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PubMed1998

Selenium content of sulfide ores related to ophiolites of Greece.

Several deposits of sulfide mineralization have been described in the ophiolites of Greece. Based on their mineralogical and chemical composition and the host rocks, two types can be distinguished: (1) the Fe-Cu-Ni-Co type consisting of pyrrhotite, chalcopyrite, Co-pentlandite, pyrite, magnetite + arsenides, +/- chromite, hosted in serpentinites, gabbros or diabases, which have variable geochemical characteristics, and (2) sulfide mineralization of the Cyprus type containing variable proportions of pyrite, chalcopyrite, bornite, and sphalerite. The spatial association with shear zones and fault systems, which is a common feature in both types of mineralization, provided the necessary permeability for the circulation of the responsible mineralized hydrothermal fluids. The selenium (Se) content in representative samples of both types of mineralization from the ophiolites of Pindos (Kondro, Perivoli, and Neropriona), Othrys (Eretria and A. Theodoroi), Veria (Trilofon), and Argolis (Ermioni) shows a wide variation. The highest values of Se (130 to 1900 ppm) were found in massive Fe-Cu sulfide ores from Kondro, in particular the Cu-rich portions (average 1300 ppm Se). The average values of Se for the Othrys sulfides are low (< 40 ppm Se). The Se content in a diabase breccia pipe (50 x 200 m) with disseminated pyrite mineralization (Neropriona) ranges from < 1 to 35 ppm Se. The highest values were noted in strongly altered samples that also exhibited a significant enrichment in platinum (1 ppm Pt). Sulfide mineralization (irregular to lens-like masses and stringers) associated with magnetite, hosted in gabbros exposed in the Perivoli area (Tsouma hill), shows a content ranging from 40 to 350 ppm Se. The distribution of Se in the studied type of the sulfide mineralization may be of genetic significance, indicating that the Se level, which often is much higher than in typical magmatic sulfides related to mafic-ultramafic rocks (average 90-100 ppm Se), may positively affect the environment.

Environment↗
PubMed1988

Chromosomal changes in cell lines from mouse tumors induced by nickel sulfide and methylcholanthrene.

Rhabdomyosarcomas were induced in mice by intramuscular injections of crystalline nickel sulfide and 3-methylcholanthrene. At early passage, karyotypes were performed by G-banding for four nickel sulfide cell lines and for three 3-methylcholanthrene cell lines. Six cell lines were near-diploid and one nickel sulfide line was near-tetraploid. Three of the nickel sulfide cell lines were characterized by a rearranged marker chromosome which was present in a majority of the cells of each line. The rearrangements leading to the formation of marker chromosomes were different in each nickel sulfide cell line but involved chromosome 4 in two of the nickel sulfide cell lines. Extra copies of chromosome 15 were present in two nickel sulfide cell lines. Possible rearrangement and/or gene activation was examined for the c-mos oncogene on chromosome 4 and the c-myc oncogene on chromosome 15, but no alteration or activation was observed. None of the 3-methylcholanthrene cell lines contained rearranged marker chromosomes; however, one MCA cell line did contain large numbers of double minutes. In all cell lines, minichromosomes (small atypical acrocentric chromosomes) were observed that contained distinct centromeric regions but no other G-positive bands.

Aneuploidy↗
PubMedDate not supplied

Age-related changes in sulfide-silver stainable fibres in the rat cerebral cortex.

The present study was designed to assess the age-dependent changes in sulfide-silver stainable fibres in frontal, parietal and occipital cortex areas of the rat cerebral cortex. Male Sprague-Dawley rats of 2 months (young), 12 months (adult) and 24 months (aged) were used. Sulfide-silver stainable fibres, which represent predominantly zinc-containing associational fibres arising from local cortical interneurons, were visualized using the neo-Timm histochemical technique. The density of sulfide-silver stainable fibres within the neuropil of laminae I-III (upper zone) and of lamina V (lower zone) of the different cerebral cortex areas was assessed microdensitometrically. In the frontal and parietal cortices the density of sulfide-silver stainable fibres was higher in adult and in aged than in young rats both in the upper and in the lower zones. No significant differences were noticeable in the density of sulfide-silver stainable fibres between adult and old rats. In the occipital cortex the density of sulfide-silver stainable fibres was similar in young or adult rats. but was remarkably increased in old animals. The possibility that the increase in the density of sulfide-silver stainable fibres represents a compensatory mechanism in the cerebral cortex area showing the most consistent nerve cell loss is discussed.

Journal Article↗
PubMed2004

Sulfide dehydrogenase activity of the monomeric flavoprotein SoxF of Paracoccus pantotrophus.

Flavocytochrome c-sulfide dehydrogenases (FCSDs) are complexes of a flavoprotein with a c-type cytochrome performing hydrogen sulfide-dependent cytochrome c reduction in vitro. The amino acid sequence analysis revealed that the phylogenetic relationship of different flavoproteins reflected the relationship of sulfur-oxidizing bacteria. The flavoprotein SoxF of Paracoccus pantotrophus is 29-67% identical to the flavoprotein subunit of FCSD of phototrophic sulfur-oxidizing bacteria. Purification of SoxF yielded a homogeneous emerald-green monomeric protein of 42 797 Da. SoxF catalyzed sulfide-dependent horse heart cytochrome c reduction at the optimum pH of 6.0 with a k(cat) of 3.9 s(-1), a K(m) of 2.3 microM for sulfide, and a K(m) of 116 microM for cytochrome c, as determined by nonlinear regression analysis. The yield of 1.9 mol of cytochrome c reduced per mole of sulfide suggests sulfur or polysulfide as the product. Sulfide dehydrogenase activity of SoxF was inhibited by sulfur (K(i) = 1.3 microM) and inactivated by sulfite. Cyanide (1 mM) inhibited SoxF activity at pH 6.0 by 25% and at pH 8.0 by 92%. Redox titrations in the infrared spectral range from 1800 to 1200 cm(-1) and in the visible spectral range from 400 to 700 nm both yielded a midpoint potential for SoxF of -555 +/- 10 mV versus Ag/AgCl at pH 7.5 and -440 +/- 20 mV versus Ag/AgCl at pH 6.0 (-232 mV versus SHE') and a transfer of 1.9 electrons. Electrochemically induced FTIR difference spectra of SoxF as compared to those of free flavin in solution suggested a strong cofactor interaction with the apoprotein. Furthermore, an activation/variation of SoxF during the redox cycles is observed. This is the first report of a monomeric flavoprotein with sulfide dehydrogenase activity.

Amino Acid Sequence↗
PubMed1998

Sulindac sulfide inhibits Ras signaling.

The non-steroidal anti-inflammatory drug sulindac is used in cancer prevention and therapy, but the molecular aspects of its anti-tumor effect remain unresolved. In vivo the prodrug sulindac, is converted into the metabolite sulindac sulfide. We found that sulindac sulfide strongly inhibits Ras induced malignant transformation and Ras/Raf dependent transactivation. Sulindac sulfide decreases the Ras induced activation of its main effector, the c-Raf-1 kinase. In vitro sulindac sulfide directly binds to the Ras gene product p21ras in a non-covalent manner. Moreover, we can show that sulindac sulfide inhibits the interaction of p21ras with the p21ras binding domain of the Raf protein. In addition, sulindac sulfide can impair the nucleotide exchange on p21ras by CDC25 as well as the acceleration of the p21ras GTPase reaction by p120GAP. Due to its action at the most critical site in Ras signaling we propose sulindac sulfide as a lead compound in the search for novel anti-cancer drugs which directly inhibit Ras mediated cell proliferation and malignant transformation.

3T3 Cells↗
PubMed1981

Technique for simultaneous determination of [s]sulfide and [C]carbon dioxide in anaerobic aqueous samples.

A technique for the simultaneous determination of [S]sulfide and [C]carbon dioxide produced in anaerobic aqueous samples dual-labeled with [S]sulfate and a C-organic substrate is described. The method involves the passive distillation of sulfide and carbon dioxide from an acidified water sample and their subsequent separation by selective chemical absorption. The recovery of sulfide was 93% for amounts ranging from 0.35 to 50 mumol; recovery of carbon dioxide was 99% in amounts up to 20 mumol. Within these delineated ranges of total sulfide and carbon dioxide, 1 nmol of [S]sulfide and 7.5 nmol of [C]carbon dioxide were separated and quantified. Correction factors were formulated for low levels of radioisotopic cross-contamination by sulfide, carbon dioxide, and volatile organic acids. The overall standard error of the method was +/-4% for sulfide and +/-6% for carbon dioxide.

Journal Article↗
PubMed2006

Sulindac sulfide and exisulind inhibit expression of the estrogen and progesterone receptors in human breast cancer cells.

In previous studies, we found that sulindac sulfide and exisulind (sulindac sulfone, Aptosyn) cause growth inhibition, arrest cells in the G1 phase of the cell cycle, and induce apoptosis in human breast cancer cell lines. These effects were associated with decreased expression of cyclin D1. The present study focuses on the effects of sulindac sulfide and exisulind on hormone signaling components in breast cancer cells. We found that estrogen receptor (ER)-positive and progesterone receptor (PR)-positive T47D breast cancer cells were somewhat more sensitive to growth inhibition by sulindac sulfide or exisulind than ER-negative PR-negative MB-MDA-468 breast cancer cells. Further studies indicated that sulindac sulfide and exisulind caused marked down-regulation of expression of the ER and PR-A and PR-B in T47D cells. However, neither compound caused a major change in expression of the retinoic acid receptor alpha (RARalpha), RARbeta, or RARalpha in T47D cells. Sulindac sulfide and exisulind also caused a decrease in expression of the ER in estrogen-responsive MCF-7 breast cancer cells. Both compounds also markedly inhibited estrogen-stimulated activation of an estrogen-responsive promoter in transient transfection reporter assays. Treatment of T47D cells with specific protein kinase G (PKG) activators did not cause a decrease in ER or PR expression. Therefore, although sulindac sulfide and exisulind can cause activation of PKG, the inhibitory effects of these two compounds on ER and PR expression does not seem to be mediated by PKG. Our findings suggest that the growth inhibition by sulindac sulfide and exisulind in ER-positive and PR-positive human breast cancer cells may be mediated, in part, by inhibition of ER and PR signaling. Thus, these and related compounds may provide a novel approach to the prevention and treatment of human breast cancers, especially those that are ER positive.

Breast Neoplasms↗
PubMed2006

The hydrocarbon seep tubeworm Lamellibrachia luymesi primarily eliminates sulfate and hydrogen ions across its roots to conserve energy and ensure sulfide supply.

Lamellibrachia luymesi (Polychaeta, Siboglinidae) is a deep-sea vestimentiferan tubeworm that forms large bush-like aggregations at hydrocarbon seeps in the Gulf of Mexico. Like all vestimentiferans, L. luymesi obtains its nutrition from sulfide-oxidizing endosymbiotic bacteria, which it houses in an internal organ called the trophosome. This tubeworm has a lifespan of over 170 years and its survival is contingent upon the availability of sulfide during this long period. In sediments underlying L. luymesi aggregations, microbes produce sulfide by coupling sulfate reduction with hydrocarbon oxidation. L. luymesi acquires sulfide from the sediment using a root-like posterior extension of its body that is buried in the sediment. Its symbionts then oxidize the sulfide to produce energy for carbon fixation, and release sulfate and hydrogen ions as byproducts. It is critical for the tubeworm to eliminate these waste ions, and it could do so either across its vascular plume or across its root. In this study, we measured sulfate and proton elimination rates from live L. luymesi and found that they eliminated approximately 85% of the sulfate produced by sulfide oxidation, and approximately 67% of the protons produced by various metabolic processes, across their roots. On the basis of experiments using membrane transport inhibitors, we suggest that L. luymesi has anion exchangers that mediate sulfate elimination coupled with bicarbonate uptake. Roots could be the ideal exchange surface for eliminating sulfate and hydrogen ions for two reasons. First, these ions might be eliminated across the root epithelium using facilitated diffusion, which is energetically economical. Second, sulfate and hydrogen ions are substrates for bacterial sulfate reduction, and supplying these ions into the sediment might help ensure a sustained sulfide supply for L. luymesi over its entire lifespan.

Animals↗
PubMed1996

Sulfide may directly modify cytoplasmic hemoglobin deoxygenation in Solemya reidi gills

The clam Solemya reidi, which survives in sulfide-rich sediments, houses intracellular sulfide-oxidizing bacteria as symbionts in its gills. The gill bacteriocytes also contain a high concentration of cytoplasmic hemoglobin. Although the in situ hemoglobin optical spectrum was not altered in the presence of hydrogen sulfide, hemoglobin deoxygenation was significantly slowed and incomplete when sulfide was present. A sulfide-mediated decrease in oxygen consumption rate, a shift in intracellular pH or the conversion of hemoglobin to an unusual derivative could all slow in situ hemoglobin deoxygenation. However, under low sulfide levels at which deoxygenation is incomplete, oxygen consumption rate was not inhibited, intracellular pH decreased by less than 0.1 units and the only hemoglobin derivatives present were deoxyhemoglobin and oxyhemoglobin. These results and preliminary measurements of the isolated gill hemoglobin dissociation rate constants suggest that sulfide or a rapidly formed oxidation product may directly influence the rate of Solemya reidi gill hemoglobin deoxygenation.

Journal Article↗
PubMed2006

Differential targeting of protein kinase B in cell death induced by sulindac and its metabolite sulindac sulfide.

Non-steroidal anti-inflammatory drugs such as sulindac inhibit human colorectal carcinogenesis through a mechanism involving the direct inhibition of cyclooxygenase (Cox)-2. However, a wealth of recent evidence indicates that these agents might elicit their effects through mechanisms independently of Cox-2. In this study, we investigated the effects of sulindac and its metabolite, sulindac sulfide on modulation of the critical survival kinase, protein kinase B (PKB). Here, we demonstrate for the first time that treatment with either sulindac or sulindac sulfide results in a decrease in PKB activity, and we provide compelling evidence that this occurs through two distinct mechanisms. Additionally, we report that overexpression of, and conditional activation of PKB attenuates the apoptotic effects of sulindac, but not for sulindac sulfide - the metabolic metabolite of sulindac. We also demonstrate that treatment with sulindac sulfide, but not sulindac, results in a very early robust activation of both caspase-8 and -9. Furthermore, we show that the apoptotic effects of sulindac sulfide can be reverted by both the caspase-8 and -9 inhibitors. Evidence is provided to indicate that PKB is targeted by robust caspase activation due to sulindac sulfide. Hence, further investigation into the mechanisms regulating conversion of sulindac to sulindac sulfide (or direct use of the latter compound), may enhance our ability to target cancers with enhanced signaling through the growth factor-->phosphatidylinositol 3-kinase pathway.

Adenocarcinoma↗
PubMed1999

Development of an in vitro screening method for evaluating decontamination of sulfur mustard by reactive dermal formulations.

New barrier creams known as topical skin protectants (TSPs) recently have been formulated and demonstrated to be effective in delaying skin penetration of the blistering warfare agent sulfur mustard (HD). To further inactivate or neutralize HD, compounds that react with the toxic agent must be incorporated in the formulations, which then become reactive topical skin protectants (rTSPs). Specific and fast screening methods are necessary to assess the decontaminating activity of rTSPs. A headspace sampling technique in conjunction with thermal desorption and gas chromatography-mass spectrometry was evaluated as a potential screening method. A lower detection limit of 1 ng and a coefficient of variation of <20% were observed for the repetitive measurements of residual HD. Using this method, we evaluated a candidate rTSP. The percentage recovery of HD applied to the rTSP decreased by 35% over a 20-min time period compared with a non-rTSP. The candidate formulation showed an instant decontamination of the HD simulant dibutyl sulfide (decontamination was achieved in 2 s). The instrument set-up has the potential to accommodate multiple samples and can be automated. The method can be extended also to test reactive dermal formulations with toxic organophosphorus compounds.

Administration, Topical↗
PubMed2002

Effect of particle-particle shearing on the bioleaching of sulfide minerals.

The biological leaching of sulfide minerals, used for the production of gold, copper, zinc, cobalt, and other metals, is very often carried out in slurry bioreactors, where the shearing between sulfide particles is intensive. In order to be able to improve the efficiency of the bioleaching, it is of significant importance to know the effect of particle shearing on the rate of leaching. The recently proposed concept of ore immobilization allowed us to study the effect of particle shearing on the rate of sulfide (pyrite) leaching by Thiobacillus ferrooxidans. Using this concept, we designed two very similar bioreactors, the main difference between which was the presence and absence of particle-particle shearing. It was shown that when the oxygen mass transfer was not the rate-limiting step, the rate of bioleaching in the frictionless bioreactor was 2.5 times higher than that in a bioreactor with particle friction (shearing). The concentration of free suspended cells in the frictionless bioreactor was by orders of magnitude lower than that in the frictional bioreactor, which showed that particle friction strongly reduces the microbial attachment to sulfide surface, which, in turn, reduces the rate of bioleaching. Surprisingly, it was found that formation of a layer of insoluble iron salts on the surface of sulfide particles is much slower under shearless conditions than in the presence of particle-particle shearing. This was explained by the effect of particle friction on liquid-solid mass transfer rate. The results of this study show that reduction of the particle friction during bioleaching of sulfide minerals can bring important advantages not only by increasing significantly the bioleaching rate, but also by increasing the rate of gas-liquid oxygen mass transfer, reducing the formation of iron precipitates and reducing the energy consumption. One of the efficient methods for reduction of particle friction is ore immobilization in a porous matrix.

Bioreactors↗
PubMed2003

Effect of nitrite and nitrate on in situ sulfide production in an activated sludge immobilized agar gel film as determined by use of microelectrodes.

Microelectrode, fluorescence in situ hybridization (FISH), and denaturing gradient gel electrophoresis (DGGE) analyses were used to investigate the effect of nitrite and nitrate on in situ sulfide production in an activated sludge immobilized agar gel film. Microelectrode measurements of O(2), H(2)S, NO(3)(-), NO(2)(-), and pH revealed that the addition of NO(2)(-) and NO(3)(-) forced sulfate reduction zones deeper in the agar gel and significantly reduced the in situ sulfide production levels. The sulfate reduction zone was consequently separated from O(2) and NO(2)(-) or NO(3)(-) respiration zones with increasing the concentrations of NO(2)(-) and NO(3)(-). These NO(2)(-) and NO(3)(-) treatments had only a transient effect on sulfide production. The in situ sulfide production quickly recovered to the previous levels when NO(2)(-) and NO(3)(-) were removed. The PCR-DGGE and FISH analyses revealed that 2-day-continuous addition of 500 microM NO(3)(-) did not change the metabolically active sulfate-reducing bacterial (SRB) community. On the basis of these data, it could be concluded that the addition of NO(2)(-) and NO(3)(-) did not kill SRB, but induced the interspecies competition for common carbon source (i.e., acetate) between nitrate-reducing heterotrophic bacteria and SRB and enhanced the oxidation of the produced sulfide, which were main possible causes of the suppression of in situ sulfide production in the agar gel.

Agar↗
PubMed2006

Tandem mass spectra of divalent metal ion adducts of glycosyl sulfides, sulfoxides and sulfones; distinction among stereoisomers.

The tandem mass spectra of the divalent metal ion (Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Ni2+, Co2+ and Zn2+) adducts of acetylated 1,2-trans-glycosyl sulfides, sulfoxides and sulfones were examined using low energy collision-induced dissociation on a Quattro II quadrupole tandem mass spectrometer. Abundant doubly charged ions, such as [3M + Met]2+ and [2M + Met]2+, were observed with alkaline earth metal chlorides. The other ions observed were [M + MetCl]+, [M + MetOAc]+, [M + MetO2SPh]+ and [2M + MetCl]+. The deprotonated metal adducts [M + Met-H]+ were seen only in the sulfones. The divalent metal ion adducts showed characteristic fragmentation pathways for the glycosyl sulfides, sulfoxides and sulfones, depending on the site of metal attachment. The doubly charged metal ion adducts dissociate to two singly charged ions, [M + MetOAc]+ and [M - OAc]+, in the sulfides and sulfoxides. In the sulfones, the adducts dissociate to [M + MetO2SPh]+ and [M - O2SPh]+. In contrast to the alkaline earth metals, which attach to the acetoxy functions, the transition metals attach to the sulfide and sulfoxide functions. The metal chloride adducts display characteristic fragmentation for the sulfides, sulfoxides and sulfones. The glucosyl, mannosyl and galactosyl sulfides, sulfoxides and sulfones could be differentiated on the basis of the stereochemically controlled MS/MS fragmentations of the metal chloride adducts.

Chlorides↗
PubMed2002

Inhibition of sulfate-reducing bacteria by metal sulfide formation in bioremediation of acid mine drainage.

Acid mine drainage (AMD) containing high concentrations of sulfate and heavy metal ions can be treated by biological sulfate reduction. It has been reported that the effect of heavy metals on sulfate-reducing bacteria (SRB) can be stimulatory at lower concentrations and toxic/inhibitory at higher concentrations. The quantification of the toxic/inhibitory effect of dissolved heavy metals is critical for the design and operation of an effective AMD bioremediation process. Serum bottle and batch reactor studies on metal toxicity to SRB indicate that insoluble metal sulfides can inhibit the SRB activity as well. The mechanism of inhibition is postulated to be external to the bacterial cell. The experimental data indicate that the metal sulfides formed due to the reaction between the dissolved metal and biogenic sulfide act as barriers preventing the access of the reactants (sulfate, organic matter) to the necessary enzymes. Scanning electron micrographs of the SRB cultures exposed to copper and zinc provide supporting evidence for this hypothesis. The SRB cultures retained their ability to effect sulfate reduction indicating that the metal sulfides were not lethally toxic to the SRB. This phenomenon of metal sulfide inhibition of the SRB has to be taken into account while designing a sulfate-reducing bioreator, and subsequently an efficient biotreatment strategy for AMD. Any metal sulfide formed in the bioreactor needs to be removed immediately from the system to maintain the efficiency of the process of sulfate reduction.

Biodegradation, Environmental↗
PubMed1988

Sulfide silver amplification of ferritin iron cores in blood and bone marrow cells. Methods, adaptations to microphysical analyses, and the impact of advanced iron overload.

A short exposure of cell suspensions to gaseous hydrogen sulfide, appropriate fixations, and subsequent physical development of silver shells around sulfidated insoluble metals were used to amplify ferritin iron cores in blood and bone marrow cells. The methods described are suitable for both light microscopy and transmission electron microscopy. These techniques made it possible to visualize Prussian Blue stainable ferritin and haemosiderin, as well as a large variety of isoferritin iron and other smaller particles beyond the sensitivity of Prussian Blue staining. Admixtures of sulfidatible zinc and traces of other heavy metals had to be taken into consideration. For further research, adaptations of sulfide silver staining to microphysical analyses were developed. However, conventional energy dispersive X-ray analysis was not sensitive enough to signalize the presence of Fe in sulfide silver amplified iron cores of a single or a few ferritin molecule(s). Proton-induced X-ray emission was used to measure Fe and Zn down to 1 fg/single cell in unstained or sulfide silver stained smears on thin foils. However, multielement analysis of homogeneous cell concentrates was much easier to perform and far more sensitive. In advanced iron overload, highly increased sulfide silver staining was found in peripheral blood cells including lymphocytes, monocytes, eosinophils, basophils, and--in extreme cases--also in neutrophils and platelets.

Blood Cells↗
PubMed1995

Energy-dispersive X-ray analysis of the extracellular cadmium sulfide crystallites of Klebsiella aerogenes.

Klebsiella aerogenes forms electron-dense particles on the cell surface in response to the presence of cadmium ions in the growth medium. These particles ranged from 20 to 200 nm in size, and quantitative energy dispersive X-ray analysis established that they comprise cadmium and sulfur in a 1:1 ratio. This observation leads to the conclusion that the particles are cadmium sulfide crystallites. A combination of atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, and acid-labile sulfide analysis revealed that the total intracellular and bound extracellular cadmium:sulfur ratio is also 1:1, which suggests tha the bulk of the cadmium is fixed as extracellular cadmium sulfide. The tolerance of K. aerogenes to cadmium ions and the formation of the cadmium sulfide crystallites were dependent on the buffer composition of the growth medium. The addition of cadmium ions to phosphate-buffered media resulted in cadmium phosphate precipitates that remove the potentially toxic cadmium ions from the growth medium. Electron-dense particles formed on the surfaces of bacteria grown under these conditions were a combination of cadmium sulfide and cadmium phosphates. The specific bacterial growth rate in the exponential phase of batch cultures was not affected by up to 2mM cadmium in Tricine-buffered medium, but formation of cadmium sulfide crystallites was maximal during the stationary phase of batch culture. Cadmium tolerance was much lower (10 to 150 microM) in growth media buffered with Tris, Bistris propane, Bes, Tes, or Hepes. These results illustrate the importance of considering medium composition when comparing levels of bacterial cadmium tolerance.

Cadmium↗
PubMed2001

Aerobic sulfide production and cadmium precipitation by Escherichia coli expressing the Treponema denticola cysteine desulfhydrase gene.

The cysteine desulfhydrase gene of Treponema denticola was over-expressed in Escherichia coli to produce sulfide under aerobic conditions and to precipitate metal sulfide complexes on the cell wall. When grown in a defined salts medium supplemented with cadmium and cysteine, E. coli producing cysteine desulfhydrase secreted sulfide and removed nearly all of the cadmium from solution after 48 h. A control strain produced significantly less sulfide and removed significantly less cadmium. Measurement of acid-labile sulfide and energy dispersive X-ray spectroscopy indicated that cadmium was precipitated as cadmium sulfide. Without supplemental cysteine, both the E. coli producing cysteine desulfhydrase and the control E. coli demonstrated minimal cadmium removal.

Aerobiosis↗