Difference between revisions of "Team:Shiyan SY China/Project.html"

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In order to provide a solution, we design an engineered bacterium, secreting the OMP enzyme to degrade the common toxic pesticide residues. Its secretion is under the temperature control and can only be activated at specified temperature. To avoid the secondary pollution, a UV-induced suicide gene is inserted into the bacteria: upon exposure to UV or sunshine, the suicide procedure is induced. This purpose of the design is to remove toxic pesticide safely without affecting the environment.  
+
In order to provide a solution, we design an engineered bacterium, secreting the OpdA enzyme to degrade the common toxic pesticide residues. Its secretion is under the temperature control and can only be activated at specified temperature. To avoid the secondary pollution, a UV-induced suicide gene is inserted into the bacteria: upon exposure to UV or sunshine, the suicide procedure is induced. This purpose of the design is to remove toxic pesticide safely without affecting the environment.  
 
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<img src="https://static.igem.org/mediawiki/2015/f/fd/Project_nongyao.jpg" width="27%" class="genpicfloatright">  
 
<img src="https://static.igem.org/mediawiki/2015/f/fd/Project_nongyao.jpg" width="27%" class="genpicfloatright">  
 
<p>
 
<p>
The increasing environmental pollution and changeable climates make the insect pests on crops more serious. According to the statistical data from Chinese Academy of Agricultural Sciences, in recent years, there have been over seventy kinds of insect pests on vegetables and fruits. If these insect pests are not controlled, they will lead to total failures of crops, such as vegetables, fruits and grains. Faced with raging insect pests, the farmers have to constantly spray pesticides, and even use the high-toxic pesticides which are forbidden by our country. Therefore, as a result of the use of pesticides, a majority of vegetables and fruits contain pesticides above the permitted limits, but they still flow into thousands of families through channels such as vegetable markets, supermarkets and roadside stalls.
+
With the increased environmental pollution and climate change, pest problem becomes a serious issue in agriculture. According to the statistical data from Chinese Academy of Agricultural Sciences, in recent years, over seventy pest species have been recorded on vegetables and fruits. If not controlled, these pests could lead to complete wipeout of various crops, such as vegetables, fruits and grains. Therefore, to deal with the pest issue, the farmers have to constantly spray pesticides, and even use the high-toxic pesticides which are forbidden by China. As a result, a majority of vegetables and fruits, containing over dosed pesticides which are way above the permitted limits, get onto the dining tables of  thousands of families through channels such as farmer’s markets, supermarkets and roadside stalls.
 
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It is shown according to the statistics from World Health Organization, there are at least 500 000 pesticide poisoning accidents and 115 000 persons who die of pesticide poisoning annually all over the world. Moreover, over 85% of cancer cases and over 80 kinds of diseases are relevant to pesticide residues. In many big cities in China, the exceeding standard rate of pesticide residues on vegetables and fruits reached up to 47%.
+
According to the statistics from World Health Organization, there are at least 500,000 pesticide poison accidents per yearwith 115,000 death due to pesticide poisoning all over the world; furtherover 85% of cancer cases and 80 kinds of diseases are suspected to related to over-dosed pesticide usage. In many major cities in China, it is reported that over 47% vegetables and fruits on the market have over-dosed pesticide residues.
 
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</p>
 
</div>
 
</div>
 
<p>
 
<p>
At present, the pesticides which are used most widely are phosphorus pesticides and ester pesticides. The phosphorus and ester in these two pesticides can both cause damages to the mechanism of human bodies. 1. Organophosphorus pesticides, are organic composites which contain organophosphorus pesticides and are used to prevent plant diseases and insect pests. These pesticides have multiple varieties, high pesticide effects, wide applications and are easy to be broken down. Additionally, they generally will not accumulate in human bodies and animal bodies, and are highly important composites among pesticides. The organophosphorus pesticides produced currently are mostly insecticides, such as parathion, demeton, malathion, dimethoate, trichlorphon and dichlorvos which are often used. In recent years, organophosphorus pesticides such as bactericide and rodenticide have been synthesized. Organophosphorus pesticides have many varieties and can be divided into high-toxic, medium-toxic and low-toxic according to their degrees of toxicity. Toxicity of each variety can be different. A majority of organophosphorus pesticides belong to high-toxic and medium-toxic varieties while a minority of them are low-toxic. Only a gentle contact of small amount of high-toxic organophosphorus pesticides can cause poisoning while damages can be caused if a large amount of low-toxic organophosphorus pesticides enter human bodies. The amounts of organophosphorus inside different human bodies which can cause poisoning and death range from person to person. The poisoning symptoms which are caused by organophosphorus pesticides’ entering human bodies from digestive tracts are severer than those caused by common concentration of organophosphorus pesticides’ entering human bodies from respiratory tracts or skins while the disease attack rate by the former is also quicker than that by the latter. However, if a person inhales organophosphorus pesticides in large amounts or of high concentration, he or she can be attacked by disease within five minutes and dies quickly. The toxic effects organophosphorus pesticides have on human bodies are mainly to combine with cholinesterase to form phosphorylation cholinesterase. Then the activeness of cholinesterase is suppressed, which leads the enzymes to not being capable to break down acetylcholine. Consequently, the amount of acetylcholine which accumulates inside tissues is beyond limit and causes the cholinergic nerves to be overly stimulated, which leads to muscarinic, nicotinic and central nervous system symptoms.  
+
Currently, the mostly used pesticides are phosphorus pesticides and ester pesticides. The phosphorus and ester in these two pesticides can both cause human body damages to . 1. Organophosphorus pesticides, are organic composites to prevent plant diseases and insect pests. These pesticides have multiple varieties, high pesticide effects, wide applications and are easy to be broken down. Additionally, they generally will not accumulate in human bodies and animal bodies, and are one of the most widely used pesticides. The organophosphorus pesticide productscurrently are mostly insecticides. Most commone ones areparathion, demeton, malathion, dimethoate, trichlorphon and dichlorvos. In recent years, organophosphorus pesticides such as bactericide and rodenticide have also been synthesized. Organophosphorus pesticides have many varieties and can be divided into high-toxic, medium-toxic and low-toxic according to their degrees of toxicity. A majority of organophosphorus pesticides belong to high- and medium-toxic varieties while a minority of them are low-toxic. Only a gentle contact of small amount of high-toxic organophosphorus pesticides can cause poisoning, while in the contract, damages can only be caused if a large amount of low-toxic organophosphorus pesticides enter human bodies. The amounts of organophosphorus within human bodies which can cause poisoning or even death, varies upon individual conditions. The poisoning symptoms caused by oral intake of organophosphorus pesticides’ usually are severer than the ones caused by respiratory intake or skin contacts. Further, the onset speed is faster in oral intake comparing to other. However, if organophosphorus pesticides were respiratory intake in large amounts or with high concentration, it can cause death within five minutes. The molecular mechanism behind the toxic effects of organophosphorus pesticides is that  organophosphorus phosphorylates cholinesterase, an enzyme to degrade acetylcholine, ; this phosphorylation suppresses the degradation activity of cholinesterase . . Consequently, accumulated acetylcholine overly stimulates  the cholinergic nerves, which leads to muscarinic, nicotinic and other central nervous system symptoms.
 
</p>
 
</p>
 
<p>
 
<p>
Related studies prove that the sources of many diseases such as various cancers, leukemia, breast cancer, children of low intelligence and bad memory, meningitis, compounded diseases can be traced back to pesticide residues. People who always touch pesticides have a over 90% chance to suffer Parkinson’s disease. Additionally, contacts with pesticides can cause cardiovascualr and cerebrovascular diseases, diabetes and infertility. If eating fruits and vegetables with residual pesticides, people who are acutely poisoned will suffer symptoms such as headache, dizziness, vomit, stomachache and diarrhea. Apart from that chronic poisoning can lead to various diseases, pesticide residues can cause incurable deadly diseases (cancers) after accumulating in human bodies for about fifteen to twenty years.
+
Many studies indicated that over dosed pesticides could cause many diseases such as various cancers, Children's mental retardation, meningitis Parkinson’s disease, cardiovascualr and cerebrovascular diseases, diabetes and infertility. Acute symptoms associated with over dosed pesticides include headache, dizziness, vomit, stomachache and diarrhea.  
 
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Faced with the stress effects human pollution such as pesticides has on environment, nature has evolved many methods to deal with these problems. For example, many natural micro-organisms have the characteristic of degrading organophosphorus pesticides. Currently the micro-organisms which have been found being capable to degrade organophosphorus pesticides include bacteria, fungus, actinomycete and alga. As the research goes further, people find that these degrading bacteria degrade pesticides by secreting a kind of enzyme which can hydrolyze phosphaester bonds-organophosphorus-degradation enzyme. Because each organophosphorus pesticide has similar structure and is only different in substituent groups, one kind of organophosphorus-degradation enzyme can always degrade multiple kinds of organophosphorus pesticides. Organophosphorus-degradation enzyme has been widely acknowledged to be the most potential new method to eliminate pesticide residues currently. At present, many enzymes have been identified to be used to degrade organophosphate pesticides. Among these enzymes, organophosphorus-degradation enzyme (opdA) which comes from Agrobacterium radiobacter P230 of radioactive agrobactium tumefaciens genus has wider substrate and higher enzyme-catalyst efficiency. In recent years, the research on the structure and function of organophosphorus-degradation enzyme has gained relatively big development and comes into the molecule level, which makes it possible to improve the properties of organophosphorus-degradation enzyme through genetic engineering and protein engineering and invent organophosphorus-degradation enzyme products which meet requirements of different application fields.
+
Faced with the stress of human pollution such as pesticides, nature itself has evolved many methods to deal with these problems. For example, many natural micro-organisms contain enzymes to degrade organophosphorus pesticides. Currently the micro-organisms which are capable to degrade organophosphorus pesticides include bacteria, fungus, actinomycete and alga. As the research goes further, people find that these degrading effects come from secreting an enzyme, which can hydrolyze phosphoester bonds, organophosphorus degradation enzyme. Because each organophosphorus pesticide has similar structure and protein sequence, one kind of organophosphorus degradation enzyme is capable todegrade multiple kinds of organophosphorus pesticides. Organophosphorus-degradation enzyme has been mostly recognized as the best method to eliminate pesticide residues currently. At present, many enzymes have been identified to be used to degrade organophosphate pesticides. Among these enzymes, the organophosphorus-degradation enzyme (opdA) which comes from Agrobacterium radiobacter P230 has wider targets and higher enzyme-catalyst efficiency. In recent years, the research on the structure and function of organophosphorus-degradation enzyme has gained promising progress,.  Thus, it is possible to improve the properties of organophosphorus-degradation enzyme through genetic engineering and protein engineering method, which meet requirements of different applications.
 
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2)We will use organophosphorus-degradation enzyme opdA to achieve the elimination of residual organophosphorus pesticides on fruits and vegetables.
+
2)In this project, we will use organophosphorus-degradation enzyme opdA to eliminate residual organophosphorus pesticides on fruits and vegetables.
 
</h>
 
</h>
 
<p>
 
<p>
The organophosphorus-degradation enzyme (opdA) gene opda (NCBI genbank:Accession: AY043245.2) programmed by Agrobacterium radiobacter bacteria contains 1 155 basic groups in total and programs 384 amino acid residues. The front end of protein sequence is signal peptide sequence while the back end is degradation-enzyme sequence. The nucleic acid sequence and amino acid sequence are as follows:
+
The organophosphorus-degradation enzyme (opdA) gene opdA (NCBI genbank:Accession: AY043245.2) programmed by Agrobacterium radiobacter contains 1,155 nucleic acids, programming 384 amino acid residues. The N-terminal of protein sequence is the signal peptide while the C-terminal is the degradation-enzyme sequence. The nucleic acid sequence and amino acid sequence are as follows:
 
</p>
 
</p>
 
<h style="font-size:14px;font-weight: bold;">
 
<h style="font-size:14px;font-weight: bold;">
Nucleic sequence (DNA sequence)
+
Nucleotide sequence
 
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Amino acid sequence (protein sequence)
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Amino acid sequence  
 
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3) Colibacillus genetically engineered bacteria
+
3)Genetically engineered E.Colibacteria
 
</h>
 
</h>
 
<p>
 
<p>
In this project, we will use colibacillus to construct genetically engineered bacteria which can secrete organophosphorus-degradation enzyme opdA protein, to achieve the biodegradation of organophosphorus residues and eliminate the pollution by pesticides.
+
In this project, we will use E. Coli to construct genetically engineered bacteria which can secrete organophosphorus-degradation enzyme opdA protein, to eliminate the pesticides.
 
</p>
 
</p>
 
<p>
 
<p>
Genetically engineered bacteria are bacteria which can channel target gene into bacteria to express the genes and produce required protein. These bacteria which are equipped with new inheritable characters given by humans are called genetically engineered bacteria.
+
Genetically engineered bacteria are bacteria which can channel target gene into bacteria to express the genes and produce required protein.  
 
</p>
 
</p>
 
<p>
 
<p>
Currently, the genetically engineered bacteria which are used most widely all over the world are still colibacillus because colibacillus have explicit genetic background, grow fast, have no resistance toward most antibiotics, are easy to be controlled in growth and activeness, are easy to be used in any production magnitude from laboratory production to industry production. (For example: scientists introduce human insulin gene into colibacillus cells and combine insulin gene with genetic materials of colibacillus. Human insulin gene directs colibacillus to product human insulin in colibacillus cells. As they reproduce, the insulin gene also gets transmitted down generation after generation and colibacillus of later generations can also produce insulin. The genetically engineered bacteria equipped with human insulin gene are put into large fermentor, which can provide them with appropriate conditions and nutrients, to be cultured manually. They can reproduce in large populations and produce large amount of human insulin. The colibacillus have become the “live factory” to produce insulin. In 1981, human insulin gene products were put into market and solved the problem of lack of insulin sources).
+
Currently, the mostly used genetically engineered bacteria all over the world are still E. Coli.  E. Coli have explicit genetic background, fast growth rate, limited antibiotics resistance, Thus, E. Coli, are easy to be used in any production magnitude from laboratory to industry production. (For example: scientists introduced human insulin gene into E. Coli genome. E. Coli can express functional human insulin protein, which is used as a medicine for diabetes treatment. Human insulin production from E. coli has been applied to industry and this method is also widely used in biotech industry for other drug purposes In 1981, human insulin gene products were put into market and solved the problem of lack of insulin sources).
 
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<div>&nbsp;</div>
 
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In this project, the Thermometer RNA we use has a sensitive temperature of 32℃, which means in environment above 32℃, RNA translation process can be started. Its DNA sequence is as follows:
+
In this project, the Thermometer RNA we use has a sensitive temperature of 32℃, which means in environment above 32C, RNA translation process can be started. Its DNA sequence is as follows:
 
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</h>
 
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<p>
In this project, opdA enzyme which is expressed by genetic engineering still cannot be directly used in degradation of organophosphorus pesticides because colibacillus genetically engineered bacteria can only express genetically engineered protein designed by humans in cell membranes, which will cause expressed opdA enzyme protein to accumulate in large amounts inside the genetically engineered bacteria and thus the protein cannot contact with external organophosphorus pesticides to accomplish the degradation process and poisons genetically engineered bacteria. Therefore, we need to come up with methods to transfer the expressed opdA protein outside the genetically engineered bacteria. We need the structure of signal peptide to help in this process.
+
In this project, to secrete the opdA enzyme from inside the bacteria to outside, an ompA signal peptide is introduced into the construction. By adding this secreting peptide, OpdA is secreted outside the E. Coli, without its accumulating inside.  
 
</p>
 
</p>
 
<p>
 
<p>
Signal peptide often refers to N-end amino acid sequence which is used to direct the trans-membrane process (orientation) in newly compounded peptide chains. There is a segment of RNA area programming hydrophobi amino acid sequence which generally lies after initiation codon. This amino acid sequence is called signal peptide sequence, which takes charge of introducing protein into sub-cellular organelles which contain different membrane structures. If the function of this signal peptide is to introduce and secrete compounded protein outside the cell walls, this signal peptide is called secretion signal peptide.
+
Signal peptide often refers to a N-terminal amino acid sequence which is used to direct the trans-membrane process in newly synthesized proteins. There is a segment of RNA area programming hydrophobic amino acid sequence which is generally behind the start codon. This amino acid sequence is called signal peptide sequence, which introduces  protein into sub-cellular organelles which contain different membrane structures. If the function of this signal peptide is to secrete protein outside the cell walls, this signal peptide is called secretion signal peptide.
 
</p>
 
</p>
 
<p>
 
<p>
As we know, on natural conditions, ompA which exists inside Agrobacterium radiobacter bacteria has its own signal peptide. However, this original signal peptide is only used by Agrobacterium radiobacter and is not necessarily useful in colibacillus genetically engineered bacteria. Therefore, we need to select some signal peptides which can be used by colibacillus, to achieve our plan.
+
As we know, on natural conditions, ompA which exists inside Agrobacterium radiobacter bacteria has its own signal peptide. However, this original signal peptide is only used by Agrobacterium radiobacter and is not necessarily functional inE. Coli. Therefore, we need to select an E. colisignal peptides to achieve our plan.
 
</p>
 
</p>
 
<p>
 
<p>
The ompA signal peptide used in this project is one of the secretion signal peptides which are used most widely in colibacillus genetically engineered bacteria and can lead to expressing its downstream protein molecules to transfer across cell walls of host colibacillus and secrete target protein outside the host bacteria. The DNA sequence of this signal peptide is as follows:
+
The ompA signal peptide used in this project is one of the E. coli secreting signal peptides and can lead secretion of its downstream protein outside of its host E. coli. The DNA sequence of this signal peptide is as follows:
 
</p>
 
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</h>
 
</h>
 
<p>
 
<p>
In this project, we cannot only consider how to use genetically engineered bacteria to eliminate organophosphorus. Thus, after organophosphorus is eliminated, how should we deal with the rest genetically engineered bacteria? This is what we must pay attention to. Genetically engineered bacteria, after all, come from colibacillus. We don’t want to see it directly released into environment or continued to remain on the surface of fruits and vegetables, thus we must design a method or equipment to eliminate them. Consequently, we decide to design a suicide gene in our genetically engineered bacteria, which is not expressed commonly and only expresses suicide protein in special environments to eliminate the bacteria and avoid “secondary pollution” problems caused by genetically engineered bacteria.
+
In this project, we consider not only how to use genetically engineered bacteria to eliminate organophosphorus, but also after organophosphorus is eliminated, how we should deal with the rest genetically engineered bacteria. Genetically engineered bacteria, after all, come from E. coli. We don’t want them released into environment or remaining on the surface of fruits and vegetables. Thus we must design a method to eliminate them. Consequently, we decide to design a suicide gene into our genetically engineered bacteria, which is inactivated under normal condition and only activated under special environments to eliminate the bacteria and avoid “secondary pollution”.
 
</p>
 
</p>
 
<p>
 
<p>
In this project, we select suicide gene ccdb, ccdB is a currently known toxin system, which exists in pathogenic colibacillus F plasmid. The ccdB gene programs a kind of toxin protein CcdB. On conditions where there is a lack of antitoxin, CcdB poisons gyrase inside cells to interfere with the synthesis of DNA and damage host cells. The ccdb sequence we use in this project is as follows:
+
To achieve the above goal, we select suicide gene ccdb. ccdB is a known toxin system, which exists in pathogenic E. coli F plasmid. The ccdB gene programs a toxin protein CcdB. On conditions where there is a lack of antitoxin, CcdB poisons gyrase inside cells to interfere with the DNAsynthesis and damage host cells. The ccdb sequence we use in this project is as follows:
 
</p>
 
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</h>
 
</h>
 
<p>
 
<p>
In the project we chose a kind of RecA(SOS) promoter to control to suicide gene ccdB to express. It works because when the bacteria receive ultraviolet rays, DNA get injured so that the bacteria will guide RecA repairing protein’s expression. The protein can start RecA(SOS) promoter to drive the lower ccdB suicide gene’s transcription. In this way, we can control our engineering bacteria by eliminating them with ultraviolet rays to avoid secondary pollution.
+
In the project we chose a RecA(SOS) promoter to control to suicide gene ccdB to express. When the bacteria receive ultraviolet lights, DNA injury activate the RecA repairing system. The system can activate RecA(SOS) promoter to drive the downstream ccdB suicide gene’s transcription. In this way, we can control our engineering bacteria by eliminating them with ultraviolet rays to avoid secondary pollution.
 
</p>
 
</p>
 
<p>
 
<p>
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8)The biology module we construct in this project referred to a lot of information from other teams of igem in past years and from other scientific projects in the society. The information was coordinated and integrated in this project, and formed the research design and contents of this project.
+
8)The design of the biobricks in this project referred to a lot of information from other igem teams in past years and from other scientific projects in the society. The information was coordinated and integrated in this project, and formed the research design and contents of this project.
 
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<p>
 
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</p>
 
</p>
 
<p>
 
<p>
(4)The repair enzyme inducement initiation codon RecA (SOS) sequence used in this project referred to BB_J22106 from igem
+
(4)The repair enzyme induced promoter  RecA (SOS) sequence used in this project referred to BB_J22106 from igem
 
</p>
 
</p>
 
<p>
 
<p>

Revision as of 01:25, 17 September 2015

IGEM-PROJECT

With increased agriculture activities around the world, it becomes a common practice to use pesticides to manage pest problem. Runoff can carry field pesticide into aquatic environment while wind can carry them to other fields, potentially affecting other species. Over time, repeated application increases pest resistance and facilitate the pest resurgence. Further, especially in China, toxic pesticide residues on green vegetable and fruits become a major public health problem.

In order to provide a solution, we design an engineered bacterium, secreting the OpdA enzyme to degrade the common toxic pesticide residues. Its secretion is under the temperature control and can only be activated at specified temperature. To avoid the secondary pollution, a UV-induced suicide gene is inserted into the bacteria: upon exposure to UV or sunshine, the suicide procedure is induced. This purpose of the design is to remove toxic pesticide safely without affecting the environment.

With the increased environmental pollution and climate change, pest problem becomes a serious issue in agriculture. According to the statistical data from Chinese Academy of Agricultural Sciences, in recent years, over seventy pest species have been recorded on vegetables and fruits. If not controlled, these pests could lead to complete wipeout of various crops, such as vegetables, fruits and grains. Therefore, to deal with the pest issue, the farmers have to constantly spray pesticides, and even use the high-toxic pesticides which are forbidden by China. As a result, a majority of vegetables and fruits, containing over dosed pesticides which are way above the permitted limits, get onto the dining tables of thousands of families through channels such as farmer’s markets, supermarkets and roadside stalls.

According to the statistics from World Health Organization, there are at least 500,000 pesticide poison accidents per yearwith 115,000 death due to pesticide poisoning all over the world; furtherover 85% of cancer cases and 80 kinds of diseases are suspected to related to over-dosed pesticide usage. In many major cities in China, it is reported that over 47% vegetables and fruits on the market have over-dosed pesticide residues.

Currently, the mostly used pesticides are phosphorus pesticides and ester pesticides. The phosphorus and ester in these two pesticides can both cause human body damages to . 1. Organophosphorus pesticides, are organic composites to prevent plant diseases and insect pests. These pesticides have multiple varieties, high pesticide effects, wide applications and are easy to be broken down. Additionally, they generally will not accumulate in human bodies and animal bodies, and are one of the most widely used pesticides. The organophosphorus pesticide productscurrently are mostly insecticides. Most commone ones areparathion, demeton, malathion, dimethoate, trichlorphon and dichlorvos. In recent years, organophosphorus pesticides such as bactericide and rodenticide have also been synthesized. Organophosphorus pesticides have many varieties and can be divided into high-toxic, medium-toxic and low-toxic according to their degrees of toxicity. A majority of organophosphorus pesticides belong to high- and medium-toxic varieties while a minority of them are low-toxic. Only a gentle contact of small amount of high-toxic organophosphorus pesticides can cause poisoning, while in the contract, damages can only be caused if a large amount of low-toxic organophosphorus pesticides enter human bodies. The amounts of organophosphorus within human bodies which can cause poisoning or even death, varies upon individual conditions. The poisoning symptoms caused by oral intake of organophosphorus pesticides’ usually are severer than the ones caused by respiratory intake or skin contacts. Further, the onset speed is faster in oral intake comparing to other. However, if organophosphorus pesticides were respiratory intake in large amounts or with high concentration, it can cause death within five minutes. The molecular mechanism behind the toxic effects of organophosphorus pesticides is that organophosphorus phosphorylates cholinesterase, an enzyme to degrade acetylcholine, ; this phosphorylation suppresses the degradation activity of cholinesterase . . Consequently, accumulated acetylcholine overly stimulates the cholinergic nerves, which leads to muscarinic, nicotinic and other central nervous system symptoms.

Many studies indicated that over dosed pesticides could cause many diseases such as various cancers, Children's mental retardation, meningitis Parkinson’s disease, cardiovascualr and cerebrovascular diseases, diabetes and infertility. Acute symptoms associated with over dosed pesticides include headache, dizziness, vomit, stomachache and diarrhea.

Experimental Design:
 
1.Inserted PARTS design:
 

Note: F1:…,F2:…, F3:…, F4: ….

 
2.Final Plasmid Design:
 
 
Experimental Procedure:
 
 
1)Micro-organisms degrades organophosphorus, and organophosphorus-degradation enzyme opdA

Faced with the stress of human pollution such as pesticides, nature itself has evolved many methods to deal with these problems. For example, many natural micro-organisms contain enzymes to degrade organophosphorus pesticides. Currently the micro-organisms which are capable to degrade organophosphorus pesticides include bacteria, fungus, actinomycete and alga. As the research goes further, people find that these degrading effects come from secreting an enzyme, which can hydrolyze phosphoester bonds, organophosphorus degradation enzyme. Because each organophosphorus pesticide has similar structure and protein sequence, one kind of organophosphorus degradation enzyme is capable todegrade multiple kinds of organophosphorus pesticides. Organophosphorus-degradation enzyme has been mostly recognized as the best method to eliminate pesticide residues currently. At present, many enzymes have been identified to be used to degrade organophosphate pesticides. Among these enzymes, the organophosphorus-degradation enzyme (opdA) which comes from Agrobacterium radiobacter P230 has wider targets and higher enzyme-catalyst efficiency. In recent years, the research on the structure and function of organophosphorus-degradation enzyme has gained promising progress,. Thus, it is possible to improve the properties of organophosphorus-degradation enzyme through genetic engineering and protein engineering method, which meet requirements of different applications.

2)In this project, we will use organophosphorus-degradation enzyme opdA to eliminate residual organophosphorus pesticides on fruits and vegetables.

The organophosphorus-degradation enzyme (opdA) gene opdA (NCBI genbank:Accession: AY043245.2) programmed by Agrobacterium radiobacter contains 1,155 nucleic acids, programming 384 amino acid residues. The N-terminal of protein sequence is the signal peptide while the C-terminal is the degradation-enzyme sequence. The nucleic acid sequence and amino acid sequence are as follows:

Nucleotide sequence

at gcaaacgaga agagatgcac ttaagtctgc ggccgcaata actctgctcg gcggcttggc tgggtgtgca agcatggccc gaccaatcgg tacaggcgat ctgattaata ctgttcgcgg ccccattcca gtttcggaag cgggcttcac actgacccat gagcatatct gcggcagttc ggcgggattc ctacgtgcgt ggccggagtt tttcggtagc cgcaaagctc tagcggaaaa ggctgtgaga ggattacgcc atgccagatc ggctggcgtg caaaccatcg tcgatgtgtc gactttcgat atcggtcgtg acgtccgttt attggccgaa gtttcgcggg ccgccgacgt gcatatcgtg gcggcgactg gcttatggtt cgacccgcca ctttcaatgc gaatgcgcag cgtcgaagaa ctgacccagt tcttcctgcg tgaaatccaa catggcatcg aagacaccgg tattagggcg ggcattatca aggtcgcgac cacagggaag gcgaccccct ttcaagagtt ggtgttaaag gcagccgcgc gggccagctt ggccaccggt gttccggtaa ccactcacac gtcagcaagt cagcgcgatg gcgagcagca ggcagccata tttgaatccg aaggtttgag cccctcacgg gtttgtatcg gtcacagcga tgatactgac gatttgagct acctaaccgg cctcgctgcg cgcggatacc tcgtcggttt agatcgcatg ccgtacagtg cgattggtct agaaggcaat gcgagtgcat tagcgctctt tggtactcgg tcgtggcaaa caagggctct cttgatcaag gcgctcatcg accgaggcta caaggatcga atcctcgtct cccatgactg gctgttcggg ttttcgagct atgtcacgaa catcatggac gtaatggatc gcataaaccc agatggaatg gccttcgtcc ctctgagagt gatcccattc ctacgagaga agggcgtccc gccggaaacg ctagcaggcg taaccgtggc caatcccgcg cggttcttgt caccgaccgt gcgggccgtc gtgacacgat ctgaaacttc ccgccctgcc gcgcctattc cccgtcaaga taccgaacga tga

Amino acid sequence

MQTRRDALKSAAAITLLGGLAGCASMARPIGTGDLINTVRGPIPVSEAGFTLTHEHICGSSAGFLRAWPEFFGSRKALAEKAVRGLRHARSAGVQTIVDVSTFDIGRDVRLLAEVSRAADVHIVAATGLWFDPPLSMRMRSVEELTQFFLREIQHGIEDTGIRAGIIKVATTGKATPFQELVLKAAARASLATGVPVTTHTSASQRDGEQQAAIFESEGLSPSRVCIGHSDDTDDLSYLTGLAARGYLVGLDRMPYSAIGLEGNASALALFGTRSWQTRALLIKALIDRGYKDRILVSHDWLFGFSSYVTNIMDVMDRINPDGMAFVPLRVIPFLREKGVPPETLAGVTVANPARFLSPTVRAVVTRSETSRPAAPIPRQDTER

DNA SEQUENCE

at gcaaacgaga agagatgcac ttaagtctgc ggccgcaata actctgctcg gcggcttggc tgggtgtgca agcatggccc gaccaatcgg tacaggcgat ctgattaata ctgttcgcgg ccccattcca gtttcggaag cgggcttcac actgacccat gagcatatct gcggcagttc ggcgggattc ctacgtgcgt ggccggagtt tttcggtagc cgcaaagctc tagcggaaaa ggctgtgaga ggattacgcc atgccagatc ggctggcgtg caaaccatcg tcgatgtgtc gactttcgat atcggtcgtg acgtccgttt attggccgaa gtttcgcggg ccgccgacgt gcatatcgtg gcggcgactg gcttatggtt cgacccgcca ctttcaatgc gaatgcgcag cgtcgaagaa ctgacccagt tcttcctgcg tgaaatccaa catggcatcg aagacaccgg tattagggcg ggcattatca aggtcgcgac cacagggaag gcgaccccct ttcaagagtt ggtgttaaag gcagccgcgc gggccagctt ggccaccggt gttccggtaa ccactcacac gtcagcaagt cagcgcgatg gcgagcagca ggcagccata tttgaatccg aaggtttgag cccctcacgg gtttgtatcg gtcacagcga tgatactgac gatttgagct acctaaccgg cctcgctgcg cgcggatacc tcgtcggttt agatcgcatg ccgtacagtg cgattggtct agaaggcaat gcgagtgcat tagcgctctt tggtactcgg tcgtggcaaa caagggctct cttgatcaag hgcgctcatcg accgaggcta caaggatcga atcctcgtct cccatgactg gctgttcggg ttttcgagct atgtcacgaa catcatggac gtaatggatc gcataaaccc agatggaatg gccttcgtcc ctctgagagt gatcccattc ctacgagaga agggcgtccc gccggaaacg ctagcaggcg taaccgtggc caatcccgcg cggttcttgt caccgaccgt gcgggccgtc gtgacacgat ctgaaacttc ccgccctgcc gcgcctattc cccgtcaaga taccgaacga tga

PROTEIN SEQUENCE

MQTRRDALKSAAAITLLGGLAGCASMARPIGTGDLINTVRGPIPVSEAGFTLTHEHICGSSAGFLRAWPEFFGSRKALAEKAVRGLRHARSAGVQTIVDVSTFDIGRDVRLLAEVSRAADVHIVAATGLWFDPPLSMRMRSVEELTQFFLREIQHGIEDTGIRAGIIKVATTGKATPFQELVLKAAARASLATGVPVTTHTSASQRDGEQQAAIFESEGLSPSRVCIGHSDDTDDLSYLTGLAARGYLVGLDRMPYSAIGLEGNASALALFGTRSWQTRALLIKALIDRGYKDRILVSHDWLFGFSSYVTNIMDVMDRINPDGMAFVPLRVIPFLREKGVPPETLAGVTVANPARFLSPTVRAVVTRSETSRPAAPIPRQDTER

3)Genetically engineered E.Colibacteria

In this project, we will use E. Coli to construct genetically engineered bacteria which can secrete organophosphorus-degradation enzyme opdA protein, to eliminate the pesticides.

Genetically engineered bacteria are bacteria which can channel target gene into bacteria to express the genes and produce required protein.

Currently, the mostly used genetically engineered bacteria all over the world are still E. Coli. E. Coli have explicit genetic background, fast growth rate, limited antibiotics resistance, Thus, E. Coli, are easy to be used in any production magnitude from laboratory to industry production. (For example: scientists introduced human insulin gene into E. Coli genome. E. Coli can express functional human insulin protein, which is used as a medicine for diabetes treatment. Human insulin production from E. coli has been applied to industry and this method is also widely used in biotech industry for other drug purposes In 1981, human insulin gene products were put into market and solved the problem of lack of insulin sources).

4)RNA Thermometer

An RNA thermometer (or RNA thermosensor) is a temperature-sensitive non-coding RNA molecule which regulates gene expression. RNA thermometers often regulate genes required during either a heat shock or cold shock response. In general, RNA thermometers operate by changing their secondary structure in response to temperature fluctuations. This structural transition can then expose or occlude important regions of RNA such as a ribosome binding site, which then affects the translation rate of a nearby protein-coding gene.

 

Below is a schematic diagram of Thermometer RNA:

 
 

In this project, the Thermometer RNA we use has a sensitive temperature of 32℃, which means in environment above 32C, RNA translation process can be started. Its DNA sequence is as follows:

Ccgggcgcccttcgggggcccggcggagacgggcgccggaggtgtccgacgcctgctcgtccagtctttgctcagtggaggattactag

5)ompA signal peptide

In this project, to secrete the opdA enzyme from inside the bacteria to outside, an ompA signal peptide is introduced into the construction. By adding this secreting peptide, OpdA is secreted outside the E. Coli, without its accumulating inside.

Signal peptide often refers to a N-terminal amino acid sequence which is used to direct the trans-membrane process in newly synthesized proteins. There is a segment of RNA area programming hydrophobic amino acid sequence which is generally behind the start codon. This amino acid sequence is called signal peptide sequence, which introduces protein into sub-cellular organelles which contain different membrane structures. If the function of this signal peptide is to secrete protein outside the cell walls, this signal peptide is called secretion signal peptide.

As we know, on natural conditions, ompA which exists inside Agrobacterium radiobacter bacteria has its own signal peptide. However, this original signal peptide is only used by Agrobacterium radiobacter and is not necessarily functional inE. Coli. Therefore, we need to select an E. colisignal peptides to achieve our plan.

The ompA signal peptide used in this project is one of the E. coli secreting signal peptides and can lead secretion of its downstream protein outside of its host E. coli. The DNA sequence of this signal peptide is as follows:

Atgaaaaaaaccgctatcgcgatcgcagttgcactggctggtttcgctaccgttgcgcaggcc

6)Suicide gene ccdb

In this project, we consider not only how to use genetically engineered bacteria to eliminate organophosphorus, but also after organophosphorus is eliminated, how we should deal with the rest genetically engineered bacteria. Genetically engineered bacteria, after all, come from E. coli. We don’t want them released into environment or remaining on the surface of fruits and vegetables. Thus we must design a method to eliminate them. Consequently, we decide to design a suicide gene into our genetically engineered bacteria, which is inactivated under normal condition and only activated under special environments to eliminate the bacteria and avoid “secondary pollution”.

To achieve the above goal, we select suicide gene ccdb. ccdB is a known toxin system, which exists in pathogenic E. coli F plasmid. The ccdB gene programs a toxin protein CcdB. On conditions where there is a lack of antitoxin, CcdB poisons gyrase inside cells to interfere with the DNAsynthesis and damage host cells. The ccdb sequence we use in this project is as follows:

Atgcagtttaaggtttacacctataaaagagagagccgttatcgtctgtttgtggatgtacagagtgatattattgacacgcccgggcgacggatggtgatccccctggccagtgcacgtctgctgtcagataaagtctcccgtgaactttacccggtggtgcatatcggggatgaaagctggcgcatgatgaccaccgatatggccagtgtgccggtctccgttatcggggaagaagtggctgatctcagccaccgcgaaaatgacatcaaaaacgccattaacctgatgttctggggaatataa

7)RecA(SOS) promoter

In the project we chose a RecA(SOS) promoter to control to suicide gene ccdB to express. When the bacteria receive ultraviolet lights, DNA injury activate the RecA repairing system. The system can activate RecA(SOS) promoter to drive the downstream ccdB suicide gene’s transcription. In this way, we can control our engineering bacteria by eliminating them with ultraviolet rays to avoid secondary pollution.

The ccdb sequence we use in this project is as follows:

Aacaatttctacaaaacacttgatactgtatgagcatacagtataattgcttcaacagaacatattgactatccggtattacccggcatgacaggagtaaaaatggctatcgacgaaaacaaacagaaagcgttggcggcagcactgggccagattgagaaacaatttggtaaaggctccatcatgtaataa

8)The design of the biobricks in this project referred to a lot of information from other igem teams in past years and from other scientific projects in the society. The information was coordinated and integrated in this project, and formed the research design and contents of this project.

(1)The strong initiation sequence used in this project referred to BB_J23106 from igem

(2)The RNA thermometer sequence used in this project referred to BB_K115017 from igem

(3)The organophosphorus-degradation enzyme opdA gene sequence used in this project referred to BB_K21509, BB_K215091 and BB_K1010008 from igem

(4)The repair enzyme induced promoter RecA (SOS) sequence used in this project referred to BB_J22106 from igem

(5)The suicide gene ccdB sequence used in this project referred to BB_K145151 and BB_K1010007 from igem

(6)The ompA signal peptide sequence used in this project referred to sequence with the code AJ617284.1 from GenBank

Protocols on basic experiment steps
 
Plasmid extraction (using AXYgene kit)

1.Get 1-3ml bacteria solution, centrifuge the solution for 30 seconds with the speed of 10000rpm and collect bacteria cells

2.Pour away supernate culture medium and make bacteria cells float in 250μl solution S1, blow and beat evenly

3.Add 250μl solution S2, mix the total solution upside down gently, put them for no more than 5 minutes under room temperature

4.Add 350μl solution S3, mix the total solution upside down gently and slowly, centrifuge the solution for 12 minutes with the speed of 12000rpm

5.Draw supernate carefully and add the supernate into nucleic acid combination cylinder, put it quietly under room temperature for 1 minute

6.Centrifuge the above for 30 seconds with the speed of 12000rpm, and pour away effluent fluid

7.Add 500μl cleaning mixture W1 into nucleic acid combination cylinder, and centrifuge it for 30 seconds with the speed of 12000rpm, pour away the effluent fluid

8.Add 750μl cleaning mixture W2 into nucleic acid combination cylinder, and centrifuge it for 30 seconds with the speed of 12000rpm,pour away the effluent fluid

9.Repeat above steps again

10.Centrifuge for 1 minute with the speed of 12000rpm, and thoroughly get rid of residual W2

11.Put nucleic acid combination cylinder into new 1.5ml centrifuge tube, add 50-100μl, and put under room temperature for 1 minute

12.Centrifuge for 1 minute with the speed of 12000rpm, and collect plasmid solution

PCR amplification operations:

1. PCR reaction system: (25μl)

10 X buffer 2.5μl

Upstream primer 1μl

Downstream primer 1μl

dNTP 2μl

Module plasmid DNA 1μl

Taq enzyme 0.2μl

Sterile super-nature water added the volume to 25μl

2. PCR reaction conditions:

Denaturation for 5 minutes under 95℃;

Denaturation for 30 seconds under 95℃;

Annealing for 30 seconds under 55℃;

Extension under 72℃, extension time is determined by different length of sequence;

Return to (2), and carry out 29 circulations of above steps;

Extension for 10 minutes under 72℃, storage under 4℃

PCR produce digestive gel recycle

1.Under ultraviolet light, carefully cut off agar block which contains target DNA, put it into 1.5ml centrifuge tube;

2.Add two-times volume of sol solution A (add 200μl sol solution A into each 100mg agar block), heat it in water under 80℃ until the block is completely dissolved, mix evenly and cool to room temperature;

3.Put dissolved solution into gel recycle centrifuge tube, and centrifuge for 30 seconds with the speed of 10000rpm, then the DNA is attached to cylinder;

4.Add 450μl cleaning solution B into centrifuge tube, and centrifuge for 1 minute with the speed of 12000rpm, pour away the solution inside the tube;

5.Wash again using solution B;

6.Put absorption cylinder into a clean EP tube, add 30μl eluent C into the center of absorption membrane in centrifuge tube;

7.Put it quietly under 37℃ for 5 minutes, and centrifuge for 2 minutes with the speed of 12000rpm, and thus purified DNA is eluted into the solution.

Double enzyme digestion of plasmid and PCR product

Use corresponding nucleic acid endonuclease to carry out double enzyme digestion on PCR gene product or plasmid DNA segment which is purified by above digestive gel recycle kit, the digestive products are recycled and stored for future use after purified by purification kit. Enzyme digestion conditions are as follows:

10xH Buffer 5μl

Endonuclease 1 2μl

Endonuclease 2 2μl

Plasmid DNA less than 1μg

Sterile super-pure water added to the volume of 50μl

Double enzyme digestion reaction condition: 37℃, 3-4 hours

Connection and construction of enzyme digestion produces and relevant carrier

Connect the segment gene product obtained from above double enzyme digestion and plasmid DNA segment on the corresponding expression carrier which is also processed by the same enzyme respectively, the connection system is as follows:

10 x T4 connection buffer 2μl

Linear plasmid DNA 3μl

Endonuclease 2 2μl

Connection segment DNA the amount of molecules are 3-10 times more than plasmid DNA

T4 DNA ligase 1μl

Sterile super-pure water added to the volume of 20μl

Connection conditions: under 16℃ for 4 hours

Competence manufacture

(1)Get single colony of colibacillus (or the ratio of bacteria solution and culture medium is 1:1000), inoculate it to 1000ml LB culture medium, culture under 37℃ for 4 hours with the speed of 200rpm.

(2)Get 50ml centrifuge tube, pour cultured bacteria solution into the tube and put the tube into ice to cool for 10 minutes, and centrifuge for 10 minutes with the speed of 4000rpm.

(3)Pour away the bacteria solution thoroughly, re-suspend the bacteria cells using 0.1M calcium chloride solution which is pre-cooled to 0℃, shake to make the bacteria float, do not use oscillator, combine each tube of bacteria solution into one centrifuge tube.

(4)Centrifuge for 10 minutes with a speed of 4000rpm.

(5)Pour away the bacteria solution thoroughly, re-suspend the bacteria cells using 10ml of 0.1M calcium chloride solution which is pre-cooled to 0℃,add glycerin with a final concentration of 10%, and divide them into 100 microlitres per tube and store them under -80℃.

Connection product transformation

(1)Get 0.1ml competent cells, and put them on ice to naturally and thoroughly melt;

(2)Add about 10μl recombinant expression carrier connection products, and bath them in ice for 30 minutes;

(3)Put them in water bath under 42℃, and heat shock for exactly 90 seconds, and immediately bath them in ice for 2 minutes;

(4)Add 0.8ml LB culture medium, and slowly shake under 37℃ for 60 minutes;

(5)Draw appropriate amount of bacteria solution and coat LB plate which contains appropriate amount of insulin (45μg/ml chlorampenicol), and put the plate under room temperature until the solution is absorbed;

(5)Draw appropriate amount of bacteria solution and coat LB plate which contains appropriate amount of insulin (45μg/ml chlorampenicol), and put the plate under room temperature until the solution is absorbed;

(6)Place the plate upside down, overnight culture under 37℃.The next day, select positive single cloning colonies.

Project Achievement

The project designed a biology module which integrates multiple bio-functional components. This module can make the genetically engineered bacteria induced by temperature to produce organophosphorus-degradation enzyme opdA in order to eliminate the organophosphorus pesticides pollution in the environment and activate suicide gene under ultraviolet light, which avoids the secondary pollution problems posed by genetically engineered bacteria.

The project used methods of both synthetic biology and genetic engineering and successfully assembled this biology module outside externally, and transferred it to colibacillus to construct genetically engineered bacteria which can reproduce.

Future Plans for Project

Explore and optimize the growth and function culture conditions for genetically engineered bacteria which contain this biology module, and determine the best bacteria and growth conditions to be used to collect the scale of bacteria used in this method.

Evaluate the processing effects the genetically engineered bacteria which contain this biology module have on organophosphorus pesticides pollution in natural environments, such as the surfaces of vegetables and fruits which are polluted by organophosphorus pesticides or the soils and waters which are polluted by organophosphorus pesticides, and the field elimination effects on organophosphorus pesticides.

On the basis of this biology module, the project further developed the module functions, for example, functional degradation enzyme systems of other pesticides or other organic pollutants can be introduced into this biology module on trial to achieve the degradation of other kinds of pesticides or organic pollutants or combined degradation of multiple pollutants to solve the problems of complicated pollutants.

Failure experience (difficulties we met) and our solutions:

1)Because the linear plasmid IGEM provided in distribution had a low purity, using the plasmid construction method recommended by IGEM protocol will cause large quantities of false positive cases in experiment results and interfere greatly with following positive cloning selection. Additionally, because the linear plasmid IGEM provided in distribution cannot reproduce, the quantities used in experiment and times of experiment repetitions were severely restricted.

Solution: Referring to the solutions by other teams before, we gave up using the linear plasmid IGEM provided in distribution and turned to using J04450 plasmid to carry out plasmid expansion and extraction, and gained large amounts of J04450 plasmid structures. By carrying out double enzyme digestion on EcoRI of J04450 and PstI and cutting off segments of mRFP, and replacing with our biology module, we finally successfully constructed plasmid which contained the biology module we designed.

2)Connection of multiple segments, our biology module contains four different sequences, which are F1, F2, F3 and F4 with a total length of over 1800bp. Given current DNA synthetic technology, it is inefficient and takes a long time to synthesize a length of over 1800bp. Moreover, connecting four segments in order to carrier plasmid pSB1C3 also requires four repetitive cloning transformation processes, which takes a lot of time and resources.

Solution: We designed methods of separately synthesizing four segments, which greatly increased synthesizing speed and saved time. Then, we used the enzyme digestion locus pre-designed at the two ends of each segment, and firstly achieved the mutual connection externally. PCR technology without repetitive connections, transformations, cloning selection processes made it possible for us to gain final F1+2+3+4 segments and clone them to pSB1C3 plasmid at a time.

Our submission parts:
 
BBa_K1667005

This part includes two individual DNA domains. Constitutive promoter tunes the expression of downstream opdA gene with further help from RNA thermometer. RNA thermometer provides a temperature sensitive post-transcriptional regulation on opdA gene, which initiate the opdA translation around 32°C. OmpA signal peptide guides the secretion of opdA protein to the outside of host strain. Then opdA enzyme specifically degrades organophosphorus pesticide appeared, through hydrolysis. Upon UV light, RecA(SOS)promoter drives the transcription of downstream ccdB suicide gene, whose protein expression interferes DNA sysnthesis and lead to cell dealth. In this way, we can wipe out our genetic engineered bacteria by giving UV lights under manual control to avoid secondary pollution. Without UV light, RecA promoter won’t be activated, so the normal growth and activity of genetic engineering bacteria will be preserved well to release functional opdA protein under temperature control.

 
More information please see our parts form:
 
Name Type Description Length
BBa_K1667005 DNA OpdA encoding gene with ompA signal peptide 1776