Glutathione-mediated cadmium sequestration in Rhizobium leguminosarum

Lima, Ana; Corticeiro, Sofia; Figueira, Etelvina

doi:10.1016/j.enzmictec.2005.12.009

Cited by 100 publications

(22 citation statements)

References 33 publications

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“…Because no reliable methods for nanoparticle quantification are currently available, the amounts of intracellular CdS were indirectly quantified by ICP at different time postaddition as described. 12,20 Figure 4b confirms that the amount of intracellular CdS in all groups increased steadily with time. Strikingly, the recombinant cells produced significantly more (P \ 0.05) CdS than the wild-type cells at as early as 20 min, at which time 10 mM IPTG resulted in the highest CdS production.…”

Section: Enhanced Synthesis Of Gsh and Cds Nanoparticles In The Cellssupporting

confidence: 86%

Augmented biosynthesis of cadmium sulfide nanoparticles by genetically engineered Escherichia coli

Chen

Tuan

Tien

et al. 2009

Biotechnology Progress

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Microorganisms can complex and sequester heavy metals, rendering them promising living factories for nanoparticle production. Glutathione (GSH) is pivotal in cadmium sulfide (CdS) nanoparticle formation in yeasts and its synthesis necessitates two enzymes: gamma-glutamylcysteine synthetase (gamma-GCS) and glutathione synthetase (GS). Hereby, we constructed two recombinant E. coli ABLE C strains to over-express either gamma-GCS or GS and found that gamma-GCS over-expression resulted in inclusion body formation and impaired cell physiology, whereas GS over-expression yielded abundant soluble proteins and barely impeded cell growth. Upon exposure of the recombinant cells to cadmium chloride and sodium sulfide, GS over-expression augmented GSH synthesis and ameliorated CdS nanoparticles formation. The resultant CdS nanoparticles resembled those from the wild-type cells in size (2-5 nm) and wurtzite structures, yet differed in dispersibility and elemental composition. The maximum particle yield attained in the recombinant E. coli was approximately 2.5 times that attained in the wild-type cells and considerably exceeded that achieved in yeasts. These data implicated the potential of genetic engineering approach to enhancing CdS nanoparticle biosynthesis in bacteria. Additionally, E. coli-based biosynthesis offers a more energy-efficient and eco-friendly method as opposed to chemical processes requiring high temperature and toxic solvents.

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Section: Enhanced Synthesis Of Gsh and Cds Nanoparticles In The Cellssupporting

confidence: 86%

Augmented biosynthesis of cadmium sulfide nanoparticles by genetically engineered Escherichia coli

Chen

Tuan

Tien

et al. 2009

Biotechnology Progress

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“…The fact that Cd was mainly found in the tightly bound fraction, corresponding to cell wall, suggests that retention in this compartment could be reducing intracellular Cd concentration being an important avoidance mechanism acting like a primary defense system. Lima et al (2006) and Siñeriz Louis et al (2009) demonstrated that the highest Cd concentration was found in the cell wall of Rhizobium leguminosarum biovar viciae and Streptomyces sp. F4, respectively.…”

Section: Discussionmentioning

confidence: 96%

Involvement of glutathione and enzymatic defense system against cadmium toxicity in Bradyrhizobium sp. strains (peanut symbionts)

2011

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In this study, the effects of cadmium (Cd) on cell morphology and antioxidant enzyme activities as well as the distribution of the metal in different cell compartments in Bradyrhizobium sp. strains were investigated. These strains were previously classified as sensitive (Bradyrhizobium sp. SEMIA 6144) and tolerant (Bradyrhizobium sp. NLH25) to Cd. Transmission electron micrographs showed large electron-translucent inclusions in the sensitive strain and electron-dense bodies in the tolerant strain, when exposed to Cd. Analysis of Cd distribution revealed that it was mainly bounded to cell wall in both strains. Antioxidant enzyme activities were significantly different in each strain. Only the tolerant strain was able to maintain a glutathione/oxidized glutathione (GSH/GSSG) ratio by an increase of GSH reductase (GR) and GSH peroxidase (GPX) enzyme activities. GSH S-transferase (GST) and catalase (CAT) activities were drastically inhibited in both strains while superoxide dismutase (SOD) showed a significant decrease only in the sensitive strain. In conclusion, our findings suggest that GSH content and its related enzymes are involved in the Bradyrhizobium sp. tolerance to Cd contributing to the cellular redox balance.

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“…In contrast, not much is known about the interplay of heavy metals and GSH in bacteria, except that GSH influences resistance to arsenite and mercury in E. coli (32) and cadmium tolerance in Rhizobium leguminosarum bv. viciae (15,35). On the other hand, GSH is heavily involved in transition-metal homeostasis in eukaryotes.…”

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confidence: 99%

Glutathione and Transition-Metal Homeostasis inEscherichia coli

et al. 2008

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Glutathione (GSH) and its derivative phytochelatin are important binding factors in transition-metal homeostasis in many eukaryotes. Here, we demonstrate that GSH is also involved in chromate, Zn(II), Cd(II), and Cu(II) homeostasis and resistance in Escherichia coli. While the loss of the ability to synthesize GSH influenced metal tolerance in wild-type cells only slightly, GSH was important for residual metal resistance in cells without metal efflux systems. In mutant cells without the P-type ATPase ZntA, the additional deletion of the GSH biosynthesis system led to a strong decrease in resistance to Cd(II) and Zn(II). Likewise, in mutant cells without the P-type ATPase CopA, the removal of GSH led to a strong decrease of Cu(II) resistance. The precursor of GSH, ␥-glutamylcysteine (␥EC), was not able to compensate for a lack of GSH. On the contrary, ␥EC-containing cells were less copper and cadmium tolerant than cells that contained neither ␥EC nor GSH. Thus, GSH may play an important role in trace-element metabolism not only in higher organisms but also in bacteria.Under aerobic growth conditions, either glutathione (GSH; L-␥-glutamyl-L-cysteine-glycine) or the small 12-kDa protein thioredoxin (TrxB) is essential to maintain a reduced environment in the cytosol of Escherichia coli cells (5,27,60,65). Since E. coli thioredoxin reductase can transfer electrons from NADH to glutaredoxin 4 (Grx4, GrxD, or YdhD) and Grx4 can reduce Grx1 (GrxA) and Grx3 (GrxC) (14), E. coli is able to catalyze the reduction of disulfides without GSH. Thus, GSH by itself is not essential for the survival of this bacterium (17).The cellular GSH is kept almost completely reduced (2, 30): the reduced GSH-oxidized GSH (GSSG) couple has a standard redox potential at pH 7.0 of Ϫ240 mV (66). Using a potential of about Ϫ260 mV in vivo (29) and the Nernst equation results in the calculation of a GSH concentration of about 5 mM and a GSSG concentration of about 5 M. Therefore, any change in the GSH concentration is likely to influence the cellular metabolism by changing the redox potential of the cytoplasm and maybe also that of the periplasm (59). A decrease of the GSH concentration by half would increase the cytoplasmic redox potential by 18 mV.GSH is also involved in the osmoadaptation of E. coli (39). As a response to highly osmotic conditions, a mutant strain unable to synthesize trehalose as an osmoprotectant accumulates GSH to a concentration about 10-fold that under normal conditions. The first and quickest response of E. coli to changing osmotic conditions is to change the cytoplasmic potassium concentration (39), and indeed, GSH is needed for the regulation of this pool (13), probably through interaction with the GSH-gated potassium efflux system KefCYabF (43). Moreover, GSH is involved in the detoxification of methylglyoxal (13), although there are GSH-independent pathways of methylglyoxal degradation (44), and resistance to chlorine compounds (7, 67). In bacteria other than E. coli, GSH is essential for thiamine synthesis (19) and ...

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Glutathione-mediated cadmium sequestration in Rhizobium leguminosarum

Cited by 100 publications

References 33 publications

Augmented biosynthesis of cadmium sulfide nanoparticles by genetically engineered Escherichia coli

Augmented biosynthesis of cadmium sulfide nanoparticles by genetically engineered Escherichia coli

Involvement of glutathione and enzymatic defense system against cadmium toxicity in Bradyrhizobium sp. strains (peanut symbionts)

Glutathione and Transition-Metal Homeostasis inEscherichia coli

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