Escherichia coli Growth Changes by the Mediated Effects After Low-Intensity Electromagnetic Irradiation of Extremely High Frequencies

Water is the major constituent of environmental medium and biological systems. The effects occurring in water as a result of low-intensity electromagnetic irradiation (EMI) in extremely high frequencies are supposed to be the primary mechanism to create conditions for biological responses. The EMI effects on Escherichia coli, after irradiation of their suspension, are most probably water-mediated. Indirect effects of EMI at 51.8, 53, 70.6, and 73 GHz frequencies on bacteria, through water, assay buffer (Tris–phosphate buffer with inorganic salts at low or moderate concentrations), or peptone growth medium were studied. The mediated effects of 70.6 and 73 GHz irradiated water, assay buffer, and growth medium on E. coli growth characteristics were insignificant. But the results were different for 51.8 and 53 GHz. EMI mediated effects on bacterial growth were clearly demonstrated. The effects were more strongly expressed with 53 GHz. Moreover, it was shown that 70.6 and 73 GHz similarly suppressed the cell growth after direct irradiation of E. coli in water or on solid medium. Interestingly, for 51.8 and 53 GHz the bacterial growth decreases after suspension irradiation was less, compared to the direct irradiation of bacteria on solid medium. Especially, it was also more expressed in case of 53 GHz. Also with electron microscopy, EMI-induced bacterial cell sizes and structure different changes were detected. In addition, the distinguished changes in surface tension, oxidation–reduction potential and pH of water, assay buffer, growth medium, and bacterial suspension were determined. They depended on EMI frequency used. The differences could be associated with the partial absorbance of EMI energy by the surrounding medium, which depends on a specific frequency. The results are crucial to understand biophysical mechanisms of EMI effects on bacteria.     

The action of low-intensity extremely high-freguency electromagnetic radiation on growth parameters for bacteria Enterococcus hirae

It has been found that the exposure of Enterococcus hirae ATCC9790, grown under anaerobic conditions for 30 min or 1 h, to low-intensity (flux capacity 0.06 mW/sm2) coherent electromagnetic radiation (EMI) of extremely high-frequency 45 - 53 GHz), or millimeter waves causes a marked prolongation of the lag-growth phase and a decrease in their specific growth rate, the inhibitory effect increasing in the frequency range from 49 to 53 GHz. The effect enhanced as duration of expocure was encreased from 30 min to 1 h; however, further increase in exposure duration to 2 h did not cause an enhancement of the effect. It has been shown that the action of extremely high-frequency EMI on these bacteria does not depend on medium pH (pH 8.0 or pH 6.0). It is proposed that these bacteria have defensive or reparation mechanisms which compensate for the action of radiation; the occurrence of different mechanisms for pH regulation is not ruled out.     

Extremely High Frequency Electromagnetic Irradiation in Combination with Antibiotics Enhances Antibacterial Effects on Escherichia coli

Antibacterial effects of the electromagnetic irradiation (EMI) of 51.8 and 53 GHz frequencies with low intensity (the flux capacity of 0.06 mW/cm(2)) and non-thermal action were investigated upon direct irradiation of E. coli K12. Significant decrease in bacterial growth rate and in the number of viable cells, marked change in H(+) and K(+) transport across membrane were shown. Subsequent addition of kanamycin or ceftriaxone (15 or 0.4 μM, respectively) enhanced the effects of irradiation. This was maximally achieved at the frequency of 53 GHz. These all might reveal membrane as probable target for antibacterial effects. Apparently, the action of EMI on bacteria might lead to changed membrane properties and to antibiotic resistance. The results should improve using extremely high frequency EMI in combination with antibiotics in biotechnology, therapeutic practice, and food industry.     

Changes in ion transport through membranes, ATPase activity and antibiotics effects in Enterococcus hirae after low intensity electromagnetic irradiation of 51.8 and 53.0 GHz frequencies

It was ascertained that one-hour exposure of Enterococcus hirae ATCC9790 bacteria grown under anaerobic condition during sugar (glucose) fermentation to coherent electromagnetic irradiation (EMI) of 51.8 and 53.0 GHz frequencies or millimeter waves (5.79 and 5.66 mm wavelengths) of low-intensity (flux capacity of 0.06 mW/cm²) caused a significant decrease in energy-dependent H⁺ and K⁺ transports across the membranes of whole cells. Therewith, K⁺ influx into cells was appreciably less at the frequency of 53.0 GHz. Likewise, a significant decrease of total and N,N′-dicyclohexylcarbodiimide-sensitive ATPase activity of the membrane vesicles occurred after EMI of 51.8 and 53.0 GHz. These results indicated the input of membranous changes in bacterial action of low intensity extremely high frequency EMI, when the F₀F₁-ATPase was probably playing a key role. Additionally, the enhancement of the effects of antibiotics — ceftriaxone, kanamycin and ampicillin at their minimal inhibitory concentrations (100, 200 and 1.4 μM, correspondingly) on the bacterial growth by these irradiations was shown. Also, combined action of EMI and antibiotics depressed strongly H⁺ and K⁺ fluxes across membrane. Especially, H⁺ flux was more sensitive to the action of ceftriaxone, but K⁺ flux was sensitive to kanamycin. All these made the assumption that EMI of 51.8 and 53.0 GHz frequencies, especially 53.0 GHz, was followed by change in bacterial sensitivity toward antibiotics that was more obvious with ceftriaxone and ampicillin.     

Low Intensity Electromagnetic Irradiation with 70.6 and 73 GHz Frequencies Affects <Emphasis Type="Italic">Escherichia coli</Emphasis> Growth and Changes Water Properties

The low intensity electromagnetic irradiation (EMI) of the 70.6 and 73 GHz frequency is resonant for Escherichia coli but not for water. In this study, E. coli irradiation with this EMI during 1 h directly and in bi-distilled water or in the assay buffer with those frequencies resulted with noticeable changes in bacterial growth parameters. Furthermore, after EMI, 2 h rest of bacteria renewed their growth in 1.2-fold, but repeated EMI—had no significant action. Moreover, water absorbance, pH, and electric conductance were changed markedly after such irradiation. The results point out that EMI of the 70.6 and 73 GHz frequency can interact with bacteria affecting growth and in the same time with the surrounding medium (water) as well.     

The effect of low-intensity coherent extremely high frequency electromagnetic radiation on growth parameters for <Emphasis Type="Italic">Enterococcus hirae</Emphasis> bacteria

It is found that for Enterococcus hirae ATCC9790 bacteria grown in anaerobic conditions, one-hour exposure to low-intensity (radiant power of 0.06 mW/cm²) coherent extremely high frequency electromagnetic radiation (from 45 to 53 GHz), or millimeter electromagnetic radiation, leads to an appreciable increase in latent growth time and to a decrease in specific growth rate; herein, the effects intensify as the frequency increases from 49 to 53 GHz. The result is enhanced at an increase in the radiation duration from 30 min to 1 h; however, a further increase in the exposure time up to 2 h does not lead to intensification of the effect. It is shown that the effect of extremely high frequency electromagnetic radiation on Enterococcus hirae does not depend on pH of the medium (pH 6.0 or 8.0). It may be expected that these bacteria have protective or reparation mechanisms that compensate long-term action of this radiation; it is not improbable that various mechanisms of pH regulation are present as well.     

<Emphasis Type="Italic">Escherichia coli</Emphasis> Membrane-Associated Energy-Dependent Processes and Sensitivity Toward Antibiotics Changes as Responses to Low-Intensity Electromagnetic Irradiation of 70.6 and 73 GHz Frequencies

Escherichia coli K-12(λ) was sensitive toward low-intensity (non-thermal, flux capacity 0.06 mW cm⁻²) electromagnetic irradiation (EMI) of extremely high frequency—70.6 and 73 GHz. 1 h exposure to EMI markedly depressed growth and cell viability of bacteria. Membrane-associated processes—total H⁺ efflux and H₂ evaluation by whole cells during glucose fermentation were shown to be lowered as well. At the same time, the F₀F₁-ATPase activity of membrane vesicles was little depressed with 70.6 GHz irradiation only. This finding was in conformity with non-changed N,N′-dicyclohexylcarbodiimide-sensitive H⁺ efflux. Furthermore, for understanding the different frequencies action mechanisms, the effects of antibiotics (chloramphenicol, ceftriaxone, kanamycin, and tetracycline) on irradiated cells growth and survival were determined. EMI with the frequencies of 70.6 and 73 GHz as with 51.8 and 53.0 GHz enhanced the sensitivity of bacteria toward antibiotics, but comparison revealed that each frequency had a different portion. Probably, EMI of specific frequency triggered changes in biological processes and afterward in growth and viability of bacteria, creating conditions when the action of antibiotics became facilitated.     

Indirect and repeated electromagnetic irradiation of extremely high freguency of bacteria Escherichia coli

It has been shown that separate irradiation of distilled water and tris-phosphate buffer containing some inorganic ions, with Escherichia coli K12 grown in anaerobic conditions upon fermentation of sugar (glucose) with "noise" electromagnetic radiation of extremely high frequencies (53.5-68 gHz) or millimeter waves (wavelength of 3 to 8 mm) with low flux capacity (0.01 mW) for 10, 30 and 60 min caused opposite effects, changing the growth of these bacteria. The irradiation of water has a bactericide effect, whereas the irradiation of the buffer stimulates bacterial growth although the buffer itself inhibits the growth. These results point out the role of water in the bactericide action of "noise" electromagnetic radiation of extremely high frequencies, and confirm the significance of membranotropic effects. The bactericide action disappeared after repeated irradiation for 10 and 30 min with 2-h intervals. This indicates the operation of some compensatory mechanisms in bacteria.     

Electromagnetic irradiation of Enterococcus hirae at low-intensity 51.8- and 53.0-GHz frequencies: changes in bacterial cell membrane properties and enhanced antibiotics effects

Exposure to electromagnetic irradiation (EMI) of 51.8 and 53.0?GHz and low intensity (flux capacity of 0.06?mW?cm(-2) ) for 1?h markedly decreased the energy-dependent H(+) and K(+) transport across membranes of Enterococcus hirae ATCC 9790. After EMI, there was also a significant decrease of overall and N,N'-dicyclohexylcarbodiimide (DCCD)-sensitive ATPase activity of the membrane vesicles. These measures were considerably lower at 53.0 GHz. EMI in combination with different antibiotics, such as ceftriaxone and kanamycin at their minimal inhibitory concentrations (100 and 200?μM, respectively), enhanced bacterial cell growth and altered their membrane transport properties. Total H(+) efflux was most sensitive to ceftriaxone but DCCD-inhibited H(+) efflux and total K(+) influx were sensitive to kanamycin. The results indicate that cell membrane proteins could be a target in the action of EMI and enhanced antibacterial effects in combination with antibiotics. The DCCD-sensitive F(0) F(1) -ATPase or this ATPase in combination with K(+) uptake protein probably plays a key role in these effects.     

The Effect of Electromagnetic Radiation at Frequencies of 51.8 and 53.0 GHz on Growth,Pigment Content,Hydrogen Photoemission,and F<Subscript>0</Subscript>F<Subscript>1</Subscript>-ATPase Activity in the Purple Bacterium <Emphasis Type="Italic">Rhodobacter sphaeroides</Emphasis>

Exposure of the purple bacteria Rhodobacter sphaeroides MDC6522 isolated from Jermuk mineral springs (Armenia) to extremely high-frequency electromagnetic radiation (51.8 and 53.0 GHz) for 15 min resulted in a pronounced increase in the specific growth rate and H₂ photoemission. However, a significant decrease in the specific growth rate (1.6–2.0 times) was observed when the duration of irradiation was prolonged to 1 h. The maximum effect was at a frequency of 53.0 GHz. During irradiation for 1 h, absorption maxima typical of carotenoids gradually disappeared, and the level of bacteriochlorophyll а complexes decreased. Prolonged irradiation also inhibited the H₂ production during bacterial growth for 72 h, although it was restored after 96 h of growth. The activity of N,N'-dicyclohexylcarbodiimide-sensitive proton F₀F₁- ATPase also decreased in Rh. sphaeroides. These results indicate that the membrane-bound F₀F₁-ATPase may be the main target of action of extremely-high-frequency electromagnetic radiation. The data we obtained can be used in biotechnology for control of growth and hydrogen metabolism of phototrophic bacteria.     

Extremely High Frequency Electromagnetic Radiation Enforces Bacterial Effects of Inhibitors and Antibiotics

The coherent electromagnetic radiation (EMR) of the frequency of 51.8 and 53 GHz with low intensity (the power flux density of 0.06 mW/cm(2)) affected the growth of Escherichia coli K12(lambda) under fermentation conditions: the lowering of the growth specific rate was considerably (approximately 2-fold) increased with exposure duration of 30-60 min; a significant decrease in the number of viable cells was also shown. Moreover, the enforced effects of the N,N'-dicyclohexylcarbodiimide (DCCD), inhibitor of H(+)-transporting F(0)F(1)-ATPase, on energy-dependent H(+) efflux by whole cells and of antibiotics like tetracycline and chloramphenicol on the following bacterial growth and survival were also determined after radiation. In addition, the lowering in DCCD-inhibited ATPase activity of membrane vesicles from exposed cells was defined. The results confirmed the input of membranous changes in bacterial action of low intensity extremely high frequency EMR, when the F(0)F(1)-ATPase is probably playing a key role. The radiation of bacteria might lead to changed metabolic pathways and to antibiotic resistance. It may also give bacteria with a specific role in biosphere.     

Low-intensity electromagnetic irradiation of 70.6 and 73 GHz frequencies enhances the effects of disulfide bonds reducer on Escherichia coli growth and affects the bacterial surface oxidation-reduction state

Low-intensity electromagnetic irradiation (EMI) of 70.6 and 73 GHz frequencies (flux capacity – 0.06 mW cm⁻²) had bactericidal effects on Escherichia coli. This EMI (1 h) exposure suppressed the growth of E. coli K-12(λ). The pH value (6.0–8.0) did not significantly affect the growth. The lag-phase duration was prolonged, and the growth specific rate was inhibited, and these effects were more noticeable after 73 GHz irradiation. These effects were enhanced by the addition of DL-dithiothreitol (DTT), a strong reducer of disulfide bonds in surface membrane proteins, which in its turn also has bactericidal effect. Further, the number of accessible SH-groups in membrane vesicles was markedly decreased by EMI that was augmented by N,N′-dicyclohexycarbodiimide and DTT. These results indicate a change in the oxidation–reduction state of bacterial cell membrane proteins that could be the primary membranous mechanism in the bactericidal effects of low-intensity EMI of the 70.6 and 73 GHz frequencies.     

Comparable Effects of Low-intensity Electromagnetic Irradiation at the Frequency of 51.8 and 53 GHz and Antibiotic Ceftazidime on Lactobacillus acidophilus Growth and Survival

The effects of low-intensity electromagnetic irradiation (EMI) with the frequencies of 51.8 and 53 GHz on Lactobacillus acidophilus growth and survival were revealed. These effects were compared with antibacterial effects of antibiotic ceftazidime. Decrease in bacterial growth rate by EMI was comparable with the inhibitory effect of ceftazidime (minimal inhibitory concentration—16 μM) and no enhanced action was observed with combined effects of EMI and the antibiotic. However, EMI-enhanced antibiotic inhibitory effect on bacterial survival. The kinetics of the bacterial suspension oxidation–reduction potential up to 24 h of the growth was changed by EMI and ceftazidime. The changes were more strongly expressed by combined effects of EMI and antibiotic especially up to 12 h. Moreover, EMI did not change overall energy (glucose)-dependent H⁺ efflux across the membrane but it increased N,N′-dicyclohexylcarbodiimide (DCCD)-inhibited H⁺ efflux. In contrast, this EMI in combination with ceftazidime decreased DCCD-sensitive H⁺ efflux. Low-intensity EMI had inhibitory effect on L. acidophilus bacterial growth and survival. The effect on bacterial survival was more significant in the combination with ceftazidime. The H⁺-translocating F ₀ F ₁-ATPase, for which DCCD is specific inhibitor, might be a target for EMI and ceftazidime. The revealed bactericide effects on L. acidophilus can be applied in biotechnology, food producing and safety technology.     

Escherichia coli membrane proton conductance and proton efflux depend on growth pH and are sensitive to osmotic stress

The dependence of Escherichia coli membrane H+ conductance (Gm H+) with a steady-state pH in the presence and absence of an external source of energy (glucose) was studied, when cells were grown under anaerobic and aerobic conditions, with an assay pH of 7.0. Energy-dependent H+ efflux by intact cells growing at pH of 4.5-7.5 was also measured. The elevated H+ conductance and lowered H+ flux were shown for cells growing in acidic pH and under anaerobic conditions, when bacteria were fermenting glucose. The atp mutant, which is deprived of the F0F1- adenosine triphosphatase, had less Gm H+ independent of growth conditions. In contrast with wild-type or precursor strain, a remarkable difference in Gm H+ for atp mutant was observed between aerobic and anaerobic conditions; such a difference was significant at pH 4.5. These results could indicate distinguishing pathways determining Gm H+ under anaerobic conditions after the fermentation of glucose at different pH and an input of the F0F1-adenosine triphosphatase in Gm H+. In addition, the effect of osmotic stress was demonstrated with grown cells. Gm H+ and H+ efflux both were increased after hyperosmotic stress at pH 7.5, and these changes were inhibited by N,N\'-dicyclohexylcarbodiimide, whereas these changes were lower in atp mutant. A role of the F0F1-adenosine triphosphatase in osmo-sensitivity of bacteria was confirmed under fermentative conditions.     

The influence of incubation temperature and pH on the antimicrobial properties of hen egg albumen

T ranter H.S. & B oard , R.G. 1984. The influence of incubation temperature and pH on the antimicrobial properties of hen egg albumen. Journal of Applied Bacteriology 56 , 53–6.
Gram positive bacteria, including lysozyme-resistant strains, and yeasts were killed in hen egg albumen with or without iron at 30 of 39.5.dGC. The albumen was more toxic at 39.5.dGC than at 30C for Gram negative bacteria. With the exceptions of Pseudomonas fluorescens, Acinetobacter sp. and Proteus vulgaris , iron caused the growth of Gram negative bacteria or protected them from being killed in hen albumen at 39.5.dGC. At this temperature, however, maximal growth of and glucose utilization by Escherichia coli C20 only occurred in albumen supplemented with growth factors, trace metals, additional nitrogen and sufficient iron to quench ovotransferrin. The bactericidal properties of albumen could be negated by changing its pH from 90 or above to 7.5 or below. At 39.5C, enterochelin allowed growth of E. coli in albumen at pH 7.9, but not at 9.4, whereas iron allowed growth at both pH values.     

Effects of the microwave exposure at elevated ambient temperature on the thermo-compensatory responses of small laboratory animals

Thermogenic effectiveness of electromagnetic irradiation (EMI) of UHF range (7 GHz) in the dependence on intensity (10-50 mW/cm2) and environmental temperature (22 degrees and 30 degrees C) was studied in experiments with mice and rats. Negative influence of high ambient temperature on thermoregulate responses of animals at microwave exposure was showed. It is concluded that this interaction should been taken into account for hygienic standardization of non-ionizing EMI.     

Anti-inflammatory effects of low-intensity extremely high-frequency electromagnetic radiation: frequency and power dependence

Using a model of acute zymosan-induced footpad edema in NMRI mice, the frequency and power dependence of anti-inflammatory effect of low-intensity extremely high-frequency electromagnetic radiation (EHF EMR) was found. Single whole-body exposure of animals to EHF EMR at the intensity of 0.1 mW/cm(2) for 20 min at 1 h after zymosan injection reduced both the footpad edema and local hyperthermia on average by 20% at the frequencies of 42.2, 51.8, and 65 GHz. Some other frequencies from the frequency range of 37.5-70 GHz were less effective or not effective at all. At fixed frequency of 42.2 GHz and intensity of 0.1 mW/cm(2), the effect had bell-shaped dependence on exposure duration with a maximum at 20-40 min. Reduction of intensity to 0.01 mW/cm(2) resulted in a change of the effect dependence on exposure duration to a linear one. Combined action of cyclooxygenase inhibitor sodium diclofenac and EHF EMR exposure caused a partial additive effect of decrease in footpad edema. Combined action of antihistamine clemastine and EHF EMR exposure caused a dose-dependent abolishment of the anti-inflammatory effect of EHF EMR. The results obtained suggest that arachidonic acid metabolites and histamine are involved in realization of anti-inflammatory effects of low-intensity EHF EMR.     

Effect of Growth pH on the Phospholipid Contents of the Membranes from Alkaliphilic Bacteria

An aerobic alkaliphile YN-2000 and a facultatively anaerobic alkaliphile BL77/1 are able to grow over the wide pH range of 7–10.5. Net surface charges on the membranes from YN-2000 and BL77/1 were negative above pH 4, and the amounts were significantly increased when the bacteria were cultured at pH 10 as compared with those cultured at pH 7.5. Phospholipid contents of the membranes from both bacteria grown at pH 10 were much higher than those from the bacteria grown at pH 7.5. Phospholipids of the membranes from YN-2000 and BL77/1 were composed mainly of cardiolipin (CL), phosphatidylethanolamine (PE), and phosphatidylglycerol (PG). It is suggested that the increases by growth at pH 10 of negative charges on the membranes from the bacteria result mainly from the increases of acidic phospholipids such as CL and PG. Increases of phospholipid contents and/or negative charges on the membranes seem to contribute to the adaptation of YN-2000 and BL77/1 to an alkaline environment. Received: 13 May 1999 / Accepted: 14 June 1999     

The effect of citric acid on growth of proteolytic strains of Clostridium botulinum

In strictly anaerobic conditions in a culture medium adjusted to pH 5.2 with HCl and incubated at 30 degrees C, inocula containing less than 10 vegetative bacteria of Clostridium botulinum ZK3 (type A) multiplied to give greater than 10(8) bacteria per ml in 3 d. Growth from an inoculum of between 10 and 100 spores occurred after a delay of 10-20 weeks. Citric acid concentrations of 10-50 mmol/l at pH 5.2 inhibited growth from both vegetative bacteria and spore inocula, a concentration of 50 mmol/l increasing the number of vegetative bacteria or of spores required to produce growth by a factor of approximately 10(6). The citric acid also reduced the concentration of free Ca2+ in the medium. The inhibitory effect of citric acid on vegetative bacteria at pH 5.2 could be prevented by the addition of Ca2+ or Mg2+ and greatly reduced by Fe2+ and Mn2+. The addition of Ca2+, but not of the remaining divalent metal ions, restored the concentration of free Ca2+ in the medium to that in the citrate-free medium. The inhibitory effect of citric acid on growth from a spore inoculum was only partially prevented by Ca2+. Citric acid (50 mmol/l) did not inhibit growth of strain ZK3 at pH 6 despite the greater chelating activity of citrate at pH 6 than at pH 5.2. The effect of citric acid and Ca2+ at pH 5.2 on vegetative bacteria of strains VL1 (type A) and 2346 and B6 (proteolytic type B) was similar to that on strain ZK3.     

Inhibition of type A and type B (proteolytic) Clostridium botulinum by sorbic acid

The effect of sorbic acid in the pH range 4.9 to 7.0 on the probability P of growth of a single vegetative bacterium of proteolytic strains of Clostridium botulinum has been determined by comparison of the most probable number count of the bacteria in media at pH 4.9 to 7.0 containing a series of concentrations of potassium sorbate and in a nutrient medium at pH 6.8 to 7.0. The media were maintained under strictly anaerobic conditions at a redox potential equivalent to lower than -350 mV at pH 7. In medium adjusted to the required pH with HCl, P for strain ZK3 (type A) at pH 5.1 or 5.5 after 2 days at 30 degrees C was similar to that at pH 6.8 to 7.0 but was slightly lower at pH 4.9. Potassium sorbate inhibited growth, the inhibition being a function of the concentration of undissociated sorbic acid. A calculated undissociated sorbic acid concentration of 156 mg/liter delayed growth of strain ZK3 (type A) but did not result in a significant decrease in P after an incubation time of 14 days. Higher concentrations of undissociated sorbic acid caused longer delays before maximum most probable number counts developed, and a calculated undissociated sorbic acid concentration of 282 mg/liter decreased log P for strain ZK3 after an incubation time of 14 days by a factor of 5.5 to 7.5. Four additional type A strains and five type B strains were inhibited to an extent comparable to inhibition of strain ZK3.(ABSTRACT TRUNCATED AT 250 WORDS)