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Journal ArticleDOI

Mercury Resistance in a Plasmid-Bearing Strain of Escherichia coli

01 Dec 1972-Journal of Bacteriology (American Society for Microbiology)-Vol. 112, Iss: 3, pp 1228-1236
TL;DR: A strain of Escherichia coli carrying genes determining mercury resistance on a naturally occurring resistance transfer factor (RTF) converts 95% of 10(-5)m Hg(2+) (chloride) to metallic mercury at a rate of 4 to 5 nmoles of Hg (2+) per min per 10(8) cells.
Abstract: A strain of Escherichia coli carrying genes determining mercury resistance on a naturally occurring resistance transfer factor (RTF) converts 95% of 10−5m Hg2+ (chloride) to metallic mercury at a rate of 4 to 5 nmoles of Hg2+ per min per 108 cells. The metallic mercury is rapidly eliminated from the culture medium as mercury vapor. The volatilizing activity has a temperature dependence and heat sensitivity characteristic of enzymatic catalysis and is inducible by mercuric chloride. Ag+ and Au3+ are markedly inhibitory of mercury volatilization.
Citations
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Journal ArticleDOI
TL;DR: The complement of efflux systems of 63 sequenced prokaryotes was compared with that of the heavy metal resistant bacterium Ralstonia metallidurans and showed that heavy metal resistance is the result of multiple layers of resistance systems with overlapping substrate specificities, but unique functions.
Abstract: What makes a heavy metal resistant bacterium heavy metal resistant? The mechanisms of action, physiological functions, and distribution of metal-exporting proteins are outlined, namely: CBA efflux pumps driven by proteins of the resistance–nodulation–cell division superfamily, P-type ATPases, cation diffusion facilitator and chromate proteins, NreB- and CnrT-like resistance factors. The complement of efflux systems of 63 sequenced prokaryotes was compared with that of the heavy metal resistant bacterium Ralstonia metallidurans. This comparison shows that heavy metal resistance is the result of multiple layers of resistance systems with overlapping substrate specificities, but unique functions. Some of these systems are widespread and serve in the basic defense of the cell against superfluous heavy metals, but some are highly specialized and occur only in a few bacteria. Possession of the latter systems makes a bacterium heavy metal resistant.

1,333 citations

Journal ArticleDOI
TL;DR: How this very mobile and plastic suite of proteins protects host cells from this pervasive toxic metal, what roles it has in the biogeochemical cycling of Hg, and how it has been employed in ameliorating environmental contamination are the subjects of this review.
Abstract: Bacterial resistance to inorganic and organic mercury compounds (HgR) is one of the most widely observed phenotypes in eubacteria. Loci conferring HgR in Gram-positive or Gram-negative bacteria typically have at minimum a mercuric reductase enzyme (MerA) that reduces reactive ionic Hg(II) to volatile, relatively inert, monoatomic Hg(0) vapor and a membrane-bound protein (MerT) for uptake of Hg(II) arranged in an operon under control of MerR, a novel metal-responsive regulator. Many HgR loci encode an additional enzyme, MerB, that degrades organomercurials by protonolysis, and one or more additional proteins apparently involved in transport. Genes conferring HgR occur on chromosomes, plasmids, and transposons and their operon arrangements can be quite diverse, frequently involving duplications of the above noted structural genes, several of which are modular themselves. How this very mobile and plastic suite of proteins protects host cells from this pervasive toxic metal, what roles it has in the biogeochemical cycling of Hg, and how it has been employed in ameliorating environmental contamination are the subjects of this review.

941 citations


Cites background from "Mercury Resistance in a Plasmid-Bea..."

  • ...Note that in all cases the rate of Hg(0) oxidation in these Hg(II)-sensitive, plasmid-free bacteria is at least 10-fold lower than the rate of MerA-mediated Hg(II) reduction (see below) observed in bacterial cells carrying a mer operon [106,107] ; thus, hydroperoxidase-mediated oxidation does not generate a futile cycle within a HgR cell....

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Journal ArticleDOI
TL;DR: The environmental and microbiological factors that can influence heavy metal toxicity are discussed with a view to understanding the mechanisms of microbial metal tolerance.
Abstract: The environmental and microbiological factors that can influence heavy metal toxicity are discussed with a view to understanding the mechanisms of microbial metal tolerance. It is apparent that metal toxicity can be heavily influenced by environmental conditions. Binding of metals to organic materials, precipitation, complexation, and ionic interactions are all important phenomena that must be considered carefully in laboratory and field studies. It is also obvious that microbes possess a range of tolerance mechanisms, most featuring some kind of detoxification. Many of these detoxification mechanisms occur widely in the microbial world and are not only specific to microbes growing in metal-contaminated environments.

710 citations

Journal ArticleDOI
01 Jan 1996-Gene
TL;DR: Recently, isolated genes defective in the human hereditary diseases of copper metabolism, namely Menkes syndrome and Wilson's disease, encode P-type ATPases that are more similar to bacterial CadA than to other ATPases from eukaryotes.
Abstract: Bacterial plasmids encode resistance systems for toxic metal ions, including Ag+, AsO2-, AsO4(3-), Cd2+, Co2+, CrO4(2-), Cu2+, Hg2+, Ni2+, Pb2+, Sb3+, TeO3(2-), Tl+ and Zn2+. The function of most resistance systems is based on the energy-dependent efflux of toxic ions. Some of the efflux systems are ATPases and others are chemiosmotic cation/proton antiporters. The Cd(2+)-resistance ATPase of Gram-positive bacteria (CadA) is membrane cation pump homologous with other bacterial, animal and plant P-type ATPases. CadA has been labeled with 32P from [alpha-32P] ATP and drives ATP-dependent Cd2+ (and Zn2+) uptake by inside-out membrane vesicles (equivalent to efflux from whole cells). Recently, isolated genes defective in the human hereditary diseases of copper metabolism, namely Menkes syndrome and Wilson's disease, encode P-type ATPases that are more similar to bacterial CadA than to other ATPases from eukaryotes. The arsenic resistance efflux system transports arsenite [As(III)], alternatively using either a double-polypeptide (ArsA and ArsB) ATPase or a single-polypeptide (ArsB) functioning as a chemiosmotic transporter. The third gene in the arsenic resistance system, arsC, encodes an enzyme that converts intracellular arsenate [As(V)] to arsenite [As(III)], the substrate of the efflux system. The triple-polypeptide Czc (Cd2+, Zn2+ and Co2+) chemiosmotic efflux pump consists of inner membrane (CzcA), outer membrane (CzcC) and membrane-spanning (CzcB) proteins that together transport cations from the cytoplasm across the periplasmic space to the outside of the cell.

628 citations

Journal ArticleDOI
TL;DR: Results show that heavy metal-solubilizing and plant growth promoting bacteria are important for plant growth and heavy metal uptake which may provide a new microbial enhanced-phytoremediation of metal-polluted soils.
Abstract: A heavy metal-resistant bacterial strain was isolated from heavy metal-contaminated soils and identified as Burkholderia sp. J62 based on the 16S rDNA gene sequence analysis. The heavy metal- and antibiotic resistance, heavy metal solubilization of the isolate were investigated. The isolate was also evaluated for promoting plant growth and Pb and Cd uptakes of the plants from heavy metal-contaminated soils in pot experiments. The isolate was found to exhibit different multiple heavy metal and antibiotic resistance characteristics. Atomic absorption spectrometer analysis showed increased bacterial solubilization of lead and cadmium in solution culture and in soils. The isolate produced indole acetic acid, siderophore and 1-aminocyclopropane-1-carboxylate deaminase. The isolate also solubilized inorganic phosphate. Inoculation with the isolate was found to significantly ( p

434 citations

References
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Journal ArticleDOI
TL;DR: A new method for releasing most of the inducible alkaline phosphatases and of the cyclic phosphodiesterase in high yield without greatly impairing the viability of the cells is developed.
Abstract: When Escherichia coli cells are converted into spheroplasts by means of ethylenediaminetetraacetate and lysozyme (1)) most of the inducible alkaline phosphatase (2, 3) is released into the surrounding sucrose-tris(hydroxymethyl)aminomethane-HCl medium (4, 5), and a large fraction of the “latent” ribonuclease (6-8) and the ribonucleic acid inhibited deoxyribonuclease (9) is also set free (lO).r We have since found that three additional enzymes are liberated: a Co tf-stimulated 5’-nucleotidase, not previously described in E. co& an acid phosphatase; and a cyclic phosphodiesterase (11, 12). A total of 10 other enzymes have been examined and found to remain entirely within the spheroplasts. Various lines of evidence suggest that the enzymes which are released occur at or near the cell surface. We have also developed a new method for releasing most of these enzymes in high yield without greatly impairing the viability of the cells. The procedure involves osmotic shock. E. coli are first suspended in a concentrated solution of sucrose, which does not penetrate the cells, and ethylenediaminetetraacetate is added. Then they are suddenly shifted to a medium of low osmotic strength. This causes the release of the phosphatases and of the cyclic phosphodiesterase in a yield of 70% or more. A preliminary report of this work has appeared (13).

1,472 citations

Journal ArticleDOI
16 Aug 1969-Nature
TL;DR: It is reported that both mono and dimethylmercury can be produced in bottom sediments and in rotten fish, and relate the findings to the hazards of mercury pollution.
Abstract: FRESHWATER fish, especially pike (Esox lucius), from Sweden sometimes contain abnormally large amounts of mercury1. It was initially concluded to be either inorganic mercury or phenyl mercury, which are known to be released as industrial wastes, but later it was shown that the mercury was present almost entirely as methyl mercury (CH3Hg+)2. A possible explanation is that living organisms have the capacity to methylate mercury compounds present in pollution. We now report that both mono and dimethylmercury (CH3Hg+ and CH3HgCH3) can be produced in bottom sediments and in rotten fish, and relate the findings to the hazards of mercury pollution.

865 citations

Journal ArticleDOI
12 Oct 1968-Nature
TL;DR: It was discovered later that the spent catalyst of an acetaldehyde reactor, which caused the pollution, contained approximately 1 per cent methyl mercury; and the biological methylation of mercury was thought to be insignificant.
Abstract: THERE have been incidences of extensive alkyl-mercury poisoning in Japan and Sweden. In Japan a large number of people belonging to the fishing population around Minamata Bay were seriously affected by what is now called Minamata disease. This incident was traced back to pollution of the bay with the mercury containing effluent of a large chemical plant. When methyl thiomethyl-mercury was isolated from shellfish in the area of the bay it was suggested that mercury could be alkylated by “plankton and other marine life”2. It was discovered later that the spent catalyst of an acetaldehyde reactor, which caused the pollution, contained approximately 1 per cent methyl mercury; and the biological methylation of mercury was thought to be insignificant.

502 citations