Team:SCUT-China A/Project Overview




        SCUT-China_A team tries to build a group of heavy metal detecting devices: We standardized the lysis gene SRRz to build a visible and low-cost reporter which can detect chemical substances qualitatively. And it can also detect chemical substances quantitatively in a certain concentration range. Subsequently, we will link some specific inducible promoters of heavy metal ions to the reporter and transform these devices into Escherichia coli BL21 to verify the feasibility of the reporter and construct engineering bacteria that can rapidly detect heavy metal ions in water.

1. The current situation of the heavy metal pollution

        With the expansion of the city and the development of large-scale industries, heavy metal pollution in the environment has become a serious social problem. More heavy metal ions are discharged into the water through mining, metal smelting, the wastewater of chemical industry, and other anthropogenic sources. Most heavy metals ions are toxic to humans at even micro-concentration. As they are toxic, and can be biologically enriched, they severely threaten the safety and health of humans.
        However, the current methods of heavy metal ions detection are complex and expensive.

2. Current detection methods of the heavy metal

2.1 Chemical methods
         Nowadays, the major detection methods of heavy metal ions are ICP-AES, ICP-MS, AAFS, GHAAS. The advantages of these methods are low detection limit and high specificity, but they require expensive instruments and complex operation, which is relatively unavailable for the non - professional, and it cannot detect the bioavailability of heavy metals.

2.2 Biosensor based on traditional reporter
        In the past few years, some projects developed biosensors to detect heavy metal ions, most of which selected GFP as the reporter. The advantages of biosensors based on GFP is low-cost, and the expression of GFP can be directly measured by a certain method. However, the response of GFP usually spends 2-3 hours. And the measurement of fluorescent proteins requires spectrophotometers which is expensive and requires professional operations.
        Therefore, we set a goal to design a more efficient report module, and build up a series of heavy metal detecting module that can efficiently and highly selectively detect heavy metal ions in aqueous solutions.

Design of our project

        To sort this problem, our team tries to develop a novel method to detect heavy metal ions, which could measure the metal ions in the aqueous solution specificity and efficiently with low cost.
        By the release of neurotransmitter, we used the lysis gene SRRz (BBa_K2360000) from the phage together with the endogenous enzyme β-galactosidase as a report module, which can efficiently respond to specific signal. The development of this module might sort out the problem—long respond time of traditional report module—GFP. What’s more, we chose the specific heavy metal ions operons to build up our detecting modules to achieve the specific detection of our method.
        The method we developed inherited the characteristics of previous biosensors: low cost and relatively convinient. Moreover, it enhances its response speed and simplifying the measurement method, providing a new mean for the public to detect heavy metal ions in the environment around them conveniently and efficiently.

Figure 1. gene circuit of the project

        According to the previous researches, we found that the depth of the color produced by the chromogenic reaction is positively correlated to the lysis rate of the cells, and the lysis rate of the cells is positively correlated to the intensity of the SRRz, which is induced by its operon, and finally determined by the intensity of the heavy metal ions. This result made it able to be used for not only qualitative detection but also quantitative measurement.

Results & Demonstration
Detect& Lysis

        We successfully developed three specific detecting devices and achieved our idea. By imitating the release of neurotransmitters, the effect of our report module is very significant. Our devices can detect heavy metal ions and make remarkable response in one hour. Figure 2 is one of our response effect.


        Based on the principles mentioned above, we developed a smart phone app to optimize our method of quantitative measurement. People can use our devices to qualitatively detect whether there are heavy metal ions in the solution, and use their cell phone to scan the samples after the chromogenic reaction to quantitatively measure the concentration of the ions.


        We take water samples from water sources near metalworking plants, and demonstrate our products in the samples.

Potential applications

        Besides detecting heavy metal ions, our report module can also be used in various fields of detection. By combining with different detection modules to our report module, other components could also be detected. For example, a combination of a detection module that responds to aflatoxin and our reporter module can be used to rapidly detect aflatoxin.
         Therefore, our report module could be applied to build up efficient and low-cost biosensors which would make biosensors be widely used in various detecting field.


[1]. Fu Jing, The Research of Electrochemical Sensors for Heavy Metals Monitoring in Water Environment. Dissertation submitted to Zhejiang University for the degree of Master of Engineering.Page1.
[2]. Magrisso S, Erel Y, Belkin S. Microbial reporters of metal bioavailability [J]. Microbial Biotechnology, 2008, 1(4) : 320-330
[3]. Leveau J H, Lindow S E. Predictive and interpretive simulation of green fluorescent protein expression in reporter bacteria [J]. Journal of Bacteriology, 2001, 183(23):6752.