P-cresol (p-Cresol) is a kind of organic compound, its chemical formula is C7H8O, it is a kind of harmful substance, it can cause skin irritation, respiratory tract irritation and other adverse reactions, and even affect the production of organs such as central nervous system and liver.

The following table shows the possible human harm caused by cresol.

At present, traditional chemical and physical methods are mainly used to monitor p-cresol in factories, such as spectral analysis, gas chromatography, high performance liquid chromatography and so on. Although these methods can accurately measure the concentration of p-cresol, they have some disadvantages:

Therefore, although these methods can provide factories with important information about p-cresol pollution, many factories choose not to monitor cresol due to cost, time and operational constraints.

In order to solve these problems, the new biosensor has become a promising technology choice. The biosensor can be detected by using the high sensitivity and specificity of biomolecules, and it has the advantages of low cost and easy operation, so it is suitable for on-site rapid monitoring and continuous real-time monitoring. By applying biosensor technology to factory environmental monitoring, we are expected to deal with the challenge of p-cresol pollution more effectively and protect the health of workers and the sustainable development of the environment.

The gene circuit diagram of our project is shown above.

In the circuit, we first designed a chromogenic module, which is composed of promoter, RBS, tyrosinase gene and Terminator. Tyrosinase gene is transcribed and translated into tyrosinase. Tyrosinase can convert p-cresol into 4-methylcatechol and then into 4-methyl-o-quinone. When exogenous MBTH is added, 4-methyl-o-quinone reacts with it, and the reaction product will quickly become another pink compound, which can be observed.

Then, we designed a cleavage module, which is composed of arabinose promoter, RBS, SRRz cleavage gene and Terminator. Among them, the SRRz cleavage gene is transcribed and translated into three lyases, which can change the membrane permeability, degrade the cell wall and release the cell contents. Our SRRz cleavage gene is a linked gene composed of perforin gene S, phage lysozyme gene R and gene RZ. The product of R gene is the soluble transglycosylase, which decomposes the peptidoglycan in the cell wall. The product of RZ gene is endopeptidase, which cleaves between oligosaccharides of peptidoglycan and crosslink between peptidoglycan and outer membrane of cell wall. The effect of S gene product is to change the permeability of the plasma membrane.The formation of a porous structure enables the enzymes produced by R and RZ genes to cross the plasma membrane to the cell wall, breaking the cell wall and releasing substances in the cell. The function of R and RZ gene products is to degrade the cell wall.

The sensing principle for the arabinose promoter is as follows: when there is no arabinose in the environment, the promoter does not activate the downstream gene circuit, and when there is arabinose in the environment, the promoter initiates the downstream transcription and translation of the cleavage gene, and then releases the intracellular tyrosinase into the environment to produce a chromogenic reaction.

In other words, when we add MBTH and arabinose, when the solution is colorless, it proves that there is no p-cresol in the environment, when the solution is pink, it proves that there is p-cresol in the environment, and the darker the color, the higher the concentration of p-cresol.

From beginning to end, our target users are workers in chemical production plants, and chemicals are more or less harmful to health, so we focus on such groups. We have interviewed scholars in related research fields and made very good progress. Scholars suggest that workers who have suffered from related diseases, those who are suffering from diseases, or those who have just joined the workforce will be more eager to monitor the concentration of p-cresol in the environment.

The specific process of introducing the p-cresol sensor we designed into environmental monitoring is as follows:

1. The engineering bacteria were placed in liquid medium and cultured for a period of time to activate the strain and express tyrosinase.

2. Such as adding liquid or gas to liquid medium.

3. MBTH and arabinose were added to induce the expression of SRRz cleavage gene and cleavage bacteria.

4. The content of p-cresol is judged by observing whether the solution turns pink and the depth of pink.

In order to prevent the spread of engineering bacteria into the natural environment and cause pollution, we add SRRz cleavage gene to the genetic circuit. when we add arabinose, the arabinose promoter will start the transcription and translation of SRRz, and the three lyases produced by SRRz can break the cell membrane and cell wall of the engineering bacteria, thus releasing the inclusions. this step will also kill the bacteria, thus ensuring that no engineering bacteria are released.

In this paper, a kind of p-cresol sensor is designed to monitor the concentration of p-cresol in the environment, which is of great significance to ensure the health and safety of cresol.

1. The substance sensor enables the separation of substances with specific reactivity to detect the existence and concentration of the standard score.

For the pollution of p-cresol in the environment, the substance sensor can warn and prevent the potential danger by detecting the presence and concentration of p-cresol. For example, if the concentration of p-cresol exceeds the safety limit, the sensor can notify managers in time through alarms or "turn off the machine" so that they can take the necessary measures to reduce the concentration of pollutants.

2. This p-cresol substance sensor can help birds better understand their working environment and provide timely warning and protection to make them safer when working.

The development of material sensors can also promote the research and monitoring of pollutants in the environment, and contribute to environmental protection and sustainable development. Therefore, the design of p-cresol sensor is of great significance for protecting the health and promoting the sustainable development of the environment.

In general, the p-cresol sensor we designed makes it convenient and easy to operate, can quickly and accurately detect the concentration of p-cresol in the environment, helps to improve the health and safety of cresol, and embodies the idea of environmental protection innovation. to contribute to the sustainable development of the environment.

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