Removal of inorganic and organic mercurials by immobilized bacteria having mer-ppk fusion plasmids

Kiyono, Masako; Omura, H.; Omura, Tomoko; Murata, Soichiro; Pan-Hou, Hidemitsu

doi:10.1007/s00253-003-1282-y

Cited by 29 publications

(19 citation statements)

References 26 publications

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“…[9][10][11] In theory, plants engineering expression of polyP would also reduce mercury toxicity and accumulate more mercury from the polluted sites. As expected, we found that tobacco plant genetically engineered to express bacterial polyP was more resistant to Hg 2ϩ than its wild-type progenitors.…”

mentioning

confidence: 99%

Accumulation of Mercury in Transgenic Tobacco Expressing Bacterial Polyphosphate

Nagata

Ishikawa

Kiyono

et al. 2006

Biological & Pharmaceutical Bulletin

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Mercury pollution is a worldwide problem in environments, resulting primarily from its industrial use in bleaching operations, as a catalyst, as a pigment in paints, and in the mining of gold. The effects of this heavy metal on the ecosystem and human health are growing concerns. Decontamination of mercury in the sediment and soil around industrial plants has been a challenge for a long time. Unfortunately, numerous sites contaminated with mercurials have not been remediated because of the high costs of dredging and landfilling.2) Phytoremediation, using plants to extract and/or sequester mercurials, is often regarded as a relatively inexpensive and efficient way of cleaning up the mercury-contaminated sites.Recently, with advances in biotechnology, phytoremediation utilizing specific plants to remove mercurials from contaminated sites has become one of the most rapidly developing fields for environmental restoration. Several studies have successfully integrated bacterial mer-genes into plant genome to create superior plants for phytoremediation of mercurial contaminated sites, based on the merA-mediated mercury reduction and volatilization mechanism.3-8) However, phytovolatilization of mercurials mediated by bacterial merA gene from the polluted sites would still cause public anxiety because of the release of mercury vapor into the ambient air that will redistribute in the ecosphere and be recycled to environment. To help solve this environmental problem, a new mercury-scavenging mechanism that can be expressed in plant cells and accumulate mercury from contaminated sites without releasing mercury vapor into the ambient air is required in place of the merA-mediated mercury reduction mechanism.In the previous papers, we reported that expression of ppkspecified polyphosphate (polyP) in a genetically engineered Escherichia coli strain resulted in significantly increased the bioaccumulation of Hg 2ϩ from simulated and actual wastewaters, and protected the bacterial cells from the toxic accumulated Hg 2ϩ . [9][10][11] In theory, plants engineering expression of polyP would also reduce mercury toxicity and accumulate more mercury from the polluted sites. As expected, we found that tobacco plant genetically engineered to express bacterial polyP was more resistant to Hg 2ϩ than its wild-type progenitors.12) The transported Hg 2ϩ seemed to be converted to a less toxic molecule, probably via chelation formation with ppk-specific polyP in the tobacco tissues just as the fact previously described in a bacterial system. 9,10) From these results we communicated that expression of ppk-specific polyP in transgenic tobacco may provide an ecologically compatible approach for environmental phytoremediation of mercury pollution in soils. However, the feasibility of ppk-specific polyP for phytoremediation of mercury had not uncovered. In this study, the ability of ppk-transgenic tobacco to accumulate mercury from the contaminated sites was investigated and the feasibility of this engineered tobacco for environmental remediation of ...

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mentioning

confidence: 99%

Accumulation of Mercury in Transgenic Tobacco Expressing Bacterial Polyphosphate

Nagata

Ishikawa

Kiyono

et al. 2006

Biological & Pharmaceutical Bulletin

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“…We have previously shown that polyphosphate, a biomolecule is capable of reducing the cytotoxicity of the transported Hg(II) and retaining more mercury in the living cells but without the cells via chelation formation with polyphosphate. [27][28][29] In conclusion, this study showed for the first time that in addition to MerE and MerT, MerF and MerC are broadspectrum mercury transporters that mediate the transport of mercuric ions and phenylmercury. Thus, in addition, MerC is the most efficient tool for designing a potential bioreactor used in environmental bioaccumulation of mercurial pollution.…”

Section: Discussionmentioning

confidence: 99%

Role of MerC, MerE, MerF, MerT, and/or MerP in Resistance to Mercurials and the Transport of Mercurials in <i>Escherichia coli</i>

Sone

Nakamura

Pan-Hou

et al. 2013

Biological & Pharmaceutical Bulletin

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The characteristics of bacteria take up mercury into cells via membrane potential-dependent sequencedivergent members of the mercuric ion (Mer) superfamily, i.e., a periplasmic mercuric ion scavenging protein (MerP) and one or more inner membrane-spanning proteins (MerC, MerE, MerF, and MerT), which transport mercuric ions into the cytoplasm, have been applied in engineering of bioreactor used for mercurial bioremediation. We engineered bacteria to express MerC, MerE, MerF, or MerT with or without MerP to clarify their individual role and potential in transport of mercurial. By immunoblot analysis using specific polyclonal antibody, the proteins encoded by merC, merE, merF, merT or merP, were certainly expressed and identified in the membrane fraction. Bacteria expressing MerC, MerE, MerF or MerT in the absence of MerP transported significantly more C 6 H 5 Hg(I) and Hg(II) across bacterial membrane than their isogenic strain. In vivo expression of MerP in the presence of all the transporters did not cause apparent difference to the C 6 H 5 Hg(I) transport, but gives an apparently higher Hg(II) transport than that did by MerE, MerF or MerT but not by MerC. Among the four transporters studied, MerC showed more potential to transport Hg(II) across bacterial membrane than MerE, MerF and MerT. Together these findings, we demonstrated for the first time that in addition to MerE and MerT, MerF and MerC are broad-spectrum mercury transporters that mediate both Hg(II) and phenylmercury transport into cells. Our results suggested that MerC is the most efficient tool for designing mercurial bioremediation systems, because MerC is sufficient for mercurial transport into cells.

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“…[26][27][28] The additional mer gene, merG, located between merA and merB1 on pMRA17, is 654 bp long, encoding a 217-amino acid polypeptide. 29) The predicted amino acid sequence of the gene product (MerG) has a good leader sequence that contains a short, positively charged region at N-terminus, followed by a hydrophobic region and a signal peptide cleavage site (alanine-leucine-alanine-alanine, ALAA) at position [32][33][34][35]. This characteristic N-terminal sequence is homologous to the "leader sequences" of known periplasmic proteins.…”

Section: Function Of Pseudomonas K-62 Mer Genesmentioning

confidence: 99%

“…The immobilized cells engineered to express the mercury transport system, organomercurial lyase, and polyphosphate efficiently removed both organic and inorganic mercury from contaminated wastewater over a wide concentration range of mercurials, probably via intracellular accumulation mediated by ppk-specified polyphosphate. 35) Almost all of the mercurials that disappeared in the wastewater had accumulated in the alginate beads. The Hg 2+ and C 6 H 5 Hg + coexisting in the medium were also simultaneously and efficiently removed by the immobilized cells carrying pMKB18.…”

Section: Genetically Engineered Bacteria For Mercury Remediationmentioning

confidence: 99%

“…Our results showed that the immobilized cells carrying pMKB18 are able to remove mercurials repeatedly from mercurial-contaminated wastewater without significant loss of their activities. 35) In addition, the high resistance to other ambient metals or a wide range of pH may make it feasible to remove mercury selectively from sites contaminated with various metals. From these results, it is concluded that the immobilized bacterium carrying pMKB18 is useful for simultaneous removal of both inorganic and organic mercurials from contaminated wastewater (Fig.…”

Section: Genetically Engineered Bacteria For Mercury Remediationmentioning

confidence: 99%

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Genetic Engineering of Bacteria for Environmental Remediation of Mercury

Kiyono

Pan-Hou

2006

JOURNAL OF HEALTH SCIENCE

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Removal of inorganic and organic mercurials by immobilized bacteria having mer-ppk fusion plasmids

Cited by 29 publications

References 26 publications

Accumulation of Mercury in Transgenic Tobacco Expressing Bacterial Polyphosphate

Accumulation of Mercury in Transgenic Tobacco Expressing Bacterial Polyphosphate

Role of MerC, MerE, MerF, MerT, and/or MerP in Resistance to Mercurials and the Transport of Mercurials in <i>Escherichia coli</i>

Genetic Engineering of Bacteria for Environmental Remediation of Mercury

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