The water-quality heavy metal detector is widely used in electric power, the chemical industry, petroleum, papermaking, printing and dyeing, coal, metallurgy, environmental monitoring, food hygiene, tap water, hydrogeology, and other fields. Water quality heavy metal detector is suitable for the concentration of heavy metals such as trivalent chromium, hexavalent chromium, magnesium, phosphorus, ammonia, nitrogen, chlorine, cobalt, zinc, potassium, copper, silver, molybdenum, cadmium, nickel, and iron in distilled water, drinking water, domestic water, surface water and treated wastewater.

Water quality heavy metal detector, used to analyze the content of heavy metal components of water quality professional instrument, in order to protect the water environment, must strengthen the monitoring of sewage discharge, the quality detector in environmental protection, water quality detection, and water resources protection has played an important role.

According to the recent data obtained from Puhua Official Website, the market size of heavy metal detection equipment for water quality in China has been on a growing trend from 2016 to 2019, with an average annual growth rate of about 15%.

Analysis of water quality heavy metal detector industry market size from 2016 to 2019

From this chart, we can find that the public has a great demand for heavy metal sensors, so we have more confidence and courage to design a microbial sensor to detect the concentration of heavy metal ions.

Before we conduct social sampling activities, we will explain our project, so that people can understand what we do and find out our problems better. We introduced the operation and rules of our project in the offline assembly and shared the project and problems with other teams of iGEM and professional professors of synthetic biology or biology in the online assembly.

In addition to the speech, we will also introduce our project and experimental details on the three-folds and propagandas, and leave the official contact information of our team, so that you can ask us questions or put forward constructive suggestions.

In the early stage of the survey and experiment, we plan to collect public opinions on the use of microorganisms through questionnaires, interviews, and other ways. The questionnaire asked about recent microbial applications in different aspects, such as synthetic biology and pollution resolution.

The questionnaire included a total of 474 responses from people of all ages, genders, and educational levels, including most of the diversity of the results.

In our questionnaire, we can find out the results of a total of 1262 answers to the question "What substances do you think are toxic to the human body in your cognitive range", 54.20% of them are mercury and lead. However, zinc and copper, which are also important elements of heavy metal pollution, were selected the least after the "not known" and "other" options, only 12.04% and 6.18%, respectively. Such a large multiple difference makes us all the more eager to analyze the reasons behind this unusual result.

Most people believe that mercury and lead are harmful to human health. Because these two substances teach people from an early age. Mercury is a component of mercury, which is present in thermometers, and thermometers are broken and need to be kept away from the mercury. Lead poisoning is mostly caused by pencils. When they are young, they are often told not to bite pencils or they will get lead poisoning.

Because mercury and lead are more present in people's lives, most people think that mercury and lead can cause poisoning. But there is little public awareness of copper and zinc pollution, so copper and zinc are more likely to affect people's lives in a subtle way. So we must focus on copper and zinc pollution and find ways to detect and prevent it.

In the question "Which of the following do you think best describes your perception of heavy metal pollution?", we found that people's perception of the impact of heavy metal pollution mostly exists in the impact on crops and industrial slag removal. These are closer to people's lives, so we can take these pollution sources as our solution target, from the closest to everyone to solve the beginning, in order to achieve better results.

The early stage of the experiment was carried out on the project, using the carbon column as a battery, but after many experiments found that currently said the relatively small number, is not easy to observe, suggesting that the carbon column is not suitable for use as an electrode.

We discussed the problem in a meeting with other teams and with a professor called Jiequn Wu, and the results were: carbon column and solution of the contact area is too small, coupled with e. coli is difficult to adhere to the above, once electron transfer out of e. coli, Electronic will move to the anode of the battery, to generate an electric current change, to improve the resolution, replace carbon pillars with electrode carbon felt, because of the electrode carbon felt more contact area and e. coli are more easily attached, so contact electronic increase, increase in the number of electrons moving in the wire, thereby increasing current, currently said number increase, easier to observe, and experiment in the comparison.

At the same time, the experiment on this project showed that the current changes were not obvious, which could indicate that the electron transfer efficiency of E. coli oxidation was low, and the electron was also transferred out.

We tell this finding to AP Biology Teacher Tianfeng Li, who was a professional biology major, and asked whether there was any way to solve or improve the situation. Professor Li Tianfeng suggested that the problem could be solved by using Advanced Placement courses learned in high school. We can solve these problems by simply using PCR to add genes to our experimental vector organisms that enhance material flow.

We also went to BGI to explain our project. BGI has rich experience in the genetic modification of thalli.

Feedback:

After hearing about our project, researchers there suggested that E. coli has a compact, less permeable membrane that limits electron transfer from the cell to the electrode, and that we could increase the permeability of E. coli cell membranes by adding porin-related genes.

We reviewed a large number of literature and found that oprF porin gene can increase the cell membrane permeability of Escherichia coli. Therefore, we synthesized the porin gene (oprF) by direct DNA synthesis method, regulated it with the constitutive promoter to ensure the continuous expression of the gene, and constructed our amplification system. The expression of the porin gene greatly improves the performance of our biosensor.

After the end of the Human Practice section, everyone put forward their own suggestions, some of which were related to the improvement of the specific steps of the experiment, and some of which were related to social publicity. Your positive attitude helps our team to know more about the needs and demands of the public, and the advice from the public is a valuable gift to our team. At the same time, we also introduced the project to experts in related fields. They provided us with many modification schemes, which played a significant role in promoting the design of our project.