Phenylmercuric Acetate Research Articles

Distinct genotoxicity of phenylmercury acetate in human lymphocytes as compared with other mercury compounds

In the present study, the frequency of sister chromatid exchanges (SCEs) was assayed to evaluate the genotoxic effects of mercury nitrate (Hg 2+), methylmercury chloride (CH 3HgCl) and phenylmercury acetate (PMA) on human lymphocytes. The free radical scavengers, catalase (CA) and superoxide dismutase (SOD) were tested for their antigenotoxic effects toward PMA. PMA (1–30 μM) increased SCE frequency in a concentration-dependent manner. However, CH 3HgCl significantly increased SCE frequency only at a concentration of 20 μM, and all concentrations treated with Hg 2+ did not induce a positive effect. On the other hand, we first reported that 30 μM Hg 2+, 20 μM CH 3HgCl and (3–30 μM) PMA significantly increased the frequency of endoreduplicated mitosis. PMA was about 3- or 5-fold more effective in inducing endoreduplication than CH 3HgCl or Hg 2+ at equivalent toxic concentrations, respectively. However, neither CA nor SOD in concentrations of 75 and 150 μg/ml showed antagonistic action on the genotoxic effects of PMA. The results suggest that the mechanism of PMA-induced genotoxicity is not mediated by superoxide anion nor H 2O 2. It is concluded that PMA, which was more effective in inducing the elevation of both SCEs and endoreduplication, may be especially hazardous of the three mercury compounds tested.

Inhibition of paraoxonase activity in human liver microsomes by exposure to EDTA, metals and mercurials

Inhibition of paraoxon hydrolase (paraoxonase) activity by ‘in vitro’ exposure to EDTA, Mg 2+, Co 2+ ,Ba 2+, La 2+, Zn 2+, Cu 2+, Hg 2+, p-hydroxymercuribenzoate ( p-OH-MB) and phenyl mercuric acetate (PMA) was investigated in human liver microsomes. Enzyme activity was totally inhibited by 1 mM EDTA in a time-dependent manner, in contrast to previous data obtained in rat liver where an EDTA-resistant fraction was detected. The possible influence of postmortem changes in these results was checked in a parallel experiment using rat livers with different postmortem intervals. From our results the existence in human liver of an EDTA-resistant fraction cannot be discarded. Ba, La and PMA showed immediate inhibition. By contrast the other compounds tested were time-dependent inhibitors. Ba and Zn showed the highest IC 50 values. Cu and mercurials (Hg, p-OH-MB, PMA) were the most potent inhibitors of human liver paraoxonase. Kinetic analysis (Lineweaver-Burk and Dixon plots) indicated that different inhibitors exhibit different inhibition patterns: competitive (EDTA, Ba, La, Cu, p-OH-MB and PMA), non competitive (Zn) and mixed (Hg). The pretreatment of sample with dithiothreitol (DTT) protects against the inhibitory effect of mercurials. Furthermore after inhibition by mercurials the activity was restored by DTT. These results confirmed the essential role of the -SH groups to maintain the catalytic activity of paraoxonase and suggest the existence of two types of -SH groups that could differ in their localization.

Compatibility of phenylmercuric acetate with cefuroxime and ceftazidime eye drops

The compatibility of the antimicrobial preservative phenylmercuric acetate (0.002% w/v) was studied with the cephalosporin antibiotics cefuroxime and ceftazidime (5% w/v), using pre-column derivatisation HPLC. The formulations were stored in amber glass eye drop bottles, at 7 and 25°C. Phenylmercuric acetate was unstable at both temperatures in the presence of either antibiotic. At 25°C, there was complete degradation in 14 days.

Mercury and organomercurial resistance in bacteria isolated from freshwater fish of wetland fisheries around Calcutta

Mercury-resistant bacteria belonging to the genera Bacillus, Escherichia, Klebsiella, Micrococcus, Pseudomonas, Salmonella, Sarcina, Shigella, Staphylococcus and Streptococcus were isolated from gills and guts of fresh water fish collected from wetland fisheries around Calcutta, India, contaminated with mercury compounds. The total number of bacteria, as well as Hg-resistant bacteria, were always higher in guts than gills. Bottom-dwelling fish contained higher number of bacteria, including Hg-resistant bacteria, than surface and middle water dwelling fish. They belonged either to narrow-spectrum or to broad-spectrum Hg-resistant groups and they also possessed other heavy metal and antibiotic resistant properties. In the presence of toxic levels of HgCl 2, phenylmercuric acetate (PMA) and methylmercuric chloride (MMC), the lag in growth of the bacterial strains gradually increased with increasing concentration of Hg-compounds. Narrow-spectrum Hg-resistant bacterial strains volatilized only HgCl 2 from the liquid medium in the range of 64–89%, whereas the broad-spectrum group exhibited a high level of HgCl 2 (80–94%), PMA (72–84%) and MMC (64–80%) volatilizing capacity with inducible mercuric reductase and organomercurial lyase enzyme activities in their cell-free extracts. Cell-free extracts prepared from narrow-spectrum Hg-resistant bacterial strains induced by HgCl 2 exhibited Hg +2-dependent NADPH oxidation, indicating the presence of only mercuric reductase enzyme.

Symmetrisation, isomerism and structural studies on novel phenylmercury(II) thiosemicarbazonates: correlation of the energy barrier to rotation of the amino group with the bonding parameters of the thioamide group

The reactions of phenylmercury(II) acetate with a series of alkyl, aryl and heterocyclic thiosemicarbazones in ethanol formed novel phenylmercury(II) derivatives of stoichiometry [HgPhL] [HL = RN3N2HC1(S)N1H2 = cyclopentanone 1, cyclohexanone 2, benzaldehyde 3, 2-hydroxybenzaldehyde 4, 4-methoxybenzaldehyde 5, pyrrole-2-carbaldehyde 6, thiophene-2-carbaldehyde 7 or furan-2-carbaldehyde 8 thiosemicarbazone], characterised with the help of analytical data, physical properties, IR, far-IR, multinuclear NMR (1H, 13C, 199Hg) spectroscopy and X-ray crystallography of complexes 1, 5 and 6. The 1H and 13C NMR data suggest that the N2H group is deprotonated during reaction with phenylmercury(II) acetate and co-ordination occurs via the N3,S atoms in a chelating mode. The 199Hg NMR data suggest symmetrisation phenomenon for complexes 3 and 5, 2[HgPhL] ⇌ HgPh2 + [HgL], which is supported also by 1H and 13C NMR data. The δ(Hg) values reveal that shielding of Hg with the change of organic group in the thiosemicarbazones decreases in the order: 2-hydroxybenzene ⋙ furan > benzene > 4-methoxybenzene thiophene ≈ cyclohexanone ≈ cyclopentanone > pyrrole and the Lewis basicity of the thiosemicarbazones varies in the opposite order. The 1H and 13C NMR data reveal that 7 and 8 show isomerism. There are two strong [Hg–C 2.063(7) 1, 2.069(10) 5, 2.049(11) 6; Hg–S 2.382(2) 1, 2.357(3) 5, 2.377(3) A 6] and one weak bond [Hg–N3 2.489(6) 1, 2.611(7) 5, 2.492(9) A 6], with CPh–Hg–S bond angles of 162.9(2), 174.2(3), 165.8(3)° respectively. The weak intermolecular interactions via Hg · · · N2 [3.001(6) A] in 1 and via Hg · · · S in 5 [3.518(3) A] and 6 [3.528(3) A] form centrosymmetric dimers and Hg formally acquires four-co-ordination with two strong (Hg–C, Hg–S), one weak (Hg · · · N3) and one secondary (Hg · · · N2 or S) bonds. The preferred dimer formation via N2 nitrogen in 1, rather than via sulfur atoms (5 and 6) despite Hg · · · S affinity represents an unusual bonding mode. From the low-temperature 1H NMR studies of some selected complexes, the energy barrier (ΔGTc*, Tc is coalescence temperature) to rotation of the amino group about the C1–N1 bond was calculated and correlated with bonding parameters of the thioamide group in the solid state.

Genetically modified Escherichia coli for colorimetric detection of inorganic and organic Hg compounds.

A sensitive colorimetric bacterial system was developed for the detection of Hg(II) and organomercury compounds. The bioactive species, a recombinant Escherichia coli, produces proportionally elevated levels of the enzyme beta-galactosidase with increasing amounts of Hg. This is due to a reporter plasmid which carriers a Hg(II)-inducible promoter (mer promoter) from the Hg resistance transposon Tn501 regulating the transcription of a promoterless lacZ gene. Additionally, a pMB1 origin of replication without the natural RNA polymerase start site is fused downstream of the mer promoter leading to a Hg(II)-inducible plasmid replication, which results in an improved signal-to-noise ratio. To enhance the sensitivity of this cellular biosensor, the transport proteins for Hg(II) uptake are constitutively produced by a helper plasmid. To enable the detection of organically bound Hg, the Streptomyces lividans organomercurical lyase, an enzyme which catalyses the cleavage of C-Hg-bonds of organomercurial compounds, is also provided by the helper plasmid. Hg(II) and phenylmercuric acetate (PMA) concentrations as low as 5 x 10(-10) M (0.1 ppb) may be detected within a few minutes.

Synthesis, structure and spectral properties of [(HgPh) 2TbSMe]; a dinuclear 2- S-methylthiobarbiturate of phenylmercury(II) exhibiting linkage isomerism

The reaction of 2- S-methylthiobarbituric acid (H 2TbSMe) with phenylmercury(II) acetate in ethanol afforded the title complex, which crystallizes in the space group P2 1/ c (No. 14). The asymmetric unit consists of two independent [(HgPh) 2TbSMe] molecules: in molecule 1, the two organometallic moieties are bound primarily to the nitrogen atoms of the ligand ring (N(1) and N(3)); in molecule 2, one phenylmercury(II) is N(1)-bound but the other is bound to the exocyclic oxygen contiguous to N(3). Hence molecules 1 and 2 are linkage isomers. Several weak intra- and intermolecular interactions are also observed. In DMSO solution, 1H, 13C and 199Hg NMR measurements suggest fast exchange of phenylmercury(II) between N- and O-coordination, with prevalence of the former.

Regulation of the operon responsible for broad-spectrum mercury resistance in Streptomyces lividans 1326.

The broad-spectrum mercury resistance of Streptomyces lividans 1326 is mediated by six open reading frames (orf). These are arranged in two divergently transcribed operons. The orfs mer A (mercuric reductase) and mer B (organolyase) form one of the two operons. These genes and their regulation were further studied by deletion analysis and transcriptional fusion to the reporter gene xylE in the plasmid pXE4. An increase in XylE activity in response to the presence of mercuric ions was observed. The function of ORF2 (MerT) and ORF3 (MerP) as mercury-specific transport proteins, previously postulated based on the structural features of the predicted proteins, was confirmed. Transcription of the mer genes starts within the intercistronic region and two divergent promoters were identified by S1 nuclease mapping. Expression of the genes was negatively regulated by the product of orf1, now called merR. The repressor function was confirmed by gel retardation assays. MerR, produced in Escherichia coli, bound to two sites (operators) in the fragment containing the promoter region between merA and merR. Addition of mercuric ions and phenylmercuric acetate prevented the binding of MerR.

In vitro activation of human fibroblasts by retrieved titanium alloy wear debris

Titanium-aluminum-vanadium wear particles isolated from the soft-issue membrane of a failed total hip arthroplasty were added to human fibroblasts in cell culture. The cellular response to particle challenge was determined by assaying for levels of interleukin-1 beta, interleukin-6, tumor necrosis factor-alpha, prostaglandin E2, basic fibroblast growth factor, platelet-derived growth factor-AB, and transforming growth factor-beta. Collagenase and gelatinase activities were analyzed by zymography and [3H]collagen degradation. Cell viability was assessed by measuring the uptake of [3H]thymidine. Over the range of particle concentrations tested, cell viability, as demonstrated by [3H]thymidine uptake, remained unaffected. Fibroblasts exhibited a dose-dependent release of interleukin-6 in response to exposure to titanium-aluminum-vanadium particles. At 6 and 48 hours, the highest concentration of titanium alloy particles (0.189% [vol/vol]) resulted in 7-fold and 16-fold increases in interleukin-6 release, respectively, when compared with negative controls. Neither interleukin-1 beta nor tumor necrosis factor-alpha was detected in the culture medium at any particle concentration tested for both dermal and foreskin fibroblasts. The pattern of prostaglandin E2 release by fibroblasts mirrored the pattern of interleukin-6 release. Fibroblasts exposed to the highest concentration of titanium alloy particles showed an increase in collagenase activity, starting at 12 hours. When medium samples were treated with amino phenylmercuric acetate to activate latent enzymes, a statistically significant increase in collagenase activity was observed as early as 6 hours (p < 0.001). Substrate gel analysis of medium from fibroblasts stimulated by high particle concentrations also showed an increase in gelatinolytic activity when compared with unstimulated controls. Analysis of medium samples for growth factors showed an increase in basic fibroblast growth factor at low particle concentrations, beginning at 12 hours. Levels of platelet-derived growth factor-AB and transforming growth factor-beta were not detectable in the controls or at any particle concentration tested. The results of this study showed that fibroblasts exposed to titanium alloy wear particles become activated and release proinflammatory mediators that influence bone metabolism. These data support the hypothesis that direct activation of fibroblasts by particulate wear may play a role in particle-mediated osteolysis. Fibroblast activation coupled with the biologic response of macrophages to wear debris in the loosening membrane may have a synergistic effect on pathologic bone resorption.

Psychological and somatic subjective symptoms as a result of dermatological patch testing with metallic mercury and phenyl mercuric acetate

Sixty patients with a history of malaise over the ensuing weeks following the drilling out of old amalgam fillings were included in the study. They were tested epicutaneously weekly (standard procedure) with either 0.5% metallic mercury in petrolatum or 0.01% phenyl mercuric acetate in water, and, on 2 separate occasions, with only saline or petrolatum as a control according to a randomized double-blind protocol. The presence or absence of an allergic patch test response was read on day 3. Two patients showed allergic cutaneous responses towards metallic mercury and 1 to phenyl mercuric a.cetate. There was a concurrent 7-day self-registration of subjective psychological and somatic symptoms, using a validated visual analogue scale (minor symptom evaluation profile; MSE). In the group analysis it was clearly shown that the patients reacted with subjective symptoms to phenyl mercuric acetate. A reaction to test doses of metallic mercury seems to exist but could only be visualized when a scoring system was elaborated to individually define those subjects with a psychological and somatic response to test doses of mercury. This psychosomatic reactivity, named intolerance, seems to be unrelated to the cutaneous delayed allergic skin response. Thus, it might be possible to identify patients intolerant to small test doses of percutaneously penetrating mercury (previously considered innocuous). These findings may have a bearing on the systemic side-effects attributed to mercury released from amalgam tooth fillings.

The Photoactivated Cross-linking of Recombinant C-terminal Domain to Proteins in a HeLa Cell Transcription Extract That Comigrate with Transcription Factors IIE and IIF

The C-terminal domain (CTD) of RNA polymerase II (RNAP II) is essential for the assembly of RNAP II into preinitiation complexes on some promoters such as the dihydrofolate reductase (DHFR) promoter. In addition, during the transition from a preinitiation complex to a stable elongation complex, the CTD becomes heavily phosphorylated. In this report, interactions involving the CTD have been examined by protein-protein cross-linking. As a prelude to the study of CTD interactions, the effect of recombinant CTD on in vitro transcription was examined. The presence of recombinant CTD inhibits in vitro transcription from both the DHFR and adenovirus 2 major late promoters, suggesting that the CTD is involved in essential interactions with a general transcription factor(s). Factors in the transcription extract that interact with the CTD were identified by protein-protein cross-linking. Recombinant CTD was phosphorylated at its casein kinase II site, at the C terminus of the CTD, in the presence of [35S]adenosine 5'-O-(thiotriphosphate) and alkylated with azidophenacyl bromide. Incubation of azido-modified 35S-labeled CTD with a HeLa transcription extract followed by ultraviolet irradiation results in the covalent cross-linking of the CTD to proteins in contact with the CTD at the time of irradiation. Subsequent incubation with phenylmercuric acetate results in the transfer of 35S from the CTD to the protein to which it was cross-linked. The two major photolabeled bands have a M(r) of 34,000 and 74,000. The specificity of CTD interactions was demonstrated by a reduction in photolabeling in the presence of unmodified CTD or RNAP II containing an intact CTD (RNAP IIA) but not in the presence of a CTD-less RNAP II (RNAP IIB). The 35S-labeled 34- and 74-kDa proteins comigrate on SDS-polyacrylamide gel electrophoresis with the beta subunit of transcription factor IIE and the 74-kDa subunit of transcription factor IIF, respectively. Moreover, some of the minor 35S-labeled bands comigrate with other subunits of the general transcription factors.

Determination of mercury species in gas condensates by on‐line coupled high‐performance liquid chromatography and cold‐vapor atomic absorption spectrometry

AbstractA method for the speciation of mercury in gas condensates is reported. Mercury(II) chloride (HgCl2), methylmercury chloride (MeHgCl), phenylmercury acetate (PhHgAc) and diphenylmercury (Ph2Hg) are separated by reversed‐phase high‐performance liquid chromatography (HPLC) using gradient elution. Prior to the determination, the organic ligands and the matrix were destroyed by oxidation with K2Cr2O7. Mercury is detected with cold‐vapor atomic absorption spectrometry (CVAA), where the mercury compounds are reduced to metallic mercury by a treatment with NaBH4. In a continuous‐flow system the concentrations of the reagents used are optimized using a modified simplex algorithm. Detection limits for mercury are at the 10 ng ml−1 level. Analysis of multi‐compound mixtures indicates that chemical reactions between HgCl2 and Ph2Hg and between MeHgCl and Ph2Hg take place. The method developed was applied to the speciation of mercury in gas condensates and did not require use of any solvent extraction or chemical derivatization steps. In the gas condensates, mercury(II) compounds were found to be present at the 100 ng ml−1 level.

アスペルギルスによる猫耳真菌症の2例

Two cases of feline otomycosis caused byAspergillusspp. were reported. The animals showed intense itching, accumulation of rustbrown or brown-black coloured cerumen and slight redness on the ear canal. A large amount of septate hyphae and a small amount of condidial heads of Aspergillus spp. were demonstrated in both KOH-mount and Gramstained preparations of the ear-swabs, and Aspergillus nidulansandA. terreuswere respectively isolated from these cases. By washing or cleaning with 0.1% phenyl mercuric acetate solution and topical administration of miconazole every 3 to 7 days, both cases were recovered in 1 or 2 months.

Preservative efficacy in cefuroxime and ceftazidime eye drop formulations

The efficacy of various common antimicrobial preservatives was tested in eye drop formulations containing the cephalosporin antibiotics cefuroxime and ceftazidime. The British Pharmacopoeia test for the efficacy of antimicrobial preservatives was used and the formulations were challenged with Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans. The survival of organisms was monitored over 14 days. Cefuroxime sodium, 50 mg/ml, was studied in simple aqueous solution, and dissolved in an artificial tear formulation, Sno Tears (Smith and Nephew Pharmaceuticals), which contains benzalkonium chloride 0.004% w/v. Ceftazidime (50 mg/ml) was also studied in these two vehicles and, in addition, in a phenylmercuric acetate solution (0.002% w/v) and chlorhexidine acetate (0.02% w/v). Cefuroxime and ceftazidime contributed little, in the short-term, towards a microbicidal preservative effect in the unpreserved aqueous formulations, even against organisms for which they were active. Cefuroxime was adequately preserved in a vehicle of Sno Tears, which contains benzalkonium chloride as the antimicrobial preservative. Ceftazidime was less well preserved in this vehicle, but it was superior to phenylmercuric acetate (0.002% w/v) or chlorhexidine acetate (0.02% w/v).

Purification and characterization of a novel organometallic receptor protein regulating the expression of the broad spectrum mercury-resistant operon of plasmid pDU1358.

The narrow spectrum mercury-resistant (mer) operons of transposons Tn21 and Tn501 are inducible by inorganic mercury salts. The major regulatory gene merR is transcribed divergently from the other mer genes, which are cotranscribed. The MerR protein represses its own expression, as well as the expression of the other mer genes in the absence of the inducers. The synthesis of the polycistronic mer message is stimulated by MerR in the presence of the inducers. The MerRBS protein encoded by the broad spectrum mer operon of plasmid pDU1358 was characterized as a novel organomercurial receptor, distinguishing it from the narrow spectrum MerRNS proteins, described above. Several organomercurial compounds directly effected cellular activation of the mer operon transcription via the receptor protein MerRBS, but not by MerRNS. The merR gene from pDU1358 was cloned under the tac promoter, and the overexpressed MerRBS protein was soluble in buffer solutions containing 0.5 M NaCl at pH 7.5, but precipitated when NaCl concentration was reduced to 0.1 M (MerRBS concentrations at or above 0.1 mg/ml). MerRBS was purified to near homogeneity by selective precipitation and solubilization by varying the salt concentration in buffer solutions, followed by Sephadex G-75 column chromatography. Both MerRBS and Tn21-encoded MerRNS bound with DNA fragments containing the pDU1358 mer operator sequence with comparable affinities. In vitro run-off transcription studies revealed that MerRBS activated mer operon expression in the presence of Hg2+ or phenylmercuric acetate. Phenylmercuric acetate did not induce mer operon expression when the MerRNS was used in the assay.

Mercury compounds induce a rapid increase in procoagulant activity of monocyte-like U937 cells.

When monocytic leukaemia line U937 cells were incubated in the presence of HgCl2 there was a rapid increase in tissue factor (TF)-dependent procoagulant activity, reaching a maximum (equivalent to the total TF activity observed when cells had been subjected to a freeze/thaw cycle) after 15 min at 50 microM HgCl2 and after 30 min at 10 microM HgCl2. Two other heavy metal compounds, AgNO3 and phenylmercuric acetate, caused a similar increase in TF activity. The increase was independent of protein synthesis. Other reagents tested, CdCl2, ZnCl2, NiCl2, ADP, FMLP and monocyte chemotactic factor (MCF-1), did not cause a rapid increase in functional activity, when tested under the same experimental conditions. The addition of HgCl2 to the cells causes, in a concentration-dependent manner, a 10-12-fold increase in intracellular calcium (Cai) which coincides with increase in TF activity. Calcium ionophore also caused an increase in TF activity of the U937 cells. Upon treatment with HgCl2 the cell surface of U937 cells showed a large increase in the level of phosphatidylserine (PS) on the cell surface (as measured by potentiation of the rate of activation of prothrombin by factor Xa-factor Va) but with no change in the level of TF antigen on the cell surface. We consider that the TF is present on the cell surface of the monocyte but relatively inactive towards the physiological substrate, factor X (FX), until HgCl2 causes a change in the polarity of the cell membrane exposing PS on the outer leaflet by a mechanism likely to be enhanced by the increase in intracellular calcium.

The cyclic electron pathways around photosystem I in Chlamydomonas reinhardtii as determined in vivo by photoacoustic measurements of energy storage

The photoacoustic technique was used to measure energy storage by cyclic electron transfer around photosystem I in intact Chlamydomonas reinhardtii cells illuminated with far-red light (>715 nm). The in-vivo cyclic pathway was characterized by investigating the effects of various chemicals on energy storage. Participation of plastoquinone and ferredoxin in the cyclic electron flow was confirmed by the complete suppression of energy storage in the presence of the plastoquinol antagonist 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) and the ferredoxin inhibitors/competitors methylviologen, phenylmercuric acetate and p-benzoquinone. Two alternative electron cycles are demonstrated to operate in vivo. One cycle is sensitive to antimycin A, myxothiazol and 2-(n-heptyl)-4-hydroxyquinoline N-oxide (HQNO) and is catalyzed by ferredoxin which reduces plastoquinone through a route involving cytochrome b 6 and its protonmotive Q-cycle. The other cycle is unaffected by the above-mentioned inhibitors but is sensitive to N-ethylmaleimide (NEM), an inhibitor of the ferredoxin-NADP reductase, and 2′-monophosphoadenosine-5′-diphosphoribose (PADR), an analogue of NADP, showing that the electron recycling was mediated by NADPH. Possibly, electrons enter the plastoquinone pool through the action of a NAD(P)H dehydrogenase, which is insensitive to classical inhibitors of the mitochondrial NADH dehydrogenase. Loss of energy storage by photosystem-I-driven cyclic electron transfer in farred light was observed only when antimycin A, myxothiazol or HQNO was used in combination with NEM or PADR. Analysis of the light-intensity dependence and the rate of in-vivo cyclic electron transfer in the presence of various inhibitors indicates that the NADPH-dependent electron-cycle is the preferential cyclic pathway in Chlamydomonas cells illuminated with far-red light.

Cloning and expression of the mercury resistance genes of marine Pseudomonas sp. strain MR1 plasmid pMR1 in Escherichia coli

The mercury resistance determinant of marine Pseudomonas sp. strain MR1 plasmid pMR1 was cloned into a narrow-host-range vector pUC18. A direct selection of mercury resistant clones was successful and 12 clones were evolved; 9 from direct selection on mercury agar plates and 3 from ampicillin-resistant white colonies. All the predicted clones efficiently volatilized mercury. One of the hybrid plasmids pMRD5, containing a 15.5-kb insert, conferred inducible resistance to both HgCl 2 and phenyl mercury acetate with over a 40-fold increase in mer resistance in Escherichia coli HB 101. No DNA homology existed between the mer operon of Pseudomonas sp. strain MR1 and the characterized determinants of Tn 501 mer DNA.

Pseudomonas putida Strains Which Constitutively Overexpress Mercury Resistance for Biodetoxification of Organomercurial Pollutants

Improved biocatalysts for mercury (Hg) remediation were generated by random mutagenesis of Pseudomonas putida with a minitransposon containing merTPAB, the structural genes specifying organomercury resistance. Subsequent selection for derivatives exhibiting elevated resistance levels to phenylmercury allowed the isolation of strains that constitutively express merTPAB at high levels, conferring the ability to cleave Hg from an organic moiety and reduce the freed Hg(II) to the less toxic elemental form, Hg, at greater rates. Constitutive overexpression of merTPAB had no apparent effect on culture growth rates, even when Hg(II) was initially present at otherwise toxic concentrations. These properties were also combined with benzene and toluene catabolism, allowing detoxification of the metal component of phenyl mercuric acetate, as well as degradation of its aromatic moiety.

Use of indirect 199Hg NMR detection for aromatic mercury compounds of biological interest

AbstractWhen vanillin (4‐hydroxy‐3‐methoxbenzaldehyde) and syringaldehyde (4‐hydroxy‐3,5‐dimethoxybenzaldehyde) react with Hg(OAc)2, selective monomercuration occurs on the aromatic ring. The three 3J, 4J and 5(199Hg,1H) coupling constants of phenylmercury acetate were used as 1/2J delays in the 1D inverse 1H 199Hg, sequence applied to 5‐acetoxymercuriovanillin and 2‐acetoxymercuriosyringaldehyde, the edited proton spectra obtained for each nJ(199Hg, 1H) coupling gave the value of n and the J(199Hg, 1H) coupling constants, and therefore yielded information about the position of the mercury substitution on the aromatic ring. A 2D 199Hg,1H shift correlation with 1H detection was applied in the case of phenylmercury acetate, using the mean value of the three J couplings; the 3J and 4J couplings were clearly resolved. As vanillin and syringaldehyde are representative monomer models of lignin, the indirect detection of 199Hg is then an appropriate method to determine the aromatic substitution pattern, which is a key point in lignin structural elucidation.