• Journal of Microbiology and Biotechnology
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• v.20 no.5
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• pp.917-924
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• 2010

The practicability of transgenic tobacco engineered to express bacterial native mercuric reductase (MerA), responsible for the transport of $Hg^{2+}$ ions into the cell and their reduction to elemental mercury ($Hg^0$), without any codon modification, for phytoremediation of mercury pollution was evaluated. Transgenic tobacco plants reduce mercury ions to the metallic form; take up metallic mercury through their roots; and evolve the less toxic elemental mercury. Transformed tobacco produced a large amount of merA protein in leaves and showed a relatively higher resistance phenotype to $HgCl_2$ than wild type. Results suggest that the integrated merA gene, encoding mercuric reductase, a key enzyme of the bacterial mer operon, was stably integrated into the tobacco genome and translated to active MerA, which catalyzes the bioconversion of toxic $Hg^{2+}$ to the least toxic elemental $Hg^0$, and suggest that MerA is capable of reducing the $Hg^{2+}$, probably via NADPH as an electron donor. The transgenic tobacco expressing merA volatilized significantly more mercury than wild-type plants. This is first time we are reporting the expression of a bacterial native merA gene via the nuclear genome of Nicotiana tabacum, and enhanced mercury volatilization from tobacco transgenics. The study clearly indicates that transgenic tobacco plants are reasonable candidates for the remediation of mercurycontaminated areas.

• Korean Journal of Microbiology
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• v.28 no.1
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• pp.76-82
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• 1990

In samples taken from mouth of the Nakdong River, mercury-resistant bacteria grown on the media supplemented with over 20 ppm of mercuric chlorice were below 0.3% of all aerobic heterotrophs. Among them, seven strains grown over 100 ppm of mercuric chloride were isolated and all were identified as Pseudomonas. The toxic effect of mercury on the growth of the most resistant strain N14 was influenced by the organic compounds and concentration. The growth and physiological activity to N14 strain were affected by toxic mercury in the early stage: The viable count and glucose turn over rate of N14 strain dropped to the lowest level as soon as the bacteria came into contact with mercury. During the extended lag period, however, bacteria accommodated to the stress and the viable count and glucose turnover rate increased. After the lag period, bacteria began to proliferate and their growth reached similar level to that of control. In crude extracts of N14 strain grown in nutrient browth containing. $10{\mu}M$ $HgCl_{2}$, a mercuric ion dependent oxidation of NADPH was demonstrated. Therefore the mechanism of mercury-resistance of the N14 strain involved the elimination of the mercury from growth media. In the N14 strain which a wide range of resistance to antibiotics was observed in, four multiple plasmids were detected. As a result, the supposition that N14 strain has a plasmid-encoded enzyme system may be quite within the realms of possobility.

• Journal of Microbiology
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• v.44 no.1
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• pp.35-41
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• 2006

The unique gene encoding thioredoxin reductase (TrxR) was previously cloned and characterized from the fission yeast Schizosaccharomyces pombe, and its expression was induced by oxidative stress. To elucidate tbe regulatory mechanism of the S. pombe TrxR gene, three fusion plasmids were generated using polymerase chain reaction: pYUTR20, pYUTR30, and pYUTR40. Plasmid pYUTR20 has an upstream region of 891 base pairs, pYUTR30 has 499 in this region, and pYUTR40 has an 186 bp upstream region. Negatively acting sequence is located between $-1,526\;\~\;-891bp$ upstream of the gene. The upstream sequence, responsible for the induction of TrxR by menadione (MD), is situated on the $-499\;\~\;-186bp$ region, which is also required for TrxR induction by mercuric chloride. The same region also appeared to be required for Pap1-mediated transcriptional regulation of the TrxR gene, which contains the two plausible Papl binding sites, TTACGAAT and TTACGCGA. Consistently, basal and inducible expression of the TrxR gene was markedly lower in the Pap1-negative TP108-3C cells than in wild-type yeast cells. In summary, up-regulation of the S. pombe TrxR gene is mediated by Pap1 via the transcriptional motif(s) located on the $-499\;\~\;-186bp$ region.

• Fisheries and Aquatic Sciences
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• v.15 no.3
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• pp.215-220
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• 2012

The effects of inorganic mercury on hematological parameters and hepatic oxidative stress enzyme activity were studied in olive flounder Paralichthys olivaceus. Fish were injected twice intraperitoneally with mercuric chloride (2, 4, or 8 mg Hg/kg BW). The major hematological findings were significant decreases in the red blood cell count, hematocrit value, and hemoglobin level in olive flounder exposed to 8 mg Hg/kg BW. Remarkably low levels of calcium and chloride, and reduced osmolality, were also observed at 8 mg Hg/kg BW. In hepatic tissue, significant increases in glutathione peroxidase and catalase activity were observed above 4 mg Hg/kg BW Inorganic mercury also increased glutathione S-transferase and glutathione reductase activity at 8 mg Hg/kg BW in hepatic tissue. The present findings suggest that exposure to a low concentration (${\geq}4$ mg Hg/kg BW) of inorganic mercury can cause significant changes in hematological and antioxidant parameters.