The Influence of Low Magnetic Fields and Magnesium Isotopes on <Emphasis Type="Italic">E. coli</Emphasis> Bacteria

The combined effects of external low static magnetic fields at 0–22 mT and magnesium isotopes on the growth and development of E. coli bacteria has been studied. The magnetic field and ²⁵Mg magnetic isotope effects were obtained in two ranges: 0.8–3.0 and 8–13 mT. The experimental values of the growth rate, the number of CFUs and the ATP pool of bacteria enriched in magnetic magnesium isotope ²⁵Mg (nuclear spin, I = 5/2) in the range of 0.8–3.0 mT are significantly higher compared to bacteria enriched in nonmagnetic isotopes ²⁴Mg, ²⁶Mg, or natural magnesium. The increase in the growth rate, colony-forming ability, and intracellular ATP concentration in bacteria in all groups cultivated under exposure to an external static magnetic field in the range of 0.8 to 3.0 mT confirms the existence of magnetosensitive stages of enzymatic reactions that proceed via the ion-radical mechanism. The combined influence of the magnetic field in the range of 8 to 13 mT and the magnesium magnetic isotope ²⁵Mg on the colony forming ability of E. coli bacteria is associated with processes that are responsible for cell division. The above-mentioned effects of bacterial magnetosensitivity (to magnetic fields and magnetic isotopes) are in good agreement with theoretical predictions of the theory of spin-dependent enzymatic reactions.     

Magnetosensitivity of <Emphasis Type="Italic">E. coli</Emphasis> Bacteria in the Presence of Zinc Isotopes

The combined effect of the zinc magnetic isotope ⁶⁷Zn and weak magnetic field 25–35 mT causes a 2–4-fold increase in the colony-forming ability of bacteria E. coli in comparison with the nonmagnetic isotopes ^{64, 66}Zn. The effects of magnetic field in the range of 2.2–8 mT were detected for all bacteria regardless of the zinc-isotope enrichment of the media. This indicates the sensitivity of intracellular processes to weak magnetic fields. An increase in the ATP concentration in E. coli cells was only detected for the bacteria grown on the medium with the magnetic zinc isotope in the range of 2.2–4.2 mT. The obtained data confirm the existence of stages of intracellular enzymatic processes that are sensitive to magnetic fields and magnetic moments of atomic nuclei.     

Magnetic isotope effect of magnesium <Superscript>25</Superscript>Mg on <Emphasis Type="Italic">E. coli</Emphasis> resistance to antibiotics

Effects of synergism and antagonism of antibacterial drugs and magnetic isotope of magnesium ²⁵Mg on antibiotic resistance of bacteria E. coli were discovered. Fourteen antibiotics from seven different groups were tested. The increase in antibiotic resistance in the presence of the ion ²⁵Mg²⁺ was discovered in E. coli cells incubated with quinolones/fluoroquinolones, indicating the inhibiting effect of the magnetic moments of nuclei ²⁵Mg on DNA synthesis. The change in antibiotic resistance was also detected in bacteria affected by magnesium ²⁵Mg and certain antibiotics from aminoglycoside and lincosamide groups.     

<Emphasis Type="Italic">Candida krusei</Emphasis> isolated from fruit juices ultrafiltration membranes promotes colonization of <Emphasis Type="Italic">Escherichia coli</Emphasis> O157:H7 and <Emphasis Type="Italic">Salmonella enterica</Emphasis> on stainless steel surfaces

To clarify the interactions between a common food spoilage yeast and two pathogenic bacteria involved in outbreaks associated with fruit juices, the present paper studies the effect of the interplay of Candida krusei, collected from UF membranes, with Escherichia coli O157:H7 and Salmonella enterica in the overall process of adhesion and colonization of abiotic surfaces. Two different cases were tested: a) co-adhesion by pathogenic bacteria and yeasts, and b) incorporation of bacteria to pre-adhered C. krusei cells. Cultures were made on stainless steel at 25°C using apple juice as culture medium. After 24 h of co-adhesion with C. krusei, both E. coli O157:H7 and S. enterica increased their counts 1.05 and 1.11 log CFU cm², respectively. Similar increases were obtained when incorporating bacteria to pre-adhered cells of Candida. Nevertheless C. krusei counts decreased in both experimental conditions, in a) 0.40 log CFU cm² and 0.55 log CFU cm² when exposed to E. coli O157:H7 and S. enterica and in b) 0.18 and 0.68 log CFU cm², respectively. This suggests that C. krusei, E. coli O157:H7, and S. enterica have a complex relationship involving physical and chemical interactions on food contact surfaces. This study supports the possibility that pathogen interactions with members of spoilage microbiota, such as C. krusei, might play an important role for the survival and dissemination of E. coli O157:H7 and Salmonella enterica in food-processing environments. Based on the data obtained from the present study, much more attention should be given to prevent the contamination of these pathogens in acidic drinks.     

Cyclohexanone-induced stress metabolism of <Emphasis Type="Italic">Escherichia coli</Emphasis> and <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis>

Solvent stress occurs during whole-cell biocatalysis of organic chemicals. Organic substrates and/or products may accumulate in the cellular membranes of whole cells, causing structural destabilization of the membranes, which leads to disturbances in cellular carbon and energy metabolism. Here, we investigate the effect of cyclohexanone on carbon metabolism in Escherichia coli BL21 and Corynebacterium glutamicum ATCC13032. Adding cyclohexanone to the culture medium (i.e., glucose mineral medium) resulted in a decreased specific growth rate and increased cellular maintenance energy in both strains of bacteria. Notably, carbon metabolism, which is mainly involved to increase cellular maintenance energy, was very different between the bacteria. Carbon flux into the acetic acid fermentation pathway was dominantly enhanced in E. coli, whereas the TCA cycle appeared to be activated in C. glutamicum. In fact, carbon flux into the TCA cycle in E. coli appeared to be reduced with increasing amounts of cyclohexanone in the culture medium. Metabolic engineering of E. coli cells to maintain or improve TCA cycle activity and, presumably, that of the electron transport chain, which are involved in regeneration of cofactors (e.g., NAD(P)H and ATP) and formation of toxic metabolites (e.g., acetic acid), may be useful in increasing solvent tolerance and biotransformation of organic chemicals (e.g., cyclohexanone).     

Dual-species biofilm of <Emphasis Type="Italic">Listeria monocytogenes</Emphasis> and <Emphasis Type="Italic">Escherichia coli</Emphasis> on stainless steel surface

Listeria monocytogenes is a Gram-positive bacterium commonly associated with foodborne diseases. Due its ability to survive under adverse environmental conditions and to form biofilm, this bacterium is a major concern for the food industry, since it can compromise sanitation procedures and increase the risk of post-processing contamination. Little is known about the interaction between L. monocytogenes and Gram-negative bacteria on biofilm formation. Thus, in order to evaluate this interaction, Escherichia coli and L. monocytogenes were tested for their ability to form biofilms together or in monoculture. We also aimed to evaluate the ability of L. monocytogenes 1/2a and its isogenic mutant strain (ΔprfA ΔsigB) to form biofilm in the presence of E. coli. We assessed the importance of the virulence regulators, PrfA and σ^B, in this process since they are involved in many aspects of L. monocytogenes pathogenicity. Biofilm formation was assessed using stainless steel AISI 304 #4 slides immersed into brain heart infusion broth, reconstituted powder milk and E. coli preconditioned medium at 25 °C. Our results indicated that a higher amount of biofilm was formed by the wild type strain of L. monocytogenes than by its isogenic mutant, indicating that prfA and sigB are important for biofilm development, especially maturation under our experimental conditions. The presence of E. coli or its metabolites in preconditioned medium did not influence biofilm formation by L. monocytogenes. Our results confirm the possibility of concomitant biofilm formation by L. monocytogenes and E. coli, two bacteria of major significance in the food industry.     

Conjugative plasmid transfer from <Emphasis Type="Italic">Escherichia coli</Emphasis> is a versatile approach for genetic transformation of thermophilic <Emphasis Type="Italic">Bacillus</Emphasis> and <Emphasis Type="Italic">Geobacillus</Emphasis> species

We previously demonstrated efficient transformation of the thermophile Geobacillus kaustophilus HTA426 using conjugative plasmid transfer from Escherichia coli BR408. To evaluate the versatility of this approach to thermophile transformation, this study examined genetic transformation of various thermophilic Bacillus and Geobacillus spp. using conjugative plasmid transfer from E. coli strains. E. coli BR408 successfully transferred the E. coli–Geobacillus shuttle plasmid pUCG18T to 16 of 18 thermophiles with transformation efficiencies between 4.1 × 10^?7 and 3.8 × 10^?2/recipient. Other E. coli strains that are different from E. coli BR408 in intracellular DNA methylation also generated transformants from 9 to 15 of the 18 thermophiles, including one that E. coli BR408 could not transform, although the transformation efficiencies of these strains were generally lower than those of E. coli BR408. The conjugation was performed by simple incubation of an E. coli donor and a thermophile recipient without optimization of experimental conditions. Moreover, thermophile transformants were distinguished from abundant E. coli donor only by high temperature incubation. These observations suggest that conjugative plasmid transfer, particularly using E. coli BR408, is a facile and versatile approach for plasmid introduction into thermophilic Bacillus and Geobacillus spp., and potentially a variety of other thermophiles.     

Analysis of an N-terminal deletion in subunit <Emphasis Type="Italic">a</Emphasis> of the <Emphasis Type="Italic">Escherichia coli</Emphasis> ATP synthase

Subunit a is a membrane-bound stator subunit of the ATP synthase and is essential for proton translocation. The N-terminus of subunit a in E. coli is localized to the periplasm, and contains a sequence motif that is conserved among some bacteria. Previous work has identified mutations in this region that impair enzyme activity. Here, an internal deletion was constructed in subunit a in which residues 6–20 were replaced by a single lysine residue, and this mutant was unable to grow on succinate minimal medium. Membrane vesicles prepared from this mutant lacked ATP synthesis and ATP-driven proton translocation, even though immunoblots showed a significant level of subunit a. Similar results were obtained after purification and reconstitution of the mutant ATP synthase into liposomes. The location of subunit a with respect to its neighboring subunits b and c was probed by introducing cysteine substitutions that were known to promote cross-linking: a_L207C + c_I55C, a_L121C + b_N4C, and a_T107C + b_V18C. The last pair was unable to form cross-links in the background of the deletion mutant. The results indicate that loss of the N-terminal region of subunit a does not generally disrupt its structure, but does alter interactions with subunit b.     

The dependence of intracellular ATP level on the nutrition mode of the acidophilic bacteria <Emphasis Type="Italic">Sulfobacillus thermotolerans</Emphasis> and <Emphasis Type="Italic">Alicyclobacillus tolerans</Emphasis>

The dynamics of the ATP pool in the aerobic spore-forming acidothermophilic mixotrophic bacteria Sulfobacillus thermotolerans Kr1^T and Alicyclobacillus tolerans K1^T were studied in the course of their chemolithoheterotrophic, chemoorganoheterotrophic, and chemolithoautotrophic growth. It was established that, during mixotrophic growth, the maximum ATP concentrations in the cells of S. thermotolerans Kr1 and A. tolerans K1 were 3.8 and 0.6 nmol/mg protein, respectively. The ATP concentrations in sulfobacilli and alicyclobacilli during organotrophic growth were 2.2 and 3.1 nmol/mg protein, respectively. In the cells of the obligately heterotrophic bacterium Alicyclobacillus cycloheptanicus 4006^T, the maximum ATP concentration was several times higher and reached 12.3 nmol/mg protein. During lithotrophic growth, the maximum values of the ATP concentration in the cells of S. thermotolerans Kr1 and A. tolerans K1 were 0.3 and <0.1 nmol/mg protein, respectively; in the cells of the autotrophic bacterium Acidithiobacillus ferrooxidans TFBk, the ATP content was about 60–300 times higher (17.0 nmol/mg protein). It is concluded that low ATP content is among the possible causes of growth cessation of S. thermotolerans Kr1 and A. tolerans K1 under auto-and heterotrophic conditions after several culture transfers.     

Effects of Colistin and Bacteriocins Combinations on the In Vitro Growth of <Emphasis Type="Italic">Escherichia coli</Emphasis> Strains from Swine Origin

Escherichia coli strains from swine origin, either susceptible or resistant to colistin, were grown under planktonic and biofilm cultures. After which, they were treated with antibacterial agents including nisin and enterocin DD14 bacteriocins, colistin and their combinations. Importantly, the combination of colistin, enterocin DD14 and nisin eradicated the planktonic and biofilm cultures of E. coli CIP54127 and the E. coli strains with colistin-resistance phenotype such as E. coli 184 (mcr-1 ⁺) and E. coli 289 (mcr-1 ^?), suggesting therefore that bacteriocins from lactic acid bacteria could be used as agents with antibiotic augmentation capability.     

Effect of photodynamic inactivation of <Emphasis Type="Italic">Escherichia coli</Emphasis> by hypericin

The present study has focused on the effects of hypericin (Hyp) based photodynamic inactivation (PDI) of Escherichia coli (E. coli). To evaluate the efficiency of Hyp based PDI of E. coli, single factor experiments and response surface optimization experiment were conducted to obtain the optimum parameter values (36 µM Hyp, 5.9 J cm^?2 light dose: 16.4 mW cm^?2, 60 W, 260 s, 590 nm and 68 min incubation time) and finally achieved a 4.1 log CFU mL^?1 decrease of E. coli. Cell-Hyp interaction and intracellular reactive oxygen species (ROS) level were detected by fluorescence spectrometric photometer. Data indicated that Hyp possessed a strong ability to bind with cells. In addition, a significant increase was observed in intracellular ROS level after Hyp-based photosensitization treatment. Therefore, Hyp-based photosensitization seems to be a promising method to efficiently inactivate E. coli. It is expected to be a safe, efficient, low cost and practical method which can be applied in the field of food safety.     

Biochemical Properties and Mechanism of Action of Enterocin LD3 Purified from <Emphasis Type="Italic">Enterococcus hirae</Emphasis> LD3

Enterocin LD3 was purified using activity-guided multistep chromatography techniques such as cation-exchange and gel-filtration chromatography. The preparation’s purity was tested using reverse-phase ultra-performance liquid chromatography. The specific activity was tested to be 187.5 AU µg^?1 with 13-fold purification. Purified enterocin LD3 was heat stable up to 121 °C (at 15 psi pressure) and pH 2–6. The activity was lost in the presence of papain, reduced by proteinase K, pepsin and trypsin, but was unaffected by amylase and lipase, suggesting proteinaceous nature of the compound and no role of carbohydrate and lipid moieties in the activity. MALDI-TOF/MS analysis of purified enterocin LD3 resolved m/z 4114.6, and N-terminal amino acid sequence was found to be H₂NQGGQANQ–COOH suggesting a new bacteriocin. Dissipation of membrane potential, loss of internal ATP and bactericidal effect were recorded when indicator strain Micrococcus luteus was treated with enterocin LD3. It inhibited Gram-positive and Gram-negative bacteria including human pathogens such as Staphylococcus aureus, Pseudomonas fluorescens, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri, Listeria monocytogenes, Escherichia coli O157:H7, E. coli (urogenic, a clinical isolate) and Vibrio sp. These properties of purified enterocin LD3 suggest its applications as a food biopreservative and as an alternative to clinical antibiotics.     

Improving methionine and ATP availability by <Emphasis Type="Italic">MET6</Emphasis> and <Emphasis Type="Italic">SAM2</Emphasis> co-expression combined with sodium citrate feeding enhanced SAM accumulation in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

S-adenosyl-l-methionine (SAM), biosynthesized from methionine and ATP, exhibited diverse pharmaceutical applications. To enhance SAM accumulation in S. cerevisiae CGMCC 2842 (wild type), improvement of methionine and ATP availability through MET6 and SAM2 co-expression combined with sodium citrate feeding was investigated here. Feeding 6 g/L methionine at 12 h into medium was found to increase SAM accumulation by 38 % in wild type strain. Based on this result, MET6, encoding methionine synthase, was overexpressed, which caused a 59 % increase of SAM. To redirect intracellular methionine into SAM, MET6 and SAM2 (encoding methionine adenosyltransferase) were co-expressed to obtain the recombinant strain YGSPM in which the SAM accumulation was 2.34-fold of wild type strain. The data obtained showed that co-expression of MET6 and SAM2 improved intracellular methionine availability and redirected the methionine to SAM biosynthesis. To elevate intracellular ATP levels, 6 g/L sodium citrate, used as an auxiliary energy substrate, was fed into the batch fermentation medium, and an additional 19 % increase of SAM was observed after sodium citrate addition. Meanwhile, it was found that addition of sodium citrate improved the isocitrate dehydrogenase activity which was associated with the intracellular ATP levels. The results demonstrated that addition of sodium citrate improved intracellular ATP levels which promoted conversion of methionine into SAM. This study presented a feasible approach with considerable potential for developing highly SAM-productive strains based on improving methionine and ATP availability.     

Structural relationships between genetically closely related O-antigens of <Emphasis Type="Italic">Escherichia coli</Emphasis> and <Emphasis Type="Italic">Shigella</Emphasis> spp.

Gene clusters for biosynthesis of 24 of 34 basic O-antigen forms of Shigella spp. are identical or similar to those of the genetically closely related bacterium Escherichia coli. For 18 of these relatedness was confirmed chemically by elucidation of the O-antigen (O-polysaccharide) structures. In this work, structures of the six remaining O-antigens of E. coli O32, O53, O79, O105, O183 (all related to S. boydii serotypes), and O38 (related to S. dysenteriae type 8) were established using ¹H and ¹³C NMR spectroscopy. They were found to be identical to the Shigella counterparts, except for the O32- and O38-polysaccharides, which differ in the presence of O-acetyl groups. The structure of the E. coli O105-related O-polysaccharide of S. boydii type 11 proposed earlier is revised. The contents of the O-antigen gene clusters of the related strains of E. coli and Shigella spp. and different mechanisms of O-antigen diversification in these bacteria are discussed in view of the O-polysaccharide structures established. These data illustrate the value of the O-antigen chemistry and genetics for elucidation of evolutionary relationships of bacteria.     

Adaptation of <Emphasis Type="Italic">Mycoplasma gallisepticum</Emphasis> to unfavorable growth conditions: Changes in morphological and physiological characteristics

Adaptation of Mycoplasma gallisepticum to unfavorable growth conditions results in altered morphological and physiological characteristics of the cells. M. gallisepticum populations in a complete nutrient medium contain pear-shaped vegetative cells ( d ～ 0.3 μm; l ～ 0.8 μm) with pronounced polar and cytoskeletonlike structures. Such mycoplasma cells are able to induce damage in a bacterial genome, causing an SOS response of the test strain (Escherichia coli PQ37). In a starvation medium, M. gallisepticum produces nanoforms, small coccoid cells (d ～ 0.15–0.2 μm) without either polar or cytoskeleton-like structures. Unlike vegetative cells, nanoforms do not induce genome damage. Alleviation of unfavorable growth conditions results in a reversion of nanoforms to vegetative cells.     

Biosynthesis of di-rhamnolipids and variations of congeners composition in genetically-engineered <Emphasis Type="Italic">Escherichia coli</Emphasis>

Objectives

To engineer Escherichia coli for the heterologous production of di-rhamnolipids, which are important biosurfactants but mainly produced by opportunistic pathogen Pseudomonas aeruginosa.

Results

The codon-optimized rhlAB and rhlC genes originating from P. aeruginosa and Burkholderia pseudomallei were combinatorially expressed in E. coli to produce di-rhamnolipids with varied congeners compositions. Genes involved in endogenous upstream pathways (rhamnose and fatty acids synthesis) were co-overexpressed with rhlAB–rhlC, resulting in variations of rhamnolipids production and congeners compositions. Under the shake-flask condition, co-overexpression of rfbD with rhlAB–rhlC increased rhamnolipids production (0.64 ± 0.02 g l^?1) than that in strain only expressing rhlAB–rhlC (0.446 ± 0.009 g l^?1), which was mainly composed of di-rhamnolipids congeners Rha–Rha–C₁₀–C₁₀.

Conclusion

Biosynthesis of di-rhamnolipids and variations of congeners composition in genetically engineered E. coli strains were achieved via combiniations of mono-/di-rhamnolipids synthesis modules and endogenous upstream modules.

     

Gene <Emphasis Type="Italic">yddG</Emphasis> of <Emphasis Type="Italic">Escherichia coli</Emphasis> encoding the putative exporter of aromatic amino acids: Constitutive transcription and dependence of the expression on the cell growth rate

Gene yddG of Escherichia coli encodes a protein of the inner membrane. Data obtained earlier demonstrated that under conditions of aromatic amino acids overproduction YddG promotes their export from E. coli cells. In this work, a method of primer extension was used to localize the P _yddG promoter, which corresponds to E. coli promoters recognized by RNA polymerase in complex with σ⁷⁰ or σ^S subunits. By constructing a gene of the hybrid protein YddG’-LacZ at the intrinsic site of gene yddG location in the E. coli chromosome and analyzing the activity of β-galactosidase in cells growing on laboratory media LB and M9, the constitutive type of yddG expression at a low level was demonstrated (the activity was about 3 to 4% of the LacZ level under induction of the lac operon in E. coli wild-type cells). The expression of yddG had a twofold increase under conditions of retarded cell growth upon the stress caused by the high NaCl content (0.6 M) or by the presence of phenylalanine excess quantities (>1 mM) in the culture medium.     

Conjugative chromosomal gene transfer in <Emphasis Type="Italic">Bacillus subtilis</Emphasis>

Conjugative transfer of 20-kb chromosomal fragment carrying genes encoding tetracycline (tet ^r ) and lincomycin (lin ^r ) resistance in the soil strain Bacillus subtilis 19 is described. Transfer was preceded by this fragment insertion into the large conjugative p19cat plasmid producing a hybrid plasmid. Insertion frequency was 10^?4?10^?5. Then genes tet ^r and lin ^r were transferred to the recipient strains. The transfer of chromosomal genes inserted into the plasmid and plasmid gene cat occurred sequentially and resembled sexduction, which represents chromosomal gene transfer by F′ and R′ plasmids during conjugation in Escherichia coli and other gram negative bacteria.     

The Effects of Low Doses of Gamma-Radiation on Growth and Membrane Activity of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> GRP3 and <Emphasis Type="Italic">Escherichia coli</Emphasis> M17

Microorganisms are part of the natural environments and reflect the effects of different physical factors of surrounding environment, such as gamma (γ) radiation. This work was devoted to the study of the influence of low doses of γ radiation with the intensity of 2.56?μW (m²?s)^?1 (absorbed doses were 3.8 mGy for the radiation of 15?min and 7.2 mGy—for 30?min) on Escherichia coli M-17 and Pseudomonas aeruginosa GRP3 wild type cells. The changes of bacterial, growth, survival, morphology, and membrane activity had been studied after γ irradiation. Verified microbiological (specific growth rate, lag phase duration, colony-forming units (CFU) number, and light microscopy digital image analysis), biochemical (ATPase activity of bacterial membrane vesicles), and biophysical (H⁺ fluxes throughout cytoplasmic membrane of bacteria) methods were used for assessment of radiation implications on bacteria. It was shown that growth specific rate, lag phase duration and CFU number of these bacteria were lowered after irradiation, and average cell surface area was decreased too. Moreover ion fluxes of bacteria were changed: for P. aeruginosa they were decreased and for E. coli—increased. The N,N′-dicyclohexylcarbodiimide (DCCD) sensitive fluxes were also changed which were indicative for the membrane-associated F₀F₁-ATPase enzyme. ATPase activity of irradiated membrane vesicles was decreased for P. aeruginosa and stimulated for E. coli. Furthermore, DCCD sensitive ATPase activity was also changed. The results obtained suggest that these bacteria especially, P. aeruginosa are sensitive to γ radiation and might be used for developing new monitoring methods for estimating environmental changes after γ irradiation.     

Changes of cationic transport in <Emphasis Type="Italic">AtCAX5</Emphasis> transformant yeast by electromagnetic field environments

The electromagnetic field (EMF) is newly considered as an exogenous environmental stimulus that is closely related to ion transportation on the cellular membrane, maintaining the internal ionic homeostasis. Cation transports of Ca²⁺ and other metal ions, Cd²⁺, Zn²⁺, and Mn²⁺were studied in terms of the external Ca²⁺ stress, [Ca²⁺]_ext, and exposure to the physical EMF. A specific yeast strain K667 was used for controlling CAX5 (cation/H⁺ exchanger) expression. Culture samples were exposed to 60 Hz, 0.1 mT sinusoidal or square magnetics waves, and intracellular cations of each sample were measured and analyzed. AtCAX5 transformant yeast grew normally under the metallic stress. However, the growth of the control group was significantly inhibited under the same cation concentration; 60 Hz and 0.1 mT magnetic field enhanced intracellular cation concentrations significantly as exposure time increased both in the AtCAX5 transformed yeast and in the control group. However, the AtCAX5-transformed yeast showed higher concentration of the intracellular cations than the control group under the same exposure EMF. AtCAX5-transformed yeasts displayed an increment in [Ca²⁺]_int, [K⁺]_int, [Na⁺]_int, and [Zn²⁺]_int concentration under the presence of both sinusoidal and square-waved EMF stresses compared to the control group, which shows that AtCAX5 expressed in the vacuole play an important role in maintaining the homeostasis of intracellular cations. These findings could be utilized in the cultivation of the crops which were resistant to excessive exogenous ions or in the production of biomass containing a large proportion of ions for nutritional food or in the bioremediation process in metal-polluted environments.