Genome-Wide Association Studies for Albuminuria of Nondiabetic Taiwanese Population.

INTRODUCTION: Chronic kidney disease, which is defined by a reduced estimated glomerular filtration rate and albuminuria, imposes a large health burden worldwide. Ethnicity-specific associations are frequently observed in genome-wide association studies (GWAS). This study conducts a GWAS of albuminuria in the nondiabetic population of Taiwan. METHODS: Nondiabetic individuals aged 30-70 years without a history of cancer were enrolled from the Taiwan Biobank. A total of 6,768 subjects were subjected to a spot urine examination. After quality control using PLINK and imputation using SHAPEIT and IMPUTE2, a total of 3,638,350 single-nucleotide polymorphisms (SNPs) remained for testing. SNPs with a minor allele frequency of less than 0.1% were excluded. Linear regression was used to determine the relationship between SNPs and log urine albumin-to-creatinine ratio. RESULTS: Six suggestive loci are identified in or near the FCRL3 (p = 2.56 × 10-6), TMEM161 (p = 4.43 × 10-6), EFCAB1 (p = 2.03 × 10-6), ELMOD1 (p = 2.97 × 10-6), RYR3 (p = 1.34 × 10-6), and PIEZO2 (p = 2.19 × 10-7). Genetic variants in the FCRL3 gene that encode a secretory IgA receptor are found to be associated with IgA nephropathy, which can manifest as proteinuria. The PIEZO2 gene encodes a sensor for mechanical forces in mesangial cells and renin-producing cells. Five SNPs with a p-value between 5 × 10-6 and 5 × 10-5 are also identified in five genes that may have a biological role in the development of albuminuria. CONCLUSION: Five new loci and one known suggestive locus for albuminuria are identified in the nondiabetic Taiwanese population.

Application of PACS system in the standardized residency training of cardiovascular medicine / 中华医学教育探索杂志

Objective:To evaluate the effect of PACS system (picture archiving and communication system) in the standardized residency training of cardiovascular medicine.Methods:Fifty-nine residents taking the standardized residency training of cardiovascular medicine in Changhai Hospital from 2018 to 2019 were randomly divided into PACS teaching group ( n = 30) and traditional teaching group ( n = 29). The research group adopted the PACS system for the teaching of cardiovascular medicine, and the control group took the traditional teaching method. The teaching effect was evaluated by theoretical examination, imaging examination and questionnaire. SPSS 19.0 was used for t test and chi-square test. Results:The theoretical and film reading scores of the PACS teaching group were significantly higher than those of the control group [(87.70 ± 6.52) vs. (80.55 ± 8.63); (86.67 ± 6.33) vs. (77.48 ± 10.29), P < 0.05)]. The results of the questionnaire showed that PACS teaching method was helpful for residents to master cardiovascular knowledge, arouse their learning interest and improve their clinical thinking ability. The satisfaction with the teaching method in the PACS teaching group was significantly higher than that in the traditional teaching group [(9.22 ± 0.44) vs. (8.26 ± 0.72), P < 0.05]. Conclusion:The application of PACS system in the teaching of cardiovascular medicine can significantly improve the teaching effect of residents.

Incidence, clinical characteristics and prognostic factor of patients with COVID-19: a systematic review and meta-analysis

BackgroundRecently, Coronavirus Disease 2019 (COVID-19) outbreak started in Wuhan, China. Although the clinical features of COVID-19 have been reported previously, data regarding the risk factors associated with the clinical outcomes are lacking. ObjectivesTo summary and analyze the clinical characteristics and identify the predictors of disease severity and mortality. MethodsThe PubMed, Web of Science Core Collection, Embase, Cochrane and MedRxiv databases were searched through February 25, 2020. Meta-analysis of Observational Studies in Epidemiology (MOOSE) recommendations were followed. We extracted and pooled data using random-e{square}ects meta-analysis to summary the clinical feature of the confirmed COVID-19 patients, and further identify risk factors for disease severity and death. Heterogeneity was evaluated using the I2 method and explained with subgroup analysis and meta-regression. ResultsA total of 30 studies including 53000 patients with COVID-19 were included in this study, the mean age was 49.8 years (95% CI, 47.5-52.2 yrs) and 55.5% were male. The pooled incidence of severity and mortality were 20.2% (95% CI, 15.1-25.2%) and 3.1% (95% CI, 1.9-4.2%), respectively. The predictor for disease severity included old age ([≥] 50 yrs, odds ratio [OR] = 2.61; 95% CI, 2.29-2.98), male (OR =1.348, 95% CI, 1.195-1.521), smoking (OR =1.734, 95% CI, 1.146-2.626) and any comorbidity (OR = 2.635, 95% CI, 2.098-3.309), especially chronic kidney disease (CKD, OR = 6.017; 95% CI, 2.192-16.514), chronic obstructive pulmonary disease (COPD, OR = 5.323; 95% CI, 2.613-10.847) and cerebrovascular disease (OR = 3.219; 95% CI, 1.486-6.972). In terms of laboratory results, increased lactate dehydrogenase (LDH), C-reactive protein (CRP) and D-dimer and decreased blood platelet and lymphocytes count were highly associated with severe COVID-19 (all for P < 0.001). Meanwhile, old age ([≥] 60 yrs, RR = 9.45; 95% CI, 8.09-11.04), followed by cardiovascular disease (RR = 6.75; 95% CI, 5.40-8.43) hypertension (RR = 4.48; 95% CI, 3.69-5.45) and diabetes (RR = 4.43; 95% CI, 3.49-5.61) were found to be independent prognostic factors for the COVID-19 related death. ConclusionsTo our knowledge, this is the first evidence-based medicine research to explore the risk factors of prognosis in patients with COVID-19, which is helpful to identify early-stage patients with poor prognosis and adapt effective treatment.

Cysteine and histidine residues are involved in Escherichia coli Tn21 MerE methylmercury transport.

Bacterial resistance to mercury compounds (mercurials) is mediated by proteins encoded by mercury resistance (mer) operons. Six merE variants with site-directed mutations were constructed to investigate the roles of the cysteine and histidine residues in MerE protein during mercurial transport. By comparison of mercurial uptake by the cell with intact and/or variant MerE, we showed that the cysteine pair in the first transmembrane domain was critical for the transport of both Hg(II) and CH 3Hg(I). Also, the histidine residue located near to the cysteine pair was critical for Hg(II) transport, whereas the histidine residue located on the periplasmic side was critical for CH 3Hg(I) transport. Thus, enhanced mercurial uptake mediated by MerE may be a promising strategy for the design of new biomass for use in the bioremediation of mercurials in the environment.

A Novel Role of MerC in Methylmercury Transport and Phytoremediation of Methylmercury Contamination.

MerC, encoded by merC in the transposon Tn21 mer operon, is a heavy metal transporter with potential applications for phytoremediation of heavy metals such as mercuric ion and cadmium. In this study, we demonstrate that MerC also acts as a transporter for methylmercury. When MerC was expressed in Escherichia coli XL1-Blue, cells became hypersensitive to CH3Hg(I) and the uptake of CH3Hg(I) by these cells was higher than that by cells of the isogenic strain. Moreover, transgenic Arabidopsis plants expressing bacterial MerC or MerC fused to plant soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) accumulated CH3Hg(I) effectively and their growth was comparable to the wild-type plants. These results demonstrate that when the bacterium-derived merC gene is ectopically introduced in genetically modified plants, MerC expression in the transgenic plants promotes the transport and sequestration of methylmercury. Thus, our results show that the expression of merC in Arabidopsis results in transgenic plants that could be used for the phytoremediation and elimination of toxic methylmercury from the environment.

Cyclophotocoagulation through 23G minimally invasive scleral incision treating refractory glaucoma / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To observe the efficacy and safety of cyclophoto-coagulation through 23G minimally invasive scleral incision in the treatment of refractory glaucoma. <p>METHODS: Totally 23 patients(23 eyes)were taken the surgery-the cyclophotocoagulation-through 23G minimally invasive scleral incision. We observed the changes of intraocular pressure(IOP), the best corrected visual acuity(BCVA), the quantity of drugs reducing intraocular pressure and complications in the pre-and post-operation. <p>RESLUTS: Comparing with preoperative, the postopera-tive IOP, BCVA and the number of IOP-decreased drugs were statistically significant(<i>P</i><0.05); the complication was fewer. <p>CONCLUSION: The 23G minimally invasive scleral incision cyclophotocoagulation is a new type of safe and effective surgical method for the treatment of refractory glaucoma.

TAK1-binding proteins (TAB1 and TAB2) in grass carp (Ctenopharyngodon idella): identification, characterization, and expression analysis after infection with Ichthyophthirius multifiliis.

Transforming growth factor-ß activated kinase-1 (TAK1) is a key regulatory molecule in toll-like receptor (TLR), interleukin-1 (IL-1), and tumor necrosis factor (TNF) signaling pathways. The activation of TAK1 is specifically regulated by two TAK1-binding proteins, TAB1 and TAB2. However, the roles of TAB1 and TAB2 in fish have not been reported to date. In the present study, TAB1 (CiTAB1) and TAB2 (CiTAB2) in grass carp (Ctenopharyngodon idella) were identified and characterized, and their expression profiles were analyzed after fish were infected with the pathogenic ciliate Ichthyophthirius multifiliis. The full-length CiTAB1 cDNA is 1949 bp long with an open reading frame (ORF) of 1497 bp that encodes a putative protein of 498 amino acids containing a typical PP2Cc domain. The full-length CiTAB2 cDNA is 2967 bp long and contains an ORF of 2178 bp encoding a putative protein of 725 amino acids. Protein structure analysis revealed that CiTAB2 consists of three main structural domains: an N-terminal CUE domain, a coiled-coil domain, and a C-terminal ZnF domain. Multiple sequence alignment showed that CiTAB1 and CiTAB2 share high sequence identity with other known TAB1 and TAB2 proteins, and several conserved phosphorylation sites and an O-GlcNAc site were deduced in CiTAB1. Phylogenetic tree analysis demonstrated that CiTAB1 and CiTAB2 have the closest evolutionary relationship with TAB1 and TAB2 of Danio rerio, respectively. CiTAB1 and CiTAB2 were both widely expressed in all examined tissues with the highest levels in the heart and liver, respectively. After infection with I. multifiliis, the expressions of CiTAB1 and CiTAB2 were both significantly up-regulated in all tested tissues at most time points, which indicates that these proteins may be involved in the host immune response against I. multifiliis infection.

Increase methylmercury accumulation in Arabidopsis thaliana expressing bacterial broad-spectrum mercury transporter MerE.

The bacterial merE gene derived from the Tn21 mer operon encodes a broad-spectrum mercury transporter that governs the transport of methylmercury and mercuric ions across bacterial cytoplasmic membranes, and this gene is a potential molecular tool for improving the efficiency of methylmercury phytoremediation. A transgenic Arabidopsis engineered to express MerE was constructed and the impact of expression of MerE on methylmercury accumulation was evaluated. The subcellular localization of transiently expressed GFP-tagged MerE was examined in Arabidopsis suspension-cultured cells. The GFP-MerE was found to localize to the plasma membrane and cytosol. The transgenic Arabidopsis expressing MerE accumulated significantly more methymercury and mercuric ions into plants than the wild-type Arabidopsis did. The transgenic plants expressing MerE was significantly more resistant to mercuric ions, but only showed more resistant to methylmercury compared with the wild type Arabidopsis. These results demonstrated that expression of the bacterial mercury transporter MerE promoted the transport and accumulation of methylmercury in transgenic Arabidopsis, which may be a useful method for improving plants to facilitate the phytoremediation of methylmercury pollution.

Role of MerC, MerE, MerF, MerT, and/or MerP in resistance to mercurials and the transport of mercurials in Escherichia coli.

The characteristics of bacteria take up mercury into cells via membrane potential-dependent sequence-divergent 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 C6H5Hg(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 C6H5Hg(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.

Mercurial-resistance determinants in Pseudomonas strain K-62 plasmid pMR68.

We report the complete nucleotide sequence of plasmid pMR68, isolated from Pseudomonas strain K-62, two plasmids contribute to broad-spectrum mercury resistance and that the mer operon from one of them (pMR26) has been previously characterized. The plasmid was 71,020 bp in length and contained 75 coding regions. Three mer gene clusters were identified. The first comprised merR-orf4-orf5-merT1-merP1-merF-merA-merB1, which confers bacterial resistance to mercuric ions and organomercury. The second and third clusters comprised merT2-merP2, which encodes a mercury transport system, and merB2, which encodes an organomercurial lyase, respectively. The deduced amino acid sequences for the proteins encoded by each of the mer genes identified in pMR68 bore greater similarity to sequences from Methylobacterium extorquens AM1 than to those from pMR26, a second mercury-resistance plasmid from Pseudomonas strain K-62. Escherichia coli cells carrying pMKY12 (containing merR-orf4-orf5-merT1-merP1-merF-merA-merB1 cloned from pMR68) and cells carrying pMRA114 (containing merR-merT-merP-merA-merG-merB1 cloned from plasmid pMR26) were more resistant to, and volatilized more, mercury from mercuric ions and phenylmercury than the control cells. The present results, together with our earlier findings, indicate that the high phenylmercury resistance noted for Pseudomonas strain K-62 seems to be achieved by multiple genes, particularly by the multiple merB encoding organomercurial lyase and one merG encoding cellular permeability to phenylmercury. The novel mer gene identified in pMR68 may help us to design new strategies aimed at the bioremediation of mercurials.

Expression profiles of toll-like receptors in channel catfish (Ictalurus punctatus) after infection with Ichthyophthirius multifiliis.

Toll-like receptors (TLRs) play a crucial role in the innate immune system, but to date the roles of fish TLRs in response to parasitic infection are still poorly understood. In the present study, we used channel catfish (Ictalurus punctatus) and the ciliate parasite Ichthyophthirius multifiliis as a model to investigate whether and which fish TLRs play important roles in the immune response against parasitic pathogens by detecting the expression profiles of a complete set of TLRs in catfish at different time points after infection with I. multifiliis. The expression profiles of TLR1 and TLR2 were similar, and both were significantly up-regulated in the skin and head kidney at most time points after infection. Furthermore, the expression of TLR2 was also up-regulated in the gill and spleen. TLR9 was induced in the skin and gill, whereas TLR21 was induced in the head kidney and spleen after infection. For TLR19, significant up-regulation was observed in the skin and gill, but significant down-regulation was detected in the head kidney and spleen. In contrast to TLR19, TLR25 was significantly up-regulated in the head kidney and spleen at some time points. No significant changes were observed for the rest of the TLRs at most time points. The results indicated that some TLRs may play essential roles in catfish defense against I. multifiliis infection.

Grass carp (Ctenopharyngodon idella) TRAF6 and TAK1: molecular cloning and expression analysis after Ichthyophthirius multifiliis infection.

Ichthyophthirius multifiliis, a pathogenic ciliate parasite, infects almost all freshwater fish species and causes significant economic losses. Tumor necrosis factor receptor-associated factor 6 (TRAF6) and transforming growth factor-ß-activated kinase 1 (TAK1) are two important signaling molecules involved in toll-like receptor (TLR) signal transduction. To date, the roles of TRAF6 and TAK1 in host defense against fish parasites are still poorly understood. In the present study, TRAF6 (CiTRAF6) and TAK1 (CiTAK1) were identified from grass carp (Ctenopharyngodon idella). The full-length cDNA sequence of CiTRAF6 (2250 bp) includes an open reading frame (ORF) of 1629 bp, which shows a high similarity to that of Cyprinus carpio TRAF6 and encodes a putative protein of 542 amino acids containing one RING domain, two zinc fingers, one coiled-coil region, and one MATH domain. The full-length CiTAK1 cDNA sequence is 2768 bp and includes an ORF of 1626 bp that encodes a putative protein of 541 amino acids containing a conserved serine/threonine protein kinase catalytic domain and a coiled-coil region. Phylogenetic analysis showed that CiTRAF6 and CiTAK1 were clustered with TRAF6 and TAK1 of other teleosts, respectively. CiTRAF6 and CiTAK1 were both constitutively expressed in all examined tissues but with varied expression levels. The highest expressions of CiTRAF6 and CiTAK1 were in the head kidney and spleen, respectively. The expression profiles of CiTRAF6 and CiTAK1 were detected in grass carp after I. multifiliis infection. Expressions of both genes were significantly up-regulated in the skin, gill, head kidney, and spleen at most time points after infection, indicating that CiTRAF6 and CiTAK1 may play essential roles in grass carp defense against I. multifiliis.

Expression of the bacterial heavy metal transporter MerC fused with a plant SNARE, SYP121, in Arabidopsis thaliana increases cadmium accumulation and tolerance.

The bacterial merC gene from the Tn21-encoded mer operon is a potential molecular tool for improving the efficiency of metal phytoremediation. Arabidopsis SNARE molecules, including SYP111, SYP121, and AtVAM3 (SYP22), were attached to the C-terminus of MerC to target the protein to various organelles. The subcellular localization of transiently expressed GFP-fused MerC-SYP111, MerC-SYP121, and MerC-AtVAM3 was examined in Arabidopsis suspension-cultured cells. We found that GFP-MerC-SYP111 and GFP-MerC-SYP121 localized to the plasma membrane, whereas GFP-AtVAM3 localized to the vacuolar membranes. These results demonstrate that SYP111/SYP121 and AtVAM3 target foreign molecules to the plasma membrane and vacuolar membrane, respectively. To enhance the efficiency and potential of plants to sequester and accumulate cadmium from contaminated sites, transgenic Arabidopsis plants expressing MerC, MerC-SYP111, MerC-SYP121, or MerC-AtVAM3 were generated. The transgenic plants that expressed MerC, MerC-SYP121, or MerC-AtVAM3 appeared to be normal, whereas the transgenic that expressed MerC-SYP111 exhibited severe growth defects. The transgenic plants expressing merC-SYP121 were more resistant to cadmium than the wild type and accumulated significantly more cadmium. Thus, the expression of MerC-SYP121 in the plant plasma membrane may provide an ecologically compatible approach for the phytoremediation of cadmium pollution.

[Application of mercury-resistant genes in bioremediation of mercurials in environments].

Mercury and its organic compounds, especially methylmercury are extremely hazardous pollutants that have been released into the environment in substantial quantities by natural events and anthropogenic activities. Due to the acute toxicity of these contaminants, there is an urgent need to develop an effective and affordable technology to remove them from the environments. Recently, attempts have been made to utilize bacterial mer operon-mediated reduction and volatilization of mercurials for environmental remediation of mercury pollution. However, application of this technology to the treatment of mercury-contaminated environments has been limited by social concerns about the release of volatile mercury that will become part of the local mercury cycle and repollute the environment again, into the ambient air. To improve this environmental problem, a new mercury scavenging mechanism that could be expressed in living cells and accumulates mercury from contaminated site without releasing mercury vapor is necessitated. To construct a new biocatalyst that is capable of specifically accumulating mercury from contaminated sites without releasing mercury vapor, we have genetically engineered bacteria and tobacco plant for removal of mercury from wastewater and soils, respectively, to express a mercury transport system and organomercurial lyase enzyme simultaneously, and overexpress polyphosphate, a chelator of divalent metals. The applicability of these new engineered biocatalysts in the environmental remediation of mercurials is evaluated and discussed in this review.

Development of a transgenic tobacco plant for phytoremediation of methylmercury pollution.

To develop the potential of plant for phytoremediation of methylmercury pollution, a genetically engineered tobacco plant that coexpresses organomercurial lyase (MerB) with the ppk-specified polyphosphate (polyP) and merT-encoding mercury transporter was constructed by integrating a bacterial merB gene into ppk/merT-transgenic tobacco. A large number of independent transgenic tobaccos was obtained, in some of which the merB gene was stably integrated in the plant genome and substantially translated to the expected MerB enzyme in the transgenic tobacco. The ppk/merT/merB-transgenic tobacco callus showed more resistance to methylmercury (CH3Hg+) and accumulated more mercury from CH3Hg+-containing medium than the ppk/merT-transgenic and wild-type progenitors. These results suggest that the MerB enzyme encoded by merB degraded the incorporated CH3Hg+ to Hg2+, which then accumulated as a less toxic Hg-polyP complex in the tobacco cells. Phytoremediation of CH3Hg+ and Hg2+ in the environment with this engineered ppk/merT/merB-transgenic plant, which prevents the release mercury vapor (Hg0) into the atmosphere in addition to generating potentially recyclable mercury-rich plant residues, is believed to be more acceptable to the public than other competing technologies, including phytovolatilization.

Development of a luminescence-based biosensor for detection of methylmercury.

A recombinant whole-cell bacterial sensor for highly selective and sensitive detection of the bioavailable methylmercury in the environment was constructed. The biosensor carries luciferase gene, luxAB, from Vibrio harveyi as a reporter under the control of the mercury inducible regulatory part of mer-operon from Pseudomonas K-62 plasmid pMR26. In addition, a merB gene encoding organomercurial lyase which cleaves the C-Hg bond of methylmercury to give Hg(2+ )was coexpressed in the sensor. The resulting bacterial sensor responded specifically to methylmercury, and the lowest detectable concentration of methylmercury was 10 pM with 1 ml sample in the optimized assay conditions. This detection limit is enough to detect this compound in many contaminated and some pristine environmental samples.

Engineering expression of the heavy metal transporter MerC in Saccharomyces cerevisiae for increased cadmium accumulation.

The merC gene from the Tn21-encoded mer operon has potential uses as a molecular tool for bioremediation. It was overexpressed as the fusion proteins MerC-Sso1p or MerC-Vam3p in Saccharomyces cerevisiae. Green fluorescent protein (GFP)-MerC-Sso1p fusion proteins located primarily in the plasma membrane, although some protein was detected in the endoplasmic reticulum. In contrast, GFP-MerC-Vam3p was expressed in the vacuolar membranes. These results suggest that yeast Sso1p and Vam3p are essential for targeting molecules to the plasma and vacuolar membranes, respectively. Significantly more cadmium ions were accumulated by yeast cells expressing MerC-Sso1p than with MerC-Vam3p or control cells. These results suggest that expression of MerC in the plasma membrane may be a particularly promising strategy for improving accumulation of cadmium in yeast.

Genetic engineering of transgenic tobacco for enhanced uptake and bioaccumulation of mercury.

To further enhance the efficiency and potential of plants for phytoremediation of mercury pollution, a genetically engineered tobacco to simultaneously express mercury transporter, mercury transporter (MerT) and mercury chelator, polyphosphate (polyP) was constructed by integrating bacterial merT gene in polyphosphate kinase gene (ppk)-transgenic tobacco, and its ability to phytoremediate mercury was evaluated. Integration of merT gene into ppk-transgenic tobacco did not significantly affect the mercury resistant phenotypes and polyP production. Transgenic expression of MerT in ppk-transgenic tobacco resulted in accelerated and enhanced mercury uptake into tobacco. In addition, tobacco expressing MerT and polyP accumulated significantly more mercury than the ppk-transgenic tobacco from medium containing a wide range of low concentrations of Hg(2+). The combination of accelerated mercury uptake and enhanced mercury accumulation mediated by MerT represents one way for shortening the purification completion time, and for improving tobacco plants to be more suitable for use in phytoremediation of low levels of mercury contamination.

The MerE protein encoded by transposon Tn21 is a broad mercury transporter in Escherichia coli.

In order to clarify the physiological role of the merE gene of transposon Tn21, a pE4 plasmid that contained the merR gene of plasmid pMR26 from Pseudomonas strain K-62, and the merE gene of Tn21 from the Shigella flexneri plasmid NR1 (R100) was constructed. Bacteria with plasmid pE4 (merR-o/p-merE) were more hypersensitive to CH(3)Hg(I) and Hg(II), and took up significantly more CH(3)Hg(I) and Hg(II), than the isogenic strain. The MerE protein encoded by pE4 was localized in the membrane cell fraction, but not in the soluble fraction. Based on these experimental results, we suggest for the first time that the merE gene is a broad mercury transporter mediating the transport of both CH(3)Hg(I) and Hg(II) across the bacterial membrane.

Engineering expression of polyphosphate confers cadmium resistance in tobacco.

The feasibility of transgenic tobacco, genetically engineered to express bacterial polyphosphate (polyP) for phytoremediation of cadmium pollution was examined. The transgenic tobacco showed more resistance to Cd2+ and accumulated more Cd2+ than its wild-type progenitors. These results suggest that polyP has abilities to reduce Cd2+ toxicity, probably via a chelation mechanism, and to accumulate cadmium in the transgenic tobacco. Based on the results obtained in this study, polyP-mediated Cd2+ accumulation may serve as a useful strategy for Cd2+ phytoremediation.