Recombinant Bacillus amyloliquefaciens Cadmium, cobalt and zinc/H (+)-K (+) antiporter
Description
Functional Role in Heavy Metal Resistance
Comparative genomic analyses of B. amyloliquefaciens strains (e.g., Bam1 and FZB42) highlight CzcD's contribution to metal tolerance:
| Strain | Metal Resistance Profile (MIC, µg/mL) | Key Genes Involved |
|---|---|---|
| Bam1 | Cd²⁺: 512; Zn²⁺: 1024; Co²⁺: 256 | czcD, cadA |
| FZB42 | Cd²⁺: 64; Zn²⁺: 256; Co²⁺: 64 | czcD (lower activity) |
Key Findings:
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Cadmium resistance: Deletion of czcD in strain Bam1 reduced Cd²⁺ MIC by 16-fold, underscoring its role in Cd²⁺ efflux .
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Zinc and cobalt: CzcD works synergistically with CadA (a P-type ATPase) to export Zn²⁺ and Co²⁺, particularly under high metal concentrations .
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Non-essential metals: CzcD also mitigates toxicity from non-essential metals like Pb²⁺ through non-specific export .
Genomic Context
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DNA islands: czcD is located within genomic islands in B. amyloliquefaciens Bam1, flanked by mobile genetic elements that enhance horizontal gene transfer .
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Prophage associations: Unlike strain FZB42, Bam1 retains prophage regions encoding auxiliary metal-resistance genes .
Expression Profiles
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Induction under stress: Transcriptomic data show czcD upregulation by 12-fold under Cd²⁺ stress, compared to 3-fold in Zn²⁺-exposed cells .
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Regulatory interplay: CzcD expression is modulated by Fur (for Fe²⁺ homeostasis) and Zur (for Zn²⁺ regulation) .
Biotechnological Applications
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Bioremediation: Recombinant B. amyloliquefaciens strains overexpressing CzcD demonstrate enhanced Cd²⁺ removal from contaminated soils (up to 80% efficiency in lab-scale trials) .
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Agricultural use: Engineered strains improve plant growth under heavy metal stress by reducing metal uptake in rhizospheres .
Comparative Analysis with Homologs
| Feature | B. amyloliquefaciens CzcD | B. subtilis CzcD |
|---|---|---|
| Substrate range | Cd²⁺, Co²⁺, Zn²⁺ | Zn²⁺, Co²⁺ |
| Regulatory mechanism | CzrA-dependent | ArsR-dependent |
| Metal affinity (Kd) | Cd²⁺: 0.2 µM | Zn²⁺: 0.5 µM |
Note: B. amyloliquefaciens CzcD exhibits broader substrate specificity and higher Cd²⁺ affinity than homologs in related species .
Challenges and Future Directions
Product Specs
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Target Background
This protein is involved in divalent cation and potassium homeostasis within cells. It catalyzes the active efflux of zinc, cadmium, and cobalt in exchange for potassium and H+ ions.
KEGG: bay:RBAM_005600
