Difference between revisions of "Team:ZJU-China/Design/Toxinmanufacture"

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     <h2 style="color:green;font-size:50p class="p1"x">Toxin manufacture</h2>  
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     <h2 style="color:green;font-size:50px">Toxin manufacture</h2>  
  
  
  
 
 
     <h2 id="p class="p1"os1">Introduction</h2>     
+
     <h2 id="pos1">Introduction</h2>     
 
     <p class="p1">
 
     <p class="p1">
Biological p class="p1"esticides can be divided into two typ class="p1"es: small comp class="p1"ounds and biological macromolecules. On one hand, small comp class="p1"ounds are more p class="p1"rone to be absorbed by termites while more costly to p class="p1"roduce. On the other hand, macromolecules are easier and cheap class="p1"er to p class="p1"roduce whereas sometimes not as effective as small molecules. Hence, to kill termites more efficiently and effectively, we choose both——insecticidal small molecule avermectin and several toxic p class="p1"roteins. We p class="p1"lan to overexp class="p1"ress avermectin in its host <i>Strep class="p1"tomyces avermitilis</i> and exp class="p1"ress three kinds of toxic p class="p1"rotein in <i>Escherichia coli BL21(DE3)</i>. Then we embed the engineered <i>S. avermitilis</i> and <i>E.coli</i> with CNC carrier and fed termites with the CNC embedded bacteria. For more information about CNC, p class="p1"lease go to(CNC的主页面)
+
Biological pesticides can be divided into two types: small compounds and biological macromolecules. On one hand, small compounds are more prone to be absorbed by termites while more costly to produce. On the other hand, macromolecules are easier and cheaper to produce whereas sometimes not as effective as small molecules. Hence, to kill termites more efficiently and effectively, we choose both——insecticidal small molecule avermectin and several toxic proteins. We plan to overexpress avermectin in its host <i>Streptomyces avermitilis</i> and express three kinds of toxic protein in <i>Escherichia coli BL21(DE3)</i>. Then we embed the engineered <i>S. avermitilis</i> and <i>E.coli</i> with CNC carrier and fed termites with the CNC embedded bacteria. For more information about CNC, please go to(CNC的主页面)
 
</p>
 
</p>
  
<h2 id='p class="p1"os2'>Avermectin manufacture</h2>
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<h2 id='pos2'>Avermectin manufacture</h2>
 
<p class="p1">
 
<p class="p1">
Judging that many toxic small comp class="p1"ounds are harmful to human being, we choose avermectin, which is highly sp class="p1"ecific to insect and does no harm to human. For one thing, being a secondary metabolite p class="p1"roduced by <i>Strep class="p1"tomyces avermitilis</i>, avermectin is regulated by an 80kb gene cluster(1), making it difficult to exp class="p1"ress in other standardized strains, for instance, <i>Escherichia coli</i>. For another, the avermectin yield in wild typ class="p1"e<i> S. avermitilis</i> strain is comp class="p1"aratively low(1). Nevertheless, we p class="p1"lan to engineer the wild <i>S. avermitilis</i> to imp class="p1"rove the yield of avermectin, embed the engineered strain with CNC and feed termites with CNC embedded <i>S. avermitilis</i>.
+
Judging that many toxic small compounds are harmful to human being, we choose avermectin, which is highly specific to insect and does no harm to human. For one thing, being a secondary metabolite produced by <i>Streptomyces avermitilis</i>, avermectin is regulated by an 80kb gene cluster(1), making it difficult to express in other standardized strains, for instance, <i>Escherichia coli</i>. For another, the avermectin yield in wild type<i> S. avermitilis</i> strain is comparatively low(1). Nevertheless, we plan to engineer the wild <i>S. avermitilis</i> to improve the yield of avermectin, embed the engineered strain with CNC and feed termites with CNC embedded <i>S. avermitilis</i>.
 
</p>
 
</p>
 
<h3>AVERMECTIN: EFFECTIVE AND BROAD-SPECTRUM PESTICIDE<h3>
 
<h3>AVERMECTIN: EFFECTIVE AND BROAD-SPECTRUM PESTICIDE<h3>
 
<p class="p1">
 
<p class="p1">
For years, p class="p1"eop class="p1"le always adop class="p1"t the organochlorine p class="p1"esticides such as chlordane and mirex to achieve p class="p1"revention and control of termites, but these organochlorine p class="p1"esticides will p class="p1"roduce p class="p1"ollution and p class="p1"otential harm to the environment. Avermectin is a new typ class="p1"e of high efficient biological p class="p1"esticide, which has good control effect to the termites and other p class="p1"ests, and no p class="p1"ollution to the environment(1).  
+
For years, people always adopt the organochlorine pesticides such as chlordane and mirex to achieve prevention and control of termites, but these organochlorine pesticides will produce pollution and potential harm to the environment. Avermectin is a new type of high efficient biological pesticide, which has good control effect to the termites and other pests, and no pollution to the environment(1).  
 
</p>
 
</p>
<h3>HOST OF AVERMECTIN——<i>Strep class="p1"tomyces avermitilis</i></h3>
+
<h3>HOST OF AVERMECTIN——<i>Streptomyces avermitilis</i></h3>
 
 
 
 
 
<p class="p1">
 
<p class="p1">
<i>Strep class="p1"tomyces avermitilis</i>, a soil-dwelling gram-p class="p1"ositive microorganism, is a rich source of numerous secondary metabolites. It’s a kind of Actinomycetes with staghorn-like hyp class="p1"ha (figure 2). Now it has been industrialized to p class="p1"roduce the commercially imp class="p1"ortant antip class="p1"arasitic agent avermectin(2). Early in 2003, the comp class="p1"lete genome of <i>Strep class="p1"tomyces avermitilis</i> had been sequenced(3).
+
<i>Streptomyces avermitilis</i>, a soil-dwelling gram-positive microorganism, is a rich source of numerous secondary metabolites. It’s a kind of Actinomycetes with staghorn-like hypha (figure 2). Now it has been industrialized to produce the commercially important antiparasitic agent avermectin(2). Early in 2003, the complete genome of <i>Streptomyces avermitilis</i> had been sequenced(3).
 
</p>
 
</p>
  
 
<p class="p1">
 
<p class="p1">
In p class="p1"ast years, scientists had been trying to transform gene into <i>S.avermitilis.</i> Until 1989, gene transformation in <i>S.avermitilis </i>was achieved through conjugation(超链接到下面的conjugation) between <i>E.coli strains</i>(eg, <i>s17-1</i>)and <i>S.avermitilis</i>(4)<i>¬. </i>However, the efficiency was limited by the methyl-sp class="p1"ecific restriction system in <i>S.avermitilisi</i>, which show strong restriction to gene methylated in normal <i>E.coli strains</i>(5). Eventually, high efficiency conjugation was achieved till the introduction of methylase-negative donor strain<i> E.coli</i> <i>ET12567</i> (超链接到下面的ET12567介绍)  Now conjugation and strain <i>ET12567</i> has been ubiquitously adop class="p1"ted in the gene transformation of <i>S.avermitilis.</i>
+
In past years, scientists had been trying to transform gene into <i>S.avermitilis.</i> Until 1989, gene transformation in <i>S.avermitilis </i>was achieved through conjugation(超链接到下面的conjugation) between <i>E.coli strains</i>(eg, <i>s17-1</i>)and <i>S.avermitilis</i>(4)<i>¬. </i>However, the efficiency was limited by the methyl-specific restriction system in <i>S.avermitilisi</i>, which show strong restriction to gene methylated in normal <i>E.coli strains</i>(5). Eventually, high efficiency conjugation was achieved till the introduction of methylase-negative donor strain<i> E.coli</i> <i>ET12567</i> (超链接到下面的ET12567介绍)  Now conjugation and strain <i>ET12567</i> has been ubiquitously adopted in the gene transformation of <i>S.avermitilis.</i>
 
</p>
 
</p>
 
 
 
<h3>PROBLEMS AND SOLUTIONS</h3>
 
<h3>PROBLEMS AND SOLUTIONS</h3>
 
<p class="p1">
 
<p class="p1">
Environmentally friendly though avermectin is, the yield of avermectin in wild<i> S. avermitilis</i> doesn’t fulfill our needs. Many efforts have been p class="p1"aid to increase its yield, including develop class="p1"ing genome-minimized hosts, engineering the metabolic network(2), etc. In our p class="p1"roject, we p class="p1"lan to overexp class="p1"ress three genes, <i>frr, orfX, metK</i> in <i>S. avermitilis</i> to imp class="p1"rove the yield of avermectin.
+
Environmentally friendly though avermectin is, the yield of avermectin in wild<i> S. avermitilis</i> doesn’t fulfill our needs. Many efforts have been paid to increase its yield, including developing genome-minimized hosts, engineering the metabolic network(2), etc. In our project, we plan to overexpress three genes, <i>frr, orfX, metK</i> in <i>S. avermitilis</i> to improve the yield of avermectin.
  
  
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<h3>CIRCUITS DESIGN</h3>
 
<h3>CIRCUITS DESIGN</h3>
 
<p class="p1">
 
<p class="p1">
We have constructed three circuits to imp class="p1"rove the yield of avermectin(figure 3).
+
We have constructed three circuits to improve the yield of avermectin(figure 3).
PROMOTER: ermEp class="p1"
+
PROMOTER: ermEp
We chose ermEp class="p1", a strong constitutive p class="p1"romoter, to overexp class="p1"ress the three genes in <i>S.avermitilis</i>. It should be noticed that ermEp class="p1" can only be exp class="p1"ressed in<i> S.avermitilis</i> strains instead of <i>Escherichia coli</i> or any other chassis.  
+
We chose ermEp, a strong constitutive promoter, to overexpress the three genes in <i>S.avermitilis</i>. It should be noticed that ermEp can only be expressed in<i> S.avermitilis</i> strains instead of <i>Escherichia coli</i> or any other chassis.  
 
</p>
 
</p>
 
<h3>BACKBONE: PL96 and PL97</h3>
 
<h3>BACKBONE: PL96 and PL97</h3>
 
<p class="p1">
 
<p class="p1">
` PL96 and PL97 are two high-cop class="p1"y vectors we used to overexp class="p1"ress our target genes. We get these vectors through commercial p class="p1"urchase. These vectors have p class="p1"UC18 and p class="p1"IJ101 rep class="p1"lication origins for high-cop class="p1"y p class="p1"lasmid number in <i>Escherichia coli</i> and <i>S.avermitilis</i>, resp class="p1"ectively, and the oriT (RK2) allows the efficient and convenient p class="p1"lasmid transfer from <i>E.coli</i> to <i>S.avermitilis</i>(6).
+
` PL96 and PL97 are two high-copy vectors we used to overexpress our target genes. We get these vectors through commercial purchase. These vectors have pUC18 and pIJ101 replication origins for high-copy plasmid number in <i>Escherichia coli</i> and <i>S.avermitilis</i>, respectively, and the oriT (RK2) allows the efficient and convenient plasmid transfer from <i>E.coli</i> to <i>S.avermitilis</i>(6).
 
</p>
 
</p>
<p class="p1">To be noticed, we use sp class="p1"ecial antibiotic ap class="p1"aramycin to choose final transformants. And there are ap class="p1"aramycin resistent gene <i>acc</i> in the backbone. </p>
+
<p class="p1">To be noticed, we use special antibiotic aparamycin to choose final transformants. And there are aparamycin resistent gene <i>acc</i> in the backbone. </p>
 
 
 
<h3>EXPRESSION:</h3>
 
<h3>EXPRESSION:</h3>
<p class="p1">In order to<i> </i>construct and exp class="p1"ress the three gene in <i>S.avermitilis</i>, we have adop class="p1"ted two hosts, <i>E.coli</i> <i>DH5α</i>and <i>E.coli</i> <i>ET12567</i>. Then the target vectors are transferred from <i>E.coli</i> <i>ET12567 </i>to <i>S.avermitilis</i> by conjugation.<p class="p1">
+
<p class="p1">In order to<i> </i>construct and express the three gene in <i>S.avermitilis</i>, we have adopted two hosts, <i>E.coli</i> <i>DH5α</i>and <i>E.coli</i> <i>ET12567</i>. Then the target vectors are transferred from <i>E.coli</i> <i>ET12567 </i>to <i>S.avermitilis</i> by conjugation.<p class="p1">
 
 
 
<h3>PRIMARY HOST: <i>E.coli</i> <i>DH5α</i></h3>
 
<h3>PRIMARY HOST: <i>E.coli</i> <i>DH5α</i></h3>
<p class="p1"> As usual, we use <i>E.coli</i> <i>DH5α</i> to get p class="p1"lenty of recombinants in high quality and quantity. </p>
+
<p class="p1"> As usual, we use <i>E.coli</i> <i>DH5α</i> to get plenty of recombinants in high quality and quantity. </p>
 
 
 
<h3>INTERMEDIA HOST: <i>E.coli</i> <i>ET12567</i></h3>
 
<h3>INTERMEDIA HOST: <i>E.coli</i> <i>ET12567</i></h3>
<p class="p1"><i>E.coli</i> <i>ET12567 </i>is a methylase-negative donor strain first used by MacNeil in 1988(7). And we use <i>E.coli</i> <i>ET12567</i> to demethylation the recombinants to better suit the methyl-sp class="p1"ecific restriction system in <i>S.avermitilisi.</i>(超链接到上面的介绍页面)
+
<p class="p1"><i>E.coli</i> <i>ET12567 </i>is a methylase-negative donor strain first used by MacNeil in 1988(7). And we use <i>E.coli</i> <i>ET12567</i> to demethylation the recombinants to better suit the methyl-specific restriction system in <i>S.avermitilisi.</i>(超链接到上面的介绍页面)
 
 
 
 
 
<h3>CONJUGATION:</h3>
 
<h3>CONJUGATION:</h3>
<p class="p1">Bacterial conjugation is the transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells. During conjugation the donor cell p class="p1"rovides a conjugative or mobilizable genetic element that is most often a p class="p1"lasmid or transp class="p1"oson(8). In laboratories, successful transfers have been rep class="p1"orted from bacteria to yeast(9), p class="p1"lants(10), mammalian cells(11), etc.
+
<p class="p1">Bacterial conjugation is the transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells. During conjugation the donor cell provides a conjugative or mobilizable genetic element that is most often a plasmid or transposon(8). In laboratories, successful transfers have been reported from bacteria to yeast(9), plants(10), mammalian cells(11), etc.
In our p class="p1"roject, we use the conjugation between <i>E.coli</i> <i>ET12567</i> and <i>S.avermitilisi</i> to overexp class="p1"ress three target genes.  
+
In our project, we use the conjugation between <i>E.coli</i> <i>ET12567</i> and <i>S.avermitilisi</i> to overexpress three target genes.  
 
</p>
 
</p>
<p class="p1">To see the results of exp class="p1"ression and toxic exp class="p1"eriment on termites, p class="p1"lease go to (results页面) </p>
+
<p class="p1">To see the results of expression and toxic experiment on termites, please go to (results页面) </p>
  
 
<h3>CIRCUITS CONSTRUCTION</h3>
 
<h3>CIRCUITS CONSTRUCTION</h3>
 
<p class="p1"> STEP ONE: PCR</p>
 
<p class="p1"> STEP ONE: PCR</p>
<p class="p1">We amp class="p1"lify the target gene from the genome of <i>S.avermitilisi</i> by PCR. The p class="p1"rimer and PCR p class="p1"rogram can be seen in our biobrick p class="p1"ages(超链接到biobrick).</p>
+
<p class="p1">We amplify the target gene from the genome of <i>S.avermitilisi</i> by PCR. The primer and PCR program can be seen in our biobrick pages(超链接到biobrick).</p>
 
<p class="p1">STEP TWO: TA CLONING</p>
 
<p class="p1">STEP TWO: TA CLONING</p>
<p class="p1">We use TA cloning to efficiently clone the PCR p class="p1"roducts. In TA cloning, we use p class="p1"MD19-T Vector, a vector transformed from p class="p1"UC19 vector, to imp class="p1"rove the efficiency of digestion and connection. As a result, we get three recombinant vectors of target genes and p class="p1"MD19-T.</p>
+
<p class="p1">We use TA cloning to efficiently clone the PCR products. In TA cloning, we use pMD19-T Vector, a vector transformed from pUC19 vector, to improve the efficiency of digestion and connection. As a result, we get three recombinant vectors of target genes and pMD19-T.</p>
 
<p class="p1">STEP THREE: DIGESTION AND CONNECTION</p>
 
<p class="p1">STEP THREE: DIGESTION AND CONNECTION</p>
<p class="p1">We digest the three recombinants and backbone PL96 with restriction enzymes NdeI, XbaI, then connect the fragments and backbone. Similarly, we use NdeI, HindⅢ to digest the three recombinants and backbone PL97 and connect the corresp class="p1"onding p class="p1"roduct. Then we get the target p class="p1"lasmids.</p>
+
<p class="p1">We digest the three recombinants and backbone PL96 with restriction enzymes NdeI, XbaI, then connect the fragments and backbone. Similarly, we use NdeI, HindⅢ to digest the three recombinants and backbone PL97 and connect the corresponding product. Then we get the target plasmids.</p>
<p class="p1">For more detailed p class="p1"rotocols, p class="p1"lease go to(超链接到p class="p1"rotocol). </p>
+
<p class="p1">For more detailed protocols, please go to(超链接到protocol). </p>
<h2 id="p class="p1"os2">Toxic p class="p1"rotein manufacture</h2>
+
<h2 id="pos2">Toxic protein manufacture</h2>
 
<p class="p1">
 
<p class="p1">
Cellulose has sp class="p1"ecific structure feature, based on which we successfully achieve self-assembly between CNCs and bacteria in aqueous solution driven by multivalent interactions esp class="p1"ecially the multip class="p1"le hydrogen bonds. This p class="p1"age will discuss the main theories and methods of CNC carriers.  
+
Cellulose has specific structure feature, based on which we successfully achieve self-assembly between CNCs and bacteria in aqueous solution driven by multivalent interactions especially the multiple hydrogen bonds. This page will discuss the main theories and methods of CNC carriers.  
 
</p>
 
</p>
 
<h3>Structure of cellulose</h3>
 
<h3>Structure of cellulose</h3>
 
<p class="p1">
 
<p class="p1">
In order to kill the termites, we have chosen four typ class="p1"es of insecticidal toxic p class="p1"roteins, resp class="p1"ectively Tc p class="p1"rotein tcdA1, tcdB1, bt-like Plu0840 and enterotoxin-like Plu1537, from <i>Photorhabdus luminescens TT01, </i>a bacterium of native toxin storehouse. Then we cloned these genes from the genome of <i>TT01</i>, constructed corresp class="p1"onding vectors, successfully exp class="p1"ressed these p class="p1"roteins in <i>Escherichia coli BL21(DE3) </i>and fed the termites with the raw engineered BL21 and that embedded with CNC. For more information about CNC, p class="p1"lease go to(CNC的主页面)
+
In order to kill the termites, we have chosen four types of insecticidal toxic proteins, respectively Tc protein tcdA1, tcdB1, bt-like Plu0840 and enterotoxin-like Plu1537, from <i>Photorhabdus luminescens TT01, </i>a bacterium of native toxin storehouse. Then we cloned these genes from the genome of <i>TT01</i>, constructed corresponding vectors, successfully expressed these proteins in <i>Escherichia coli BL21(DE3) </i>and fed the termites with the raw engineered BL21 and that embedded with CNC. For more information about CNC, please go to(CNC的主页面)
 
</p>
 
</p>
 
 
 
<h3>HOST OF TOXIN -- <i>Photorhabdus luminescens</i></h3>
 
<h3>HOST OF TOXIN -- <i>Photorhabdus luminescens</i></h3>
<p class="p1"><i>Photorhabdus luminescens</i>, one kind of gram-negative bacteria, is cap class="p1"able of p class="p1"roducing and releasing a variety of insecticidal and bactericidal toxins. Living in symbiosis with nematodes, “the bacteria are released and start to p class="p1"roduce toxins that eventually kill the insect after insect larvae are invaded by nematodes, thereby generating a food resource for bacteria and nematodes”(12).</p>
+
<p class="p1"><i>Photorhabdus luminescens</i>, one kind of gram-negative bacteria, is capable of producing and releasing a variety of insecticidal and bactericidal toxins. Living in symbiosis with nematodes, “the bacteria are released and start to produce toxins that eventually kill the insect after insect larvae are invaded by nematodes, thereby generating a food resource for bacteria and nematodes”(12).</p>
 
<p class="p1">
 
<p class="p1">
The whole genome of strain TT01, which has been sequenced in 2003, is p class="p1"redicted to encode 4839 kinds of p class="p1"rotein(12). And many of them are toxic p class="p1"roteins, most of which remain functionally unclear. Although they are toxic to insects and many other bacteria, <i>Photorhabdus luminescens</i> belongs to Risk Group class="p1" 1 according to DSMZ (Deutsche Sammlung von Mikroorganismen und Zellkulturen) and has no toxic effect on human being at all. “More than 50 years of field ap class="p1"p class="p1"lication of nematodes for controlling insect p class="p1"ests also showed that EN and their symbiotic bacteria (<i>Photorhabdus luminescens</i>) are safe to human” and “EN-based bio-p class="p1"esticides were exemp class="p1"ted from registration in many countries, including USA and all Europ class="p1"ean countries”(13).  
+
The whole genome of strain TT01, which has been sequenced in 2003, is predicted to encode 4839 kinds of protein(12). And many of them are toxic proteins, most of which remain functionally unclear. Although they are toxic to insects and many other bacteria, <i>Photorhabdus luminescens</i> belongs to Risk Group 1 according to DSMZ (Deutsche Sammlung von Mikroorganismen und Zellkulturen) and has no toxic effect on human being at all. “More than 50 years of field application of nematodes for controlling insect pests also showed that EN and their symbiotic bacteria (<i>Photorhabdus luminescens</i>) are safe to human” and “EN-based bio-pesticides were exempted from registration in many countries, including USA and all European countries”(13).  
 
</p>
 
</p>
 
<h3>TOXIN PROTEIN IN <i>P. luminescens TT01</i></h3>
 
<h3>TOXIN PROTEIN IN <i>P. luminescens TT01</i></h3>
 
<p class="p1">
 
<p class="p1">
Numerous toxins as there are in the genome of <i>P. luminescens TT01</i>, many of them have never been studied. Moreover, many small-molecule toxins are regulated by comp class="p1"lex gene cluster, which makes it difficult to exp class="p1"ress in other standardized hosts, for instance <i>Escherichia coli. </i>Hence, on account of cost and safety, we chose four typ class="p1"es of single-gene regulated toxic p class="p1"rotein, tcdA1, tcdB1, Plu0840 and Plu1537,  instead of small molecules because the former is easier to manip class="p1"ulate and less risky to the environment. </p>
+
Numerous toxins as there are in the genome of <i>P. luminescens TT01</i>, many of them have never been studied. Moreover, many small-molecule toxins are regulated by complex gene cluster, which makes it difficult to express in other standardized hosts, for instance <i>Escherichia coli. </i>Hence, on account of cost and safety, we chose four types of single-gene regulated toxic protein, tcdA1, tcdB1, Plu0840 and Plu1537,  instead of small molecules because the former is easier to manipulate and less risky to the environment. </p>
 
<h3>tcdA1: PORE FORMING PROTEIN of Tc TOXIN FAMILY</h3>
 
<h3>tcdA1: PORE FORMING PROTEIN of Tc TOXIN FAMILY</h3>
<p class="p1">The most remarkable toxin family till now is the Tc family, which are widely distributed among different gram-negative and gram-p class="p1"ositive bacteria. </p>
+
<p class="p1">The most remarkable toxin family till now is the Tc family, which are widely distributed among different gram-negative and gram-positive bacteria. </p>
<p class="p1">Tcs are comp class="p1"osed of TcA, TcB, and TcC. TcA is sup class="p1"p class="p1"osed to p class="p1"erforate the membrane by forming channel outside-in and translocating the toxic enzymes into the host. Meanwhile the TcB and TcC coop class="p1"erate with a syringe-like mechanism during membrane insertion(14).</p>
+
<p class="p1">Tcs are composed of TcA, TcB, and TcC. TcA is supposed to perforate the membrane by forming channel outside-in and translocating the toxic enzymes into the host. Meanwhile the TcB and TcC cooperate with a syringe-like mechanism during membrane insertion(14).</p>
<p class="p1">In a 2008 study, researchers exp class="p1"ressed tcdA1 and tcdB1 in <i><i>Enterobacter cloacae </i> </i>and fed the termites with <i>E. cloacae</i> to control termites(15). Insp class="p1"ired by their exp class="p1"eriment, we chose to exp class="p1"ress tcdA1 (Unip class="p1"rot: Q7N7Y9_PHOLL) and tcdB1(Unip class="p1"rot: Q7N7Z0_PHOLL) to kill termites. For more details, p class="p1"lease go to p class="p1"arts 的网页链接</p>
+
<p class="p1">In a 2008 study, researchers expressed tcdA1 and tcdB1 in <i><i>Enterobacter cloacae </i> </i>and fed the termites with <i>E. cloacae</i> to control termites(15). Inspired by their experiment, we chose to express tcdA1 (Uniprot: Q7N7Y9_PHOLL) and tcdB1(Uniprot: Q7N7Z0_PHOLL) to kill termites. For more details, please go to parts 的网页链接</p>
 
<h3>Plu1537: Bt HOMOLOGOUS TOXIC PROTEIN</h3>
 
<h3>Plu1537: Bt HOMOLOGOUS TOXIC PROTEIN</h3>
  
 
<p class="p1">The exact function of Plu1537 is still unclear, but a research in 2009 indicated that Plu1537 “had insecticidal activity against Galleria larvae”(16). </p>
 
<p class="p1">The exact function of Plu1537 is still unclear, but a research in 2009 indicated that Plu1537 “had insecticidal activity against Galleria larvae”(16). </p>
<p class="p1">Judging that the Plu1537 p class="p1"rotein has 30% p class="p1"redicted amino acid sequence similarity to a 13.6 kDa insecticidal crystal p class="p1"rotein cry34Ab1(figure 12) in<i> Bacillus thuringiensis </i>(Unip class="p1"rot: Q939T0_BACTU), which belongs to Bt crystal p class="p1"rotein family, it may have similar toxic effect with cry34Ab1 Bt p class="p1"rotein.</p>
+
<p class="p1">Judging that the Plu1537 protein has 30% predicted amino acid sequence similarity to a 13.6 kDa insecticidal crystal protein cry34Ab1(figure 12) in<i> Bacillus thuringiensis </i>(Uniprot: Q939T0_BACTU), which belongs to Bt crystal protein family, it may have similar toxic effect with cry34Ab1 Bt protein.</p>
<p class="p1">Bt p class="p1"rotein may be the most well-known toxic p class="p1"rotein till now. It is widely used in transgene p class="p1"lants to kill the larvae of worm. It also “interacts with membranes to form p class="p1"ores”(17). And there are abundant evidences to ensure the safety of Bt p class="p1"rotein(更详细?). </p>
+
<p class="p1">Bt protein may be the most well-known toxic protein till now. It is widely used in transgene plants to kill the larvae of worm. It also “interacts with membranes to form pores”(17). And there are abundant evidences to ensure the safety of Bt protein(更详细?). </p>
<p class="p1">We have successfully cloned the<i> p class="p1"lu1537</i> gene and exp class="p1"ressed the Plu1537 toxin p class="p1"rotein in<i> E.coli</i> <i>BL21(DE3)</i>, for more details, p class="p1"lease go to </p>
+
<p class="p1">We have successfully cloned the<i> plu1537</i> gene and expressed the Plu1537 toxin protein in<i> E.coli</i> <i>BL21(DE3)</i>, for more details, please go to </p>
  
 
<h3>Plu0840: ENTEROTOXIN Ast HOMOLOGOUS PROTEIN</h3>
 
<h3>Plu0840: ENTEROTOXIN Ast HOMOLOGOUS PROTEIN</h3>
 
<p class="p1">The exact function of Plu0840 is also unclear. A 2007 study confirmed that Plu0840 had weak oral toxicity against two kinds of moth (<i>S. litura and S. exigua</i>)(13). </p>
 
<p class="p1">The exact function of Plu0840 is also unclear. A 2007 study confirmed that Plu0840 had weak oral toxicity against two kinds of moth (<i>S. litura and S. exigua</i>)(13). </p>
<p class="p1">Sequence analysis showed that the p class="p1"lu0840 in the P. luminescens TT01 genome has 55% sequence identity with an enterotoxin Ast from Aeromonas hydrop class="p1"hila, therefore may p class="p1"lay a similar role. (see figure 13)</p>
+
<p class="p1">Sequence analysis showed that the plu0840 in the P. luminescens TT01 genome has 55% sequence identity with an enterotoxin Ast from Aeromonas hydrophila, therefore may play a similar role. (see figure 13)</p>
<p class="p1">In 2001, researchers studied the function of enterotoxin Ast from Aeromonas hydrop class="p1"hila, concluded that it p class="p1"layed an imp class="p1"ortant role in A. hydrop class="p1"hila-induced gastroenteritis in a mouse model(18). </p>
+
<p class="p1">In 2001, researchers studied the function of enterotoxin Ast from Aeromonas hydrophila, concluded that it played an important role in A. hydrophila-induced gastroenteritis in a mouse model(18). </p>
<p class="p1"> We have successfully cloned the <i>p class="p1"lu0840</i> gene and exp class="p1"ressed he Plu0840 toxin p class="p1"rotein in<i> E.coli</i> <i>BL21(DE3)</i>, for more details, p class="p1"lease go to</p>
+
<p class="p1"> We have successfully cloned the <i>plu0840</i> gene and expressed he Plu0840 toxin protein in<i> E.coli</i> <i>BL21(DE3)</i>, for more details, please go to</p>
 
<h3>CIRCUITS DESIGN</h3>
 
<h3>CIRCUITS DESIGN</h3>
<p class="p1"> As disp class="p1"layed in figure 14, we have constructed three devices to exp class="p1"ress corresp class="p1"onding toxic p class="p1"roteins, p class="p1"lu1537 (BBa_K1668010), p class="p1"lu0840 (BBa_K1668009) and tcdA1 (BBa_K1668008)
+
<p class="p1"> As displayed in figure 14, we have constructed three devices to express corresponding toxic proteins, plu1537 (BBa_K1668010), plu0840 (BBa_K1668009) and tcdA1 (BBa_K1668008)
(注:p class="p1"arts name超链接到p class="p1"arts页面
+
(注:parts name超链接到parts页面
 
</p>
 
</p>
  
 
<ul>
 
<ul>
<li> <a href="http class="p1"://parts.igem.org/Part:BBa_K1668010"  > BBa_K1668010 </a>  </li>
+
<li> <a href="http://parts.igem.org/Part:BBa_K1668010"  > BBa_K1668010 </a>  </li>
<li> <a href="http class="p1"://parts.igem.org/Part:BBa_K1668009"  > BBa_K1668009 </a>  </li>
+
<li> <a href="http://parts.igem.org/Part:BBa_K1668009"  > BBa_K1668009 </a>  </li>
<li> <a href="http class="p1"://parts.igem.org/Part:BBa_K1668008"  > BBa_K1668008 </a>  </li>
+
<li> <a href="http://parts.igem.org/Part:BBa_K1668008"  > BBa_K1668008 </a>  </li>
<li> <a href="http class="p1"://parts.igem.org/Part: BBa_I0500"    > BBa_I0500 </a>  </li>
+
<li> <a href="http://parts.igem.org/Part: BBa_I0500"    > BBa_I0500 </a>  </li>
<li> <a href="http class="p1"://parts.igem.org/Part: BBa_B0034"    > BBa_B0034 </a>  </li>
+
<li> <a href="http://parts.igem.org/Part: BBa_B0034"    > BBa_B0034 </a>  </li>
<li> <a href="http class="p1"://parts.igem.org/Part:BBa_K1668011)"  > BBa_K1668011 </a>  </li>
+
<li> <a href="http://parts.igem.org/Part:BBa_K1668011)"  > BBa_K1668011 </a>  </li>
 
</ul>
 
</ul>
  
  
<h3>PROMOTER: p class="p1"Bad(BBa_I0500)</h3>
+
<h3>PROMOTER: pBad(BBa_I0500)</h3>
  
<p class="p1">We chose arabinose inducible p class="p1"romoter p class="p1"Bad (BBa_I0500) because it’s not only of medium strength with arabinose up class="p1" to certain concentration, but also have little leakage. Moreover, the p class="p1"Bad p class="p1"romoter is rep class="p1"ressed by glucose, giving the exp class="p1"ression more controllability. In order to p class="p1"romote exp class="p1"ression, we chose one of the strongest RBS in Parts Registry (BBa_B0034). </p>
+
<p class="p1">We chose arabinose inducible promoter pBad (BBa_I0500) because it’s not only of medium strength with arabinose up to certain concentration, but also have little leakage. Moreover, the pBad promoter is repressed by glucose, giving the expression more controllability. In order to promote expression, we chose one of the strongest RBS in Parts Registry (BBa_B0034). </p>
<p class="p1">BACOBONE: p class="p1"SB1C3</p>
+
<p class="p1">BACOBONE: pSB1C3</p>
 
<h3>EXPRESSION:</h3>
 
<h3>EXPRESSION:</h3>
<p class="p1">We adop class="p1"ted tandem exp class="p1"ression of toxin and rep class="p1"orter mCherry (BBa_K1668011) to roughly judge whether toxin is exp class="p1"ressed. </p>
+
<p class="p1">We adopted tandem expression of toxin and reporter mCherry (BBa_K1668011) to roughly judge whether toxin is expressed. </p>
<p class="p1">We use <i>E.coli</i> <i>DH5α</i> to get p class="p1"lenty recombinants in high quality and quantity. Then we transform the p class="p1"ositive recombinants into <i>E.coli</i> <i>BL21(DE3)</i> for high-quality exp class="p1"ression.</p>
+
<p class="p1">We use <i>E.coli</i> <i>DH5α</i> to get plenty recombinants in high quality and quantity. Then we transform the positive recombinants into <i>E.coli</i> <i>BL21(DE3)</i> for high-quality expression.</p>
<p class="p1">To see the results of exp class="p1"ression and toxic exp class="p1"eriment on termites, p class="p1"lease go to (results页面)</p>
+
<p class="p1">To see the results of expression and toxic experiment on termites, please go to (results页面)</p>
  
 
<h3>CIRCUITS CONSTRUCTION</h3>
 
<h3>CIRCUITS CONSTRUCTION</h3>
 
<p class="p1">STEP ONE: PCR</p>
 
<p class="p1">STEP ONE: PCR</p>
<p class="p1">We amp class="p1"lify the target gene from the genome of <i>S.avermitilisi</i> by PCR. We also clone the arabinose inducible p class="p1"romoter p class="p1"Bad from Part Registry. The p class="p1"rimer and PCR p class="p1"rogram can be seen in our biobrick p class="p1"ages(超链接到biobrick).</p>
+
<p class="p1">We amplify the target gene from the genome of <i>S.avermitilisi</i> by PCR. We also clone the arabinose inducible promoter pBad from Part Registry. The primer and PCR program can be seen in our biobrick pages(超链接到biobrick).</p>
 
<p class="p1"> STEP TWO: BACKBONE DIGESTION</p>
 
<p class="p1"> STEP TWO: BACKBONE DIGESTION</p>
<p class="p1"> We digest the p class="p1"art BBa_J06702, mCherry with RBS in front and double terminator behind, with restriction enzyme XbaI to make a linearized backbone. </p>
+
<p class="p1"> We digest the part BBa_J06702, mCherry with RBS in front and double terminator behind, with restriction enzyme XbaI to make a linearized backbone. </p>
 
<p class="p1">STEP THREE: SCARLESS ASSEMBLY</p>
 
<p class="p1">STEP THREE: SCARLESS ASSEMBLY</p>
<p class="p1"> We use the MultiS_one step class="p1" cloning kit of Vazyme comp class="p1"any to assemble the target gene and backbone. The mechanism is showed in figure 15. </p>
+
<p class="p1"> We use the MultiS_one step cloning kit of Vazyme company to assemble the target gene and backbone. The mechanism is showed in figure 15. </p>
<p class="p1">For more detailes about scarless assembly and any other p class="p1"rotocols, p class="p1"lease go to(超链接到p class="p1"rotocol)</p>
+
<p class="p1">For more detailes about scarless assembly and any other protocols, please go to(超链接到protocol)</p>
  
  
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<p class="p1"> 16. M. Li et al., MOL BIOL REP 36, 785 (2009).                                  </p>
 
<p class="p1"> 16. M. Li et al., MOL BIOL REP 36, 785 (2009).                                  </p>
 
<p class="p1"> 17. M. S. Kelker et al., PLOS ONE 9, (2014).                                    </p>
 
<p class="p1"> 17. M. S. Kelker et al., PLOS ONE 9, (2014).                                    </p>
<p class="p1"> 18. J. Sha, E. V. Kozlova, A. K. Chop class="p1"ra, INFECT IMMUN 70, 1924 (2002).          </p>
+
<p class="p1"> 18. J. Sha, E. V. Kozlova, A. K. Chopra, INFECT IMMUN 70, 1924 (2002).          </p>
 
 
 
 
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Revision as of 17:17, 14 September 2015

Toxin manufacture

Introduction

Biological pesticides can be divided into two types: small compounds and biological macromolecules. On one hand, small compounds are more prone to be absorbed by termites while more costly to produce. On the other hand, macromolecules are easier and cheaper to produce whereas sometimes not as effective as small molecules. Hence, to kill termites more efficiently and effectively, we choose both——insecticidal small molecule avermectin and several toxic proteins. We plan to overexpress avermectin in its host Streptomyces avermitilis and express three kinds of toxic protein in Escherichia coli BL21(DE3). Then we embed the engineered S. avermitilis and E.coli with CNC carrier and fed termites with the CNC embedded bacteria. For more information about CNC, please go to(CNC的主页面)

Avermectin manufacture

Judging that many toxic small compounds are harmful to human being, we choose avermectin, which is highly specific to insect and does no harm to human. For one thing, being a secondary metabolite produced by Streptomyces avermitilis, avermectin is regulated by an 80kb gene cluster(1), making it difficult to express in other standardized strains, for instance, Escherichia coli. For another, the avermectin yield in wild type S. avermitilis strain is comparatively low(1). Nevertheless, we plan to engineer the wild S. avermitilis to improve the yield of avermectin, embed the engineered strain with CNC and feed termites with CNC embedded S. avermitilis.

AVERMECTIN: EFFECTIVE AND BROAD-SPECTRUM PESTICIDE

For years, people always adopt the organochlorine pesticides such as chlordane and mirex to achieve prevention and control of termites, but these organochlorine pesticides will produce pollution and potential harm to the environment. Avermectin is a new type of high efficient biological pesticide, which has good control effect to the termites and other pests, and no pollution to the environment(1).

HOST OF AVERMECTIN——Streptomyces avermitilis

Streptomyces avermitilis, a soil-dwelling gram-positive microorganism, is a rich source of numerous secondary metabolites. It’s a kind of Actinomycetes with staghorn-like hypha (figure 2). Now it has been industrialized to produce the commercially important antiparasitic agent avermectin(2). Early in 2003, the complete genome of Streptomyces avermitilis had been sequenced(3).

In past years, scientists had been trying to transform gene into S.avermitilis. Until 1989, gene transformation in S.avermitilis was achieved through conjugation(超链接到下面的conjugation) between E.coli strains(eg, s17-1)and S.avermitilis(4)¬. However, the efficiency was limited by the methyl-specific restriction system in S.avermitilisi, which show strong restriction to gene methylated in normal E.coli strains(5). Eventually, high efficiency conjugation was achieved till the introduction of methylase-negative donor strain E.coli ET12567 (超链接到下面的ET12567介绍) Now conjugation and strain ET12567 has been ubiquitously adopted in the gene transformation of S.avermitilis.

PROBLEMS AND SOLUTIONS

Environmentally friendly though avermectin is, the yield of avermectin in wild S. avermitilis doesn’t fulfill our needs. Many efforts have been paid to increase its yield, including developing genome-minimized hosts, engineering the metabolic network(2), etc. In our project, we plan to overexpress three genes, frr, orfX, metK in S. avermitilis to improve the yield of avermectin.

CIRCUITS DESIGN

We have constructed three circuits to improve the yield of avermectin(figure 3). PROMOTER: ermEp We chose ermEp, a strong constitutive promoter, to overexpress the three genes in S.avermitilis. It should be noticed that ermEp can only be expressed in S.avermitilis strains instead of Escherichia coli or any other chassis.

BACKBONE: PL96 and PL97

` PL96 and PL97 are two high-copy vectors we used to overexpress our target genes. We get these vectors through commercial purchase. These vectors have pUC18 and pIJ101 replication origins for high-copy plasmid number in Escherichia coli and S.avermitilis, respectively, and the oriT (RK2) allows the efficient and convenient plasmid transfer from E.coli to S.avermitilis(6).

To be noticed, we use special antibiotic aparamycin to choose final transformants. And there are aparamycin resistent gene acc in the backbone.

EXPRESSION:

In order to construct and express the three gene in S.avermitilis, we have adopted two hosts, E.coli DH5αand E.coli ET12567. Then the target vectors are transferred from E.coli ET12567 to S.avermitilis by conjugation.

PRIMARY HOST: E.coli DH5α

As usual, we use E.coli DH5α to get plenty of recombinants in high quality and quantity.

INTERMEDIA HOST: E.coli ET12567

E.coli ET12567 is a methylase-negative donor strain first used by MacNeil in 1988(7). And we use E.coli ET12567 to demethylation the recombinants to better suit the methyl-specific restriction system in S.avermitilisi.(超链接到上面的介绍页面)

CONJUGATION:

Bacterial conjugation is the transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells. During conjugation the donor cell provides a conjugative or mobilizable genetic element that is most often a plasmid or transposon(8). In laboratories, successful transfers have been reported from bacteria to yeast(9), plants(10), mammalian cells(11), etc. In our project, we use the conjugation between E.coli ET12567 and S.avermitilisi to overexpress three target genes.

To see the results of expression and toxic experiment on termites, please go to (results页面)

CIRCUITS CONSTRUCTION

STEP ONE: PCR

We amplify the target gene from the genome of S.avermitilisi by PCR. The primer and PCR program can be seen in our biobrick pages(超链接到biobrick).

STEP TWO: TA CLONING

We use TA cloning to efficiently clone the PCR products. In TA cloning, we use pMD19-T Vector, a vector transformed from pUC19 vector, to improve the efficiency of digestion and connection. As a result, we get three recombinant vectors of target genes and pMD19-T.

STEP THREE: DIGESTION AND CONNECTION

We digest the three recombinants and backbone PL96 with restriction enzymes NdeI, XbaI, then connect the fragments and backbone. Similarly, we use NdeI, HindⅢ to digest the three recombinants and backbone PL97 and connect the corresponding product. Then we get the target plasmids.

For more detailed protocols, please go to(超链接到protocol).

Toxic protein manufacture

Cellulose has specific structure feature, based on which we successfully achieve self-assembly between CNCs and bacteria in aqueous solution driven by multivalent interactions especially the multiple hydrogen bonds. This page will discuss the main theories and methods of CNC carriers.

Structure of cellulose

In order to kill the termites, we have chosen four types of insecticidal toxic proteins, respectively Tc protein tcdA1, tcdB1, bt-like Plu0840 and enterotoxin-like Plu1537, from Photorhabdus luminescens TT01, a bacterium of native toxin storehouse. Then we cloned these genes from the genome of TT01, constructed corresponding vectors, successfully expressed these proteins in Escherichia coli BL21(DE3) and fed the termites with the raw engineered BL21 and that embedded with CNC. For more information about CNC, please go to(CNC的主页面)

HOST OF TOXIN -- Photorhabdus luminescens

Photorhabdus luminescens, one kind of gram-negative bacteria, is capable of producing and releasing a variety of insecticidal and bactericidal toxins. Living in symbiosis with nematodes, “the bacteria are released and start to produce toxins that eventually kill the insect after insect larvae are invaded by nematodes, thereby generating a food resource for bacteria and nematodes”(12).

The whole genome of strain TT01, which has been sequenced in 2003, is predicted to encode 4839 kinds of protein(12). And many of them are toxic proteins, most of which remain functionally unclear. Although they are toxic to insects and many other bacteria, Photorhabdus luminescens belongs to Risk Group 1 according to DSMZ (Deutsche Sammlung von Mikroorganismen und Zellkulturen) and has no toxic effect on human being at all. “More than 50 years of field application of nematodes for controlling insect pests also showed that EN and their symbiotic bacteria (Photorhabdus luminescens) are safe to human” and “EN-based bio-pesticides were exempted from registration in many countries, including USA and all European countries”(13).

TOXIN PROTEIN IN P. luminescens TT01

Numerous toxins as there are in the genome of P. luminescens TT01, many of them have never been studied. Moreover, many small-molecule toxins are regulated by complex gene cluster, which makes it difficult to express in other standardized hosts, for instance Escherichia coli. Hence, on account of cost and safety, we chose four types of single-gene regulated toxic protein, tcdA1, tcdB1, Plu0840 and Plu1537, instead of small molecules because the former is easier to manipulate and less risky to the environment.

tcdA1: PORE FORMING PROTEIN of Tc TOXIN FAMILY

The most remarkable toxin family till now is the Tc family, which are widely distributed among different gram-negative and gram-positive bacteria.

Tcs are composed of TcA, TcB, and TcC. TcA is supposed to perforate the membrane by forming channel outside-in and translocating the toxic enzymes into the host. Meanwhile the TcB and TcC cooperate with a syringe-like mechanism during membrane insertion(14).

In a 2008 study, researchers expressed tcdA1 and tcdB1 in Enterobacter cloacae and fed the termites with E. cloacae to control termites(15). Inspired by their experiment, we chose to express tcdA1 (Uniprot: Q7N7Y9_PHOLL) and tcdB1(Uniprot: Q7N7Z0_PHOLL) to kill termites. For more details, please go to parts 的网页链接

Plu1537: Bt HOMOLOGOUS TOXIC PROTEIN

The exact function of Plu1537 is still unclear, but a research in 2009 indicated that Plu1537 “had insecticidal activity against Galleria larvae”(16).

Judging that the Plu1537 protein has 30% predicted amino acid sequence similarity to a 13.6 kDa insecticidal crystal protein cry34Ab1(figure 12) in Bacillus thuringiensis (Uniprot: Q939T0_BACTU), which belongs to Bt crystal protein family, it may have similar toxic effect with cry34Ab1 Bt protein.

Bt protein may be the most well-known toxic protein till now. It is widely used in transgene plants to kill the larvae of worm. It also “interacts with membranes to form pores”(17). And there are abundant evidences to ensure the safety of Bt protein(更详细?).

We have successfully cloned the plu1537 gene and expressed the Plu1537 toxin protein in E.coli BL21(DE3), for more details, please go to

Plu0840: ENTEROTOXIN Ast HOMOLOGOUS PROTEIN

The exact function of Plu0840 is also unclear. A 2007 study confirmed that Plu0840 had weak oral toxicity against two kinds of moth (S. litura and S. exigua)(13).

Sequence analysis showed that the plu0840 in the P. luminescens TT01 genome has 55% sequence identity with an enterotoxin Ast from Aeromonas hydrophila, therefore may play a similar role. (see figure 13)

In 2001, researchers studied the function of enterotoxin Ast from Aeromonas hydrophila, concluded that it played an important role in A. hydrophila-induced gastroenteritis in a mouse model(18).

We have successfully cloned the plu0840 gene and expressed he Plu0840 toxin protein in E.coli BL21(DE3), for more details, please go to

CIRCUITS DESIGN

As displayed in figure 14, we have constructed three devices to express corresponding toxic proteins, plu1537 (BBa_K1668010), plu0840 (BBa_K1668009) and tcdA1 (BBa_K1668008) (注:parts name超链接到parts页面

PROMOTER: pBad(BBa_I0500)

We chose arabinose inducible promoter pBad (BBa_I0500) because it’s not only of medium strength with arabinose up to certain concentration, but also have little leakage. Moreover, the pBad promoter is repressed by glucose, giving the expression more controllability. In order to promote expression, we chose one of the strongest RBS in Parts Registry (BBa_B0034).

BACOBONE: pSB1C3

EXPRESSION:

We adopted tandem expression of toxin and reporter mCherry (BBa_K1668011) to roughly judge whether toxin is expressed.

We use E.coli DH5α to get plenty recombinants in high quality and quantity. Then we transform the positive recombinants into E.coli BL21(DE3) for high-quality expression.

To see the results of expression and toxic experiment on termites, please go to (results页面)

CIRCUITS CONSTRUCTION

STEP ONE: PCR

We amplify the target gene from the genome of S.avermitilisi by PCR. We also clone the arabinose inducible promoter pBad from Part Registry. The primer and PCR program can be seen in our biobrick pages(超链接到biobrick).

STEP TWO: BACKBONE DIGESTION

We digest the part BBa_J06702, mCherry with RBS in front and double terminator behind, with restriction enzyme XbaI to make a linearized backbone.

STEP THREE: SCARLESS ASSEMBLY

We use the MultiS_one step cloning kit of Vazyme company to assemble the target gene and backbone. The mechanism is showed in figure 15.

For more detailes about scarless assembly and any other protocols, please go to(超链接到protocol)

Reference

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4. P. MAZODIER, R. PETTER, C. THOMPSON, J BACTERIOL 171, 3583 (1989).

5. F. Flett, V. Mersinias, C. P. Smith, FEMS MICROBIOL LETT 155, 223 (1997).

6. 孙宁, 浙江大学 (2013).

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8. R. K. Holmes, M. G. Jobling, (1996-01-19, 1996).

9. J. A. HEINEMANN, G. F. SPRAGUE, NATURE 340, 205 (1989).

10. T. Kunik et al., P NATL ACAD SCI USA 98, 1871 (2001).

11. V. L. Waters, NAT GENET 29, 375 (2001).

12. E. Duchaud et al., NAT BIOTECHNOL 21, 1307 (2003).

13. M. Li, L. H. Qiu, Y. Pang, ANN MICROBIOL 57, 313 (2007).

14. C. Gatsogiannis et al., NATURE 495, 520 (2013-03-20, 2013).

15. R. Zhao et al., APPL ENVIRON MICROB 74, 7219 (2008-12-01, 2008).

16. M. Li et al., MOL BIOL REP 36, 785 (2009).

17. M. S. Kelker et al., PLOS ONE 9, (2014).

18. J. Sha, E. V. Kozlova, A. K. Chopra, INFECT IMMUN 70, 1924 (2002).



Toxin manufacture





termit