Overview

In this study, we contributed 8 new parts to iGEM, including 4 basic parts and 4 composite parts. Using these 8 new parts, along with 5 previously existing basic parts, we successfully engineered an E. coli reporter strain based on the pET28a-chr-T7-amilCP biosensor using synthetic biology techniques. The protein encoded by the chrB gene in this strain participates in the bacterial resistance mechanism against chromate, enabling a specific response to hexavalent chromium [Cr(VI)] in the environment and assisting the bacteria in counteracting its toxic stress. This protein exhibits high specificity for Cr(VI) reduction, making it a core component for constructing Cr(VI) biosensors. When the reporter strain encounters Cr(VI)-containing samples, the chrB gene is activated, initiating downstream reactions that drive the expression of the pigment protein amylocysteinyl-coenzyme P (amilCP). This results in a visible blue-violet phenotype, enabling the visual detection of Cr(VI).

Building upon this, we further engineered a soluble flavoprotein system for efficient expression in Escherichia coli BL21(DE3), aiming to maximize the reduction of highly toxic Cr(VI) in chromium-contaminated wastewater to less toxic trivalent chromium [Cr(III)]. Compared to traditional chemical precipitation and physical adsorption methods, this microbial remediation strategy offers advantages such as low cost, ease of operation, and environmental friendliness. It effectively avoids secondary pollution, providing a sustainable biotechnological solution for industrial chromium pollution control.

The relevant parts are listed in Table 1. Among them, the first five (BBa_K3521000, BBa_K592009, BBa_K3521004, BBa_K3584001, BBa_K914003) are pre-existing parts, while the others are new parts contributed by this study.

Our team has developed a modular collection of genetic parts for the detection and degradation of hexavalent chromium [Cr(VI)], integrating high efficiency with rapid response. The detection plasmid, pET28a-chr-T7-amilCP, encodes the chromoprotein amilCP, which produces a visible blue color in the presence of Cr(VI), while degradation plasmids based on pSC101 vectors encoding ChrR, YieF, and ChrR-YieF enable effective enzymatic reduction of Cr(VI) into the less toxic trivalent form [Cr(III)]. Although pSC101-YieF proved most effective in tolerating and degrading Cr(VI), we explored both single-enzyme and fusion-enzyme strategies to optimize catalytic performance. The compatibility of these parts allows detection and degradation microbes to be paired seamlessly—demonstrated in our hardware device—to achieve accurate sensing and rapid detoxification in a unified workflow. Our repeated testing also indicates that these microbes perform with high responsiveness and efficiency, suggesting their potential scalability for real-world applications in bioremediation. These qualities—modularity, robustness, and demonstrated effectiveness—are hence why we are applying for the Parts Collection Special Prize.

Table 1. The relevant parts