Engineered Escherichia coli silver-binding periplasmic protein that promotes silver tolerance

Area of Science:

• Microbiology
• Biotechnology
• Materials Science

Background:

• Microorganisms encounter silver toxicity in medical and environmental contexts.
• Bacterial adaptation to silver ions can lead to pathogenic strains or useful applications in nanomaterial manufacturing.
• Naturally adapted bacteria often use efflux pumps for metal resistance.

Purpose of the Study:

• To engineer a silver-tolerant Escherichia coli strain using a novel peptide-based approach.
• To investigate the potential of a specific silver-binding peptide (AgBP2) for conferring metal tolerance.
• To explore new methods for manipulating bacterial interactions with heavy metals.

Main Methods:

• Identification of a silver-binding peptide (AgBP2) from a combinatorial display library.
• Fusion of AgBP2 to the maltose-binding protein (MBP) of E. coli.
• Growth experiments with silver nitrate to assess silver tolerance in engineered E. coli strains.
• Transmission electron microscopy to analyze silver nanoparticle formation.

Main Results:

• Engineered E. coli secreting MBP-AgBP2 into the periplasm showed significant silver tolerance.
• Cytoplasmic expression of the fusion protein or MBP alone did not confer silver tolerance.
• Transmission electron microscopy revealed electron-dense silver nanoparticles in tolerant cells.
• Demonstrated nanomolar affinity of the engineered protein for silver ions.

Conclusions:

• A specifically engineered metal-binding peptide can confer a strong in vivo phenotype for silver tolerance.
• Short, simple peptide motifs offer a novel way to manipulate bacterial interactions with heavy metals.
• Engineered metal-ion-tolerant microorganisms have potential applications in remediation and in vivo biomolecule-metal interaction studies.