scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Volatilization of mercury by resting mercury-resistant bacterial cells

S. Ghosh1, P. C. Sadhukhan1, Debidas Ghosh1, J. Chaudhuri1, A. Mandal1 
01 Feb 1996-Bulletin of Environmental Contamination and Toxicology (Bull Environ Contam Toxicol)-Vol. 56, Iss: 2, pp 259-264
TL;DR: It is reported that resting cells of mercury-resistant bacteria survive in a buffer system for several hours, synthesize inducible mercury-degrading enzymes and volatilize mercury from a mercury-containing buffer system.
Abstract: The mercuric ion reduction system encoded by the Hg2+ inducible mer operon confers bacterial resistance to mercuric ion. The mer A gene product which is a FAD-containing enzyme catalyzes the reduction of Hg2+ to volatile elemental mercury with the help of intracellular thiols and NADPH as a cofactor (Schottel 1974; Summers and Silver 1978; Fox and Walsh 1982; Misra 1992). Our earlier studies have shown that growing cells of different mercury-resistant bacteria reduce Hg2+ compounds to Hg(O) (Ray et al. 1989; Pahan et al. 1990a; Gachhui et al. 1989). We have also shown the effect of thiol compounds and flavins on mercury-degrading enzyme activities in mercury-resistant bacteria (Pahan et al. 1990b). Here we report that resting cells of mercury-resistant bacteria survive in a buffer system for several hours, synthesize inducible mercury-degrading enzymes and volatilize mercury from a mercury-containing buffer system. We know of no information regarding studies of mercury-degrading enzymes in resting mercury-resistant bacterial cells.
Citations
More filters
01 Jan 2007
TL;DR: The metal uptake ability of Brevibacterium casei and Pseudomonas aeruginosa suggests possibility of using these bacterial strains for removal of mercury from Hg 2+ contaminated.
Abstract: The present study is aimed at assessing the ability of two Hg 2+ resistant bacterial strains, Brevibacterium casei and Pseudomonas aeruginosa, to uptake metal from the medium. For the bacterial isolates the minimum inhibitory concentration of Hg 2+ ranged between 400-500 µg/mL. Pseudomonas aeruginosa could tolerate Pb 2+ (600 µg/mL), Cu 2+ (200 µg/mL), Cd 2+ (50 µg/mL), Zn 2+ (50 µg/mL), Ni 2+ (550 µg/mL) and Cr 6+ (50 µg/mL). Brevibacterium casei, on the other hand, showed resistance against Pb 2+ , Cu 2+ , Cr 6+ , Ni 2+ , Zn 2+ and Cd 2+ at a concentration of 650, 200, 150, 550, 50, and 50 µg/mL, respectively. The isolates showed typical growth curves but lag and log phases extended in the presence of mercury. Both isolates showed optimum growth at 37 oC and pH varying from 7-7.5. Metal processing ability of the isolates was determined in a medium containing 100 µg/mL of Hg 2+ . Pseudomonas aeruginosa could reduce 93% of mercury from the medium after 40 hours and was also capable to remove Hg 2+ 35%, 55% 70% and 85% from the medium after 8, 16, 24 and 32 hours, respectively. Brevibacterium casei could also efficiently remove 80% mercury from the medium after 40 hours and was also able to remove Hg 2+ 20%, 40%, 50%, and 65% from the medium after 8, 16, 24 and 32 hours, respectively. Both bacterial strains have shown remarkable ability to uptake metal ions from the culture medium. Pseudomonas aeruginosa was observed to uptake 80% and Brevibacterium casei 70% of Hg 2+ from the medium after 24 hours of incubation at 37 o C. The metal uptake ability suggests possibility of using these bacterial strains for removal of mercury from Hg 2+ contaminated

43 citations


Cites background from "Volatilization of mercury by restin..."

  • ...Hg○ volatilizes out of the system due to its high vapour pressure (Ghosh et al., 1996)....

    [...]

Journal ArticleDOI
TL;DR: A mercury-hyperresistant strain of Pseudomonas aeruginosa PU21 harboring plasmid Rip64 was utilized to develop bioprocesses able to detoxify and recover soluble mercuric ions in aquatic systems and showed that the specific mercury detoxification rate was dependent on cell growth phases, as well as the initial mercury concentrations.
Abstract: A mercury-hyperresistant strain of Pseudomonas aeruginosa PU21 harboring plasmid Rip64 was utilized to develop bioprocesses able to detoxify and recover soluble mercuric ions in aquatic systems. The kinetics of mercury detoxification was investigated to determine the parameters needed for the design of the bioprocesses. Batch, fed-batch, and continuous bioreactors were utilized to evaluate the efficiency and feasibility of each mode of operation. The results showed that the specific mercury detoxification rate was dependent on cell growth phases, as well as the initial mercury concentrations. Cells at the lag growth phase exhibited the best specific detoxification rate of approximately 1.1 x 10(-6) microg Hg/cell/h, and the rate was optimal at an initial mercury concentration of 8 mg/L. In batch operations with initial mercuric ions ranging from 2 to 10 mg/L, the mercuric ions added were rapidly volatilized from the media in less than 2-3 h. With periodic feeding of 3 or 5 mg Hg/L at fixed time intervals, the fed-batch processes had mercury removal efficiencies of 2.9 and 3.3 mg Hg/h/L, respectively. For continuous operations, the effluent cell concentration (Xe) was essentially invariant at 527 and 523 mg/L with the dilution rates (D) of 0.18 and 0.325 h-1, respectively. The increase in mercury feeding concentrations (Hgf) from 1.0 to 6.15 mg Hg2+/L did not affect the steady-state cell concentration (Xe) but forced the effluent mercury concentration (Hge) to increase. The decrease in the dilution rate, however, resulted in lower Hge values. It was also found that sequential mercury vapor absorption columns recovered over 80% of the Hg degrees released from the bioreactor while the residual mercury vapor was subsequently immobilized by an activated carbon trap in the down stream of the absorption column.

31 citations

Journal ArticleDOI
TL;DR: A wild-type mercury-resistant strain Pseudomonas aeruginosa PU21 (Rip64), and an Escherichia coli PWS1 strain genetically engineered to harbor mercury resistance were examined for their capacity to detoxify soluble mercuric ions with repeated fed-batch operations.

23 citations

Journal ArticleDOI
S. Ghosh1, P. C. Sadhukhan1, J. Chaudhuri1, Debasis Ghosh1, A. Mandal1 
TL;DR: Titration with 5,5′‐dithiobis (2‐nitrobenzoate) demonstrated that two enzyme–SH groups become kinetically accessible on reduction with NADPH, and showed a single band on polyacrylamide gel electrophoresis of the freshly prepared enzyme.
Abstract: Mercury resistance determinants in bacteria are often plasmid-borne or transposon-mediated. Mercuric reductase, one of the proteins encoded by the mercury resistance operon, catalyses a unique reaction in which mercuric ions, Hg (II), are reduced to mercury metal Hg(O) using NADPH as a source of reducing power. Mercuric reductase was purified from Azotobacter chroococcum SS2 using Red A dye matrix affinity chromatography. Freshly purified preparations of the enzyme showed a single band on polyacrylamide gel electrophoresis under non-denaturing conditions. After SDS-polyacrylamide gel electrophoresis of the freshly prepared enzyme, two protein bands, a major and a minor one, were observed with molecular weight 69 000 and 54 000, respectively. The molecular weight of the native enzyme as determined by gel filtration in Sephacryl S-300 was 142 000. The Km of Hg2+-reductase for HgCl2 was 11·11 μmol l−1. Titration with 5,5′-dithiobis (2-nitrobenzoate) demonstrated that two enzyme–SH groups become kinetically accessible on reduction with NADPH.

15 citations


Cites methods from "Volatilization of mercury by restin..."

  • ...Mercuric reductase activity was determined by measuring Hg2¦-induced NADPH oxidation spectrophotometrically at 340 nm following the standard method (Izaki et al. 1974; Ghosh et al. 1996a, b, c)....

    [...]

Journal Article
TL;DR: Pseudomonas aeruginosa and Klebsiella pneumoniae, mercury resistant strains, which are able to grow at 1200 µM HgCl 2 and to reduce mercuric ion to volatile metal mercury, were isolated from hydrocarbons-contaminated river in Morocco.
Abstract: Pseudomonas aeruginosa and Klebsiella pneumoniae, mercury resistant bac- terial strains, which are able to grow at 1200 µM HgCl 2 and to reduce mercuric ion to volatile metal mercury, were isolated from hydrocarbons-contaminated river in Morocco. These bacteria were used for removing mercury from synthetic water polluted by mercu- ry using fixed bioreactor and fluidized bed bioreactor. This mercury bio-decontamination system has permitted to obtain cleanup rates bordering on 100% in both of bioreactors.

14 citations


Cites background from "Volatilization of mercury by restin..."

  • ...This detoxification mechanism is governed by synthesis of flavoprotein mercuric ion reductase ( Ghosh et al., 1996a; Essa et al., 2002; Zeroual et al., 2003)....

    [...]

References
More filters
Journal Article
TL;DR: Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.

289,852 citations

Journal ArticleDOI
TL;DR: It was shown that mercuric reductase has the capacity to accept four electrons per FAD-containing subunit, and that two thiols become kinetically titrable by 5,5'-dithiobis-(2-nitrobenzoate) upon reduction with NADPH, characteristic features of the disulfide reduct enzyme class of flavoproteins.

256 citations

Journal ArticleDOI
01 Jan 1992-Plasmid
TL;DR: Experimental data suggest that the MerR-Hg(II) complex alters the local structure of the promoter region, facilitating initiation of transcription of the mer operon by the RNA polymerase, the most conserved region among these flavin-containing enzymes.

233 citations

Journal ArticleDOI
27 Sep 1974-Nature
TL;DR: THE AUTHORS have screened a large number of R plasmid-bearing Escherichia coli and obtained a few that confer resistance to the organomercurials phenylmercuric acetate (PMA) and methylmerCuric chloride (MMA), which are of interest to see if the mercury(ial) resistance of the bacteria in the alimentary canal influences the fate of ingested mercury(ials).
Abstract: WE have screened a large number of R plasmid-bearing Escherichia coli and obtained a few that confer resistance to the organomercurials phenylmercuric acetate (PMA) and methylmercuric chloride (MMA). Resistance to cationic Hg(II) in E. coli, Staphylococcus aureus and Pseudomonas aeruginosa has invariably been associated with plasmids that also mediate resistance to various antibiotics (R plasmids)1–6. The mechanism of mercury resistance, is the enzymatic reduction of Hg(II) to Hg(0), which is volatile2,7,8. Previously, no organomercurial-reducing E. coli strains have been reported. The only organomercurial-reducing strain studied in detail is a PMA-resistant soil pseu-domonad7–9. As organomercurials including PMA are a human health problem10, it will be of interest to see if the mercury(ial) resistance of the bacteria in our alimentary canal influences the fate of ingested mercury(ials).

175 citations

Book ChapterDOI
01 Jan 1989

52 citations