable to autoaggregate. Electron microscopic analyses revealed structural differences between cells exposed to SMF with respect to untreated controls. In conclusion, the SMF treatment of 107 mT for 30 min reduced EPEC E2348/69 autoaggregation and modified its adherence pattern, with both events likely being associated with changes in BFP expression. Bioelectromagnetics. 38:570-578, 2017. © 2017 Wiley Periodicals, Inc.

Enhancing effect of 50 Hz rotating magnetic field on induction of Shiga toxin-converting lambdoid prophages

Studies aimed at investigating factors and mechanism of induction of prophages, a major pathogenesis factor of Shiga toxin-producing Escherichia coli (STEC), are considered important to develop an effective treatment for STEC infections. In this study, we demonstrated the synergistic effect of the rotating magnetic field (RMF) of induction B = 34 mT and frequency ƒ = 50 Hz at a constant temperature of 37 °C and mitomycin C (MMC), that resulted in a higher level of induction of stx-carrying lambdoid Stx prophages. This is a first report on the induction of lambdoid Stx prophages in response to the enhancing effect of popular inductor (mitomycin C) under the influence of RMF.

Effect of static magnetic field on endospore germination

This work investigated the effect of static magnetic field (SMF) on Bacillus atrophaeus endospore germination. Germination was triggered by L-alanine in 1.3-T SMF and characterized by ion release, Ca²⁺ -dipicolinic acid release, and water influx. These events were monitored by electrical conductivity, Tb-DPA fluorescence, and optical density, respectively. Culturability of endospore germinated in SMF exposure was evaluated by CFU enumeration. Results indicated that 1.3-T SMF failed to significantly affect endospore germination and culturability, suggesting that the three aforementioned processes were not sensitive to SMF. Bioelectromagnetics. 38:121-127, 2017. © 2016 Wiley Periodicals, Inc.

Effect of a static magnetic field on Escherichia coli adhesion and orientation

This preliminary study focused on the effect of exposure to 0.5 T static magnetic fields on Escherichia coli adhesion and orientation. We investigated the difference in bacterial adhesion on the surface of glass and indium tin oxide-coated glass when exposed to a magnetic field either perpendicular or parallel to the adhesion surface (vectors of magnetic induction are perpendicular or parallel to the adhesion surface, respectively). Control cultures were simultaneously grown under identical conditions but without exposure to the magnetic field. We observed a decrease in cell adhesion after exposure to the magnetic field. Orientation of bacteria cells was affected after exposure to a parallel magnetic field. On the other hand, no effect on the orientation of bacteria cells was observed after exposure to a perpendicular magnetic field.

Application of Higuchi's fractal dimension from basic to clinical neurophysiology: A review

BACKGROUND AND OBJECTIVE

For more than 20 years, Higuchi's fractal dimension (HFD), as a nonlinear method, has occupied an important place in the analysis of biological signals. The use of HFD has evolved from EEG and single neuron activity analysis to the most recent application in automated assessments of different clinical conditions. Our objective is to provide an updated review of the HFD method applied in basic and clinical neurophysiological research.

METHODS

This article summarizes and critically reviews a broad literature and major findings concerning the applications of HFD for measuring the complexity of neuronal activity during different neurophysiological conditions. The source of information used in this review comes from the PubMed, Scopus, Google Scholar and IEEE Xplore Digital Library databases.

RESULTS

The review process substantiated the significance, advantages and shortcomings of HFD application within all key areas of basic and clinical neurophysiology. Therefore, the paper discusses HFD application alone, combined with other linear or nonlinear measures, or as a part of automated methods for analyzing neurophysiological signals.

CONCLUSIONS

The speed, accuracy and cost of applying the HFD method for research and medical diagnosis make it stand out from the widely used linear methods. However, only a combination of HFD with other nonlinear methods ensures reliable and accurate analysis of a wide range of neurophysiological signals.

Engineered biomaterial and biophysical stimulation as combinatorial strategies to address prosthetic infection by pathogenic bacteria

A plethora of antimicrobial strategies are being developed to address prosthetic infection. The currently available methods for implant infection treatment include the use of antibiotics and revision surgery. Among the bacterial strains, Staphylococcus species pose significant challenges particularly, with regard to hospital acquired infections. In order to combat such life threatening infectious diseases, researchers have developed implantable biomaterials incorporating nanoparticles, antimicrobial reinforcements, surface coatings, slippery/non-adhesive and contact killing surfaces. This review discusses a few of the biomaterial and biophysical antimicrobial strategies, which are in the developmental stage and actively being pursued by several research groups. The clinical efficacy of biophysical stimulation methods such as ultrasound, electric and magnetic field treatments against prosthetic infection depends critically on the stimulation protocol and parameters of the treatment modality. A common thread among the three biophysical stimulation methods is the mechanism of bactericidal action, which is centered on biophysical rupture of bacterial membranes, the generation of reactive oxygen species (ROS) and bacterial membrane depolarization evoked by the interference of essential ion-transport. Although the extent of antimicrobial effect, normally achieved through biophysical stimulation protocol is insufficient to warrant therapeutic application, a combination of antibiotic/ROS inducing agents and biophysical stimulation methods can elicit a clinically relevant reduction in viable bacterial numbers. In this review, we present a detailed account of both the biomaterial and biophysical approaches for achieving maximum bacterial inactivation. Summarizing, the biophysical stimulation methods in a combinatorial manner with material based strategies can be a more potent solution to control bacterial infections. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2174-2190, 2017.

A magnetic-dependent protein corona of tailor-made superparamagnetic iron oxides alters their biological behaviors

In recent years, it is becoming increasingly evident that once nanoparticles come into contact with biological fluids, a protein corona surely forms and critically affects the biological behaviors of nanoparticles. Herein, we investigate whether the formation of protein corona on the surface of superparamagnetic iron oxides (SPIOs) is influenced by static magnetic field. Under static magnetic field, there is no obvious variation in the total amount of protein adsorption, but the proportion of adsorbed proteins significantly changes. Noticeably, certain proteins including apolipoproteins, complement system proteins and acute phase proteins, increase in the protein corona of SPIOs in the magnetic field. More importantly, the magnetic-dependent protein corona of SPIOs enhances the cellular uptake of SPIOs into the normal cell line (3T3 cells) and tumor cell line (HepG2 cells), due to increased adsorption of apolipoprotein. In addition, SPIOs with the magnetic-dependent protein corona cause high cytotoxicity to 3T3 cells and HepG2 cells. This work discloses that superparamagnetism as a key feature of SPIOs affects the composition of protein corona to a large extent, which further alters the biological behaviors of SPIOs.

Strategies to enhance the production of photosynthetic pigments and lipids in chlorophycae species

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Microalgae are source of valuable compounds as lipids, proteins, carbohydrates, pigments among others.

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Culture stress conditions increase biomass and high values compounds in microalgae.

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Nitrogen and salt stress increase lipids in microalgae.

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Two stages culture and electromagnetic fields enhancing microalgae biomass and pigments content.

Microalgae are a major natural source for a vast array of valuable compounds as lipids, proteins, carbohydrates, pigments among others. Despite many applications, only a few species of microalgae are cultured commercially because of poorly developed of cultivation process. Nowadays some strategies of culture have been used for enhancing biomass and value compounds yield. The most strategies applied to microalgae are classified into two groups: nutrimental and physical. The nutrimental are considered as change in media composition as nitrogen and phosphorous limitation and changes in carbon source, while physical are described as manipulation in operational conditions and external factors such as application of high-light intensities, medium salinity and electromagnetic fields. The exposition to electromagnetic field is a promising technique that can improve the pigments and biomass yield in microalgae culture. Therefore, is important to describe the advantages and applications of the overall process. The aim of this review was to describe the main culture strategies used to improve the photosynthetic and lipids content in chlorophyceae species.

Effect of GO-Fe3O4 and rotating magnetic field on cellular metabolic activity of mammalian cells

The effect of hybrid material-graphene flakes with Fe3O4 nanospheres (GO-Fe3O4), graphene oxide (GO) and magnetite nanospheres (Fe3O4) in rotating magnetic field on mammalian cells metabolism has been studied. Several reports shown that exposure to magnetic field may have influence on cellular membrane permeability. Thus, the aim of presented study was to determine the cellular response of L929 fibroblast cells to nanomaterials and rotating magnetic field for 8-h exposure experiment. The GO had tendency to adsorb proteins, thus cell metabolism was decreased and the effect of that mechanism was enhanced by impact of nanospheres and rotating magnetic field. The highest reduction of cellular metabolism was recorded for WST-1 and NR assays at concentration 100 µg/mL of all tested nanomaterials and magnetic induction value 10.06 mT. The lactate dehydrogenase leakage assay has shown significant changes in membrane permeability. Further studies need to be carried out to precisely determine the mechanism of that process.

Influence of the magnetic field on microorganisms in the oral cavity

Since the beginning of their lives, all living organisms are exposed to the influence of geomagnetic fields.

Magnetic fields suppress Pseudomonas aeruginosa biofilms and enhance ciprofloxacin activity

Due to the refractory nature of pathogenic microbial biofilms, innovative biofilm eradication strategies are constantly being sought. Thus, this study addresses a novel approach to eradicate Pseudomonas aeruginosa biofilms. Magnetic nanoparticles (MNP), ciprofloxacin (Cipro), and magnetic fields were systematically evaluated in vitro for their relative anti-biofilm contributions. Twenty-four-hour biofilms exposed to aerosolized MNPs, Cipro, or a combination of both, were assessed in the presence or absence of magnetic fields (Static one-sided, Static switched, Oscillating, Static + oscillating) using changes in bacterial metabolism, biofilm biomass, and biofilm imaging. The biofilms exposed to magnetic fields alone exhibited significant metabolic and biomass reductions (p < 0.05). When biofilms were treated with a MNP/Cipro combination, the most significant metabolic and biomass reductions were observed when exposed to static switched magnetic fields (p < 0.05). The exposure of P. aeruginosa biofilms to a static switched magnetic field alone, or co-administration with MNP/Cipro/MNP + Cipro appears to be a promising approach to eradicate biofilms of this bacterium.

Exposure to extremely low-frequency magnetic field affects biofilm formation by cystic fibrosis pathogens

SUMMARY 

Aims: To evaluate the in vitro effects of extremely low-frequency magnetic field (ELF-MF) on growth and biofilm formation by Staphylococcus aureus, Pseudomonas aeruginosa, Burkholderia cepacia and Stenotrophomonas maltophilia strains from cystic fibrosis patients. Materials & methods: The motion of selected ions (Fe, Ca, Cu, Zn, Mg, K, Na) was stimulated by the ion resonance effect, then influence on growth and biofilm formation/viability was assessed by spectrophotometry or viability count. Results: Generally, exposure to ELF-MF significantly increased bacterial growth and affected both biofilm formation and viability, although with differences with regard to ions and species considered. Conclusion: Exposure to ELF-MF represents a possible new approach for treatment of biofilm-associated cystic fibrosis lung infections.

Electromagnetic fields as structure-function zeitgebers in biological systems: environmental orchestrations of morphogenesis and consciousness

Within a cell system structure dictates function. Any interaction between cells, or a cell and its environment, has the potential to have long term implications on the function of a given cell and emerging cell aggregates. The structure and function of cells are continuously subjected to modification by electrical and chemical stimuli. However, biological systems are also subjected to an ever-present influence: the electromagnetic (EM) environment. Biological systems have the potential to be influenced by subtle energies which are exchanged at atomic and subatomic scales as EM phenomena. These energy exchanges have the potential to manifest at higher orders of discourse and affect the output (behavior) of a biological system. Here we describe theoretical and experimental evidence of EM influence on cells and the integration of whole systems. Even weak interactions between EM energies and biological systems display the potential to affect a developing system. We suggest the growing literature of EM effects on biological systems has significant implications to the cell and its functional aggregates.

Cell-host, LINE and environment: Three players in search of a balance

Long interspersed nuclear elements -1 (LINEs, L1s) are retroelements occupying almost 17% of the human genome. L1 retrotransposition can cause deleterious effects on the host-cell and it is generally inhibited by suppressive mechanisms, but it can occur in some specific cells during early development as well as in some tumor cells and in the presence of several environmental factors. In a recent publication we reported that extremely low frequency pulsed magnetic field can affect L1 retrotransposition in neuroblastoma cells. In this commentary we discuss the interaction between environment and L1 activity in the light of the new emerging paradigm of host-LINE relationship.

Neuroprotective effect of weak static magnetic fields in primary neuronal cultures

Low intensity static magnetic fields (SMFs) interact with various biological tissues including the CNS, thereby affecting key biological processes such as gene expression, cell proliferation and differentiation, as well as apoptosis. Previous studies describing the effect of SMFs on apoptotic cell death in several non-neuronal cell lines, emphasize the importance of such a potential modulation in the case of neurodegenerative disorders, where apoptosis constitutes a major route via which neurons degenerate and die. In this study, we examine the effect of SMFs on neuronal survival in primary cortical and hippocampal neurons that constitute a suitable experimental system for modeling the neurodegenerative state in vitro. We show that weak SMF exposure interferes with the apoptotic programing in rat primary cortical and hippocampal neurons, thereby providing protection against etoposide-induced apoptosis in a dose- and time-dependent manner. Primary cortical neurons exposed to SMF (50G) for 7days exhibited a 57.1±6.3% decrease in the percentage of cells undergoing apoptosis induced by etoposide (12μM), accompanied by a marked decrease in the expression of the pro-apoptotic markers: cleaved poly ADP ribose polymerase-1, cleaved caspase-3, active caspase-9 and the phospho-histone H2A variant (Ser139) by 41.0±5.0%, 81.2±5.0%, 72.9±6.4%, 42.75±2.9%, respectively, and by a 57.2±1.0% decrease in the extent of mitochondrial membrane potential collapse. Using the L-type voltage-gated Ca(2+) channel inhibitor nifedipine, which is selective to Ca(2+) influx through Cav1.2, we found that the anti-apoptotic effect of SMFs was mediated by Ca(2+) influx through these channels. Our findings demonstrating altered Ca(2+)-influx in response to thapsigargin stimulation in SMF-exposed cortical neurons, along with enhanced inhibition of KCl-induced Ca(2+)-influx through Cav1.2 channels and enhanced expression of Cav1.2 and Cav1.3 channels, allude to the involvement of voltage- and store-operated Ca(2+) channels in various aspects of the protective effect exerted by SMFs. These findings show the potential susceptibility of the CNS to weak SMF exposure and have implications for the design of novel strategies for the treatment and/or prevention of neurodegenerative diseases.

An in vitro study of the impact of 4mT static magnetic field to modify the differentiation rate of rat bone marrow stem cells into primordial germ cells

This investigation was performed to evaluate the differentiation capacity and alteration in genes expression patterns during in vitro differentiation of bone marrow stem cells into primordial germ cells using static magnetic field (4mT) and BMP-4 (25ng/ml). The rate of differentiation was investigated using the Real Time-PCR method for tracing expression of differentiation markers (Oct-4, Nanog, C-Myc, Fragilis, Mvh and Stella). Then, immunocytochemical reaction was carried out for detection of marker proteins (Oct4 and Mvh). Increasing of the exposure time of the 4mT SMF (24 and 48h) and treatment time with 25ng/ml BMP4 (48 and 96h) indicated a marked decrease in expression of pluripotency genes (Oct-4, Nanog and C-Myc) and Oct4 protein and increase in primordial germ cell-specific genes (Fragilis, Mvh and Stella) and Mvh protein compared with the control group. Final results showed that in a synergistic manner, the combination of SMF with BMP4 exaggerates the differentiation potential of BMSCs to PGCs by activating the MAPK pathway and altering the Ca(2+) concentration.

Exposure to static magnetic field stimulates quorum sensing circuit in luminescent Vibrio strains of the Harveyi clade

In this study, the evidence of electron-dense magnetic inclusions with polyhedral shape in the cytoplasm of Harveyi clade Vibrio strain PS1, a bioluminescent bacterium living in symbiosis with marine organisms, led us to investigate the behavior of this bacterium under exposure to static magnetic fields ranging between 20 and 2000 Gauss. When compared to sham-exposed, the light emission of magnetic field-exposed bacteria growing on solid medium at 18°C ±0.1°C was increased up to two-fold as a function of dose and growth phase. Stimulation of bioluminescence by magnetic field was more pronounced during the post-exponential growth and stationary phase, and was lost when bacteria were grown in the presence of the iron chelator deferoxamine, which caused disassembly of the magnetic inclusions suggesting their involvement in magnetic response. As in luminescent Vibrio spp. bioluminescence is regulated by quorum sensing, possible effects of magnetic field exposure on quorum sensing were investigated. Measurement of mRNA levels by reverse transcriptase real time-PCR demonstrated that luxR regulatory gene and luxCDABE operon coding for luciferase and fatty acid reductase complex were significantly up-regulated in magnetic field-exposed bacteria. In contrast, genes coding for a type III secretion system, whose expression was negatively affected by LuxR, were down-regulated. Up-regulation of luxR paralleled with down-regulation of small RNAs that mediate destabilization of luxR mRNA in quorum sensing signaling pathways. The results of experiments with the well-studied Vibrio campbellii strain BB120 (originally classified as Vibrio harveyi) and derivative mutants unable to synthesize autoinducers suggest that the effects of magnetic fields on quorum sensing may be mediated by AI-2, the interspecies quorum sensing signal molecule.

Static magnetic fields modulate X-ray-induced DNA damage in human glioblastoma primary cells

Although static magnetic fields (SMFs) are used extensively in the occupational and medical fields, few comprehensive studies have investigated their possible genotoxic effect and the findings are controversial. With the advent of magnetic resonance imaging-guided radiation therapy, the potential effects of SMFs on ionizing radiation (IR) have become increasingly important. In this study we focused on the genotoxic effect of 80 mT SMFs, both alone and in combination with (i.e. preceding or following) X-ray (XR) irradiation, on primary glioblastoma cells in culture. The cells were exposed to: (i) SMFs alone; (ii) XRs alone; (iii) XR, with SMFs applied during recovery; (iv) SMFs both before and after XR irradiation. XR-induced DNA damage was analyzed by Single Cell Gel Electrophoresis assay (comet assay) using statistical tools designed to assess the tail DNA (TD) and tail length (TL) as indicators of DNA fragmentation. Mitochondrial membrane potential, known to be affected by IR, was assessed using the JC-1 mitochondrial probe. Our results showed that exposure of cells to 5 Gy of XR irradiation alone led to extensive DNA damage, which was significantly reduced by post-irradiation exposure to SMFs. The XR-induced loss of mitochondrial membrane potential was to a large extent averted by exposure to SMFs. These data suggest that SMFs modulate DNA damage and/or damage repair, possibly through a mechanism that affects mitochondria.

Effects of rotating magnetic field exposure on the functional parameters of different species of bacteria

The aim of the present study was to determine the effect of the rotating magnetic field (RMF) on the growth, cell metabolic activity and biofilm formation by S. aureus, E. coli, A. baumannii, P. aeruginosa, S. marcescens, S. mutans, C. sakazakii, K. oxytoca and S. xylosus. Bacteria were exposed to the RMF (RMF magnetic induction B = 25-34 mT, RMF frequency f = 5-50 Hz, time of exposure t = 60 min, temperature of incubation 37 °C). The persistence of the effect of exposure (B = 34 mT, f = 50 Hz, t = 60 min) on bacteria after further incubation (t = 300 min) was also studied. The work showed that exposure to RMF stimulated the investigated parameters of S. aureus, E. coli, S. marcescens, S. mutans, C. sakazakii, K. oxytoca and S. xylosus, however inhibited cell metabolic activity and biofilm formation by A. baumannii and P. aeruginosa. The results obtained in this study proved, that the RMF, depending on its magnetic induction and frequency can modulate functional parameters of different species of bacteria.

Hybrid magnetic scaffolds of gelatin–siloxane incorporated with magnetite nanoparticles effective for bone tissue engineering

Hybrid magnetic scaffolds of silica–gelatin-MNs newly developed to have excellent physicochemical, mechanical and biological properties that are effective for bone tissue engineering.

Effects of ELF magnetic field in combination with Iron(III) chloride (FeCl3) on cellular growth and surface morphology of Escherichia coli (E. coli)

This study investigated the effects of extremely low frequency (ELF) magnetic field with/without iron(III) chloride (FeCl3) on bacterial growth and morphology. The ELF exposures were carried out using a pair of Helmholtz coil-based ELF exposure system which was designed to generate 50 Hz sinusoidal magnetic field. The field was approximately uniform throughout the axis of the coil pair. The samples which were treated or non-treated with different concentrations FeCl3 were exposed to 50 Hz, 2 millitesla (mT) magnetic field for 24 h. ELF effect on viability was assessed in terms of viable colony counts (in colony-forming unit per milliliter) with the standard plate count technique. Scanning electron microscopy was used to investigate the magnetic field effect on surface morphology of Escherichia coli. No significant results were seen in terms of cell viability between ELF and sham-exposed bacterial strains. Similarly, FeCl3 treatment did not change cell viability of E. coli samples. However, we observed some morphological changes on E. coli cell surfaces. Pore formations and membrane destruction were seen on the surface of 24 h ELF field-exposed cells. We concluded that ELF magnetic field exposure at 2 mT does not affect cell viability; however, it may affect bacterial surface morphology.

Electromagnetic fields enhance chondrogenesis of human adipose-derived stem cells in a chondrogenic microenvironment in vitro

We tested the hypothesis that electromagnetic field (EMF) stimulation enhances chondrogenesis in human adipose-derived stem cells (ADSCs) in a chondrogenic microenvironment. A two-dimensional hyaluronan (HA)-coated well (2D-HA) and a three-dimensional pellet culture system (3D-pellet) were used as chondrogenic microenvironments. The ADSCs were cultured in 2D-HA or 3D-pellet, and then treated with clinical-use pulse electromagnetic field (PEMF) or the innovative single-pulse electromagnetic field (SPEMF) stimulation. The cytotoxicity, cell viability, and chondrogenic and osteogenic differentiations were analyzed after PEMF or SPEMF treatment. The modules of PEMF and SPEMF stimulations used in this study did not cause cytotoxicity or alter cell viability in ADSCs. Both PEMF and SPEMF enhanced the chondrogenic gene expression (SOX-9, collagen type II, and aggrecan) of ADSCs cultured in 2D-HA and 3D-pellet. The expressions of bone matrix genes (osteocalcin and collagen type I) of ADSCs were not changed after SPEMF treatment in 2D-HA and 3D-pellet; however, they were enhanced by PEMF treatment. Both PEMF and SPEMF increased the cartilaginous matrix (sulfated glycosaminoglycan) deposition of ADSCs. However, PEMF treatment also increased mineralization of ADSCs, but SPEMF treatment did not. Both PEMF and SPEMF enhanced chondrogenic differentiation of ADSCs cultured in a chondrogenic microenvironment. SPEMF treatment enhanced ADSC chondrogenesis, but not osteogenesis, when the cells were cultured in a chondrogenic microenvironment. However, PEMF enhanced both osteogenesis and chondrogenesis under the same conditions. Thus the combination of a chondrogenic microenvironment with SPEMF stimulation can promote chondrogenic differentiation of ADSCs and may be applicable to articular cartilage tissue engineering.