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| | <div class="side col-lg-3"> | | <div class="side col-lg-3"> |
| − | <nav class="dr-menu">
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| − | <h3 class="ml-5">Improvement</h3>
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| − | <ul>
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| − | <li><a class="fa fa-plug" href="#part-improvement"> Part Improvement</a>
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| − | <ul>
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| − | <li><a class="fa fa-plug" href="#introduction"> 1. Introduction</a></li>
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| − | <li><a class="fa fa-plug" href="#construction"> 2. Construction</a></li>
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| − | <li><a class="fa fa-plug" href="#measurement"> 3. Measurement</a>
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| − | <ul>
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| − | <li><a class="fa fa-plug" href="#RT-qPCR"> 3.1 RT-qPCR</a></li>
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| − | <li><a class="fa fa-plug" href="#characterization"> 3.2 Characterization</a>
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| − | <ul>
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| − | <li><a class="fa fa-plug" href="#growth-curve"> 3.2.1 Growth
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| − | Cueve</a></li>
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| − | <li><a class="fa fa-plug" href="#tryptophan-production"> 3.2.2
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| − | Tryptophan<br>Production</a></li>
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| − | </ul>
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| − | </li>
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| − | </ul>
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| − | </li>
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| − | </ul>
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| − | </li>
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| − |
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| − | </ul>
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| − | </nav>
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| | </div> | | </div> |
| | <div class="page xjtuText col-lg-8 col-12 justify-content-center"> | | <div class="page xjtuText col-lg-8 col-12 justify-content-center"> |
| − | <div class="highlightBox"> | + | <div class="row"> |
| − | <p>AroG (3-deoxy-7-phosphoheptulonate synthase, <a | + | <div class="col-12"> |
| − | href="https://www.brenda-enzymes.org/enzyme.php?ecno=2.5.1.54">EC 2.5.1.54</a>,
| + | <p class="float-right nav mt-3">This site has been archieved and moved to<a |
| − | <a href="http://parts.igem.org/Part:BBa_K1060000">BBa_K1060000</a>), catalyzes the | + | href="https://2021.igem.org/Team:XJTU-China/Improve"> |
| − | following reaction:<br>
| + | /Team:XJTU-China/Improve </a>. Sorry for the inconvenience caused.</p> |
| − | phosphoenolpyruvate+D-erythrose 4-phosphate+H2O = 3-deoxy-D-arabino-hept-2-ulosonate
| + | |
| − | 7-phosphate +phosphate
| + | |
| − | </p>
| + | |
| − | <p>The reaction is a key branching point of the glycolysis and shikimate pathways. Expression of
| + | |
| − | aroG can lead to more substrate into the shikimate pathway, which can improve the yield of
| + | |
| − | downstream products as tryptophan, phenylalanine, tyrosine and benzazole <i>etc.</i></p>
| + | |
| − | <p>AroG-S211F, in which the serine at 211 was replaced by phenylalanine, has also been reported
| + | |
| − | to be able to increase the production of downstream product in shikimate pathway. However
| + | |
| − | the structural mechanism is unclear. And also it is not sure whether it can increase the
| + | |
| − | production of our tryptophan. So In our project, aroG-S211F was overexpressed, attempted to
| + | |
| − | improve the production of tryptophan. </p>
| + | |
| − | <p>An inducible circuit BBa_K3832008 containing lacUV5-controlled aroG S211F were constructed to
| + | |
| − | characterize and measure the function of AroG-S211F in E.coli DH5alpha(Fig. 1.1). Firstly
| + | |
| − | the yield of tryptophan of mutant aroG and the native one respectively were detected by PDAB
| + | |
| − | method modified by ourselves. Secondly, considering that the over-expression of aroG will
| + | |
| − | significantly reduce the amount of substrate (glucose) entering the glycolysis pathway, in
| + | |
| − | turn affecting the normal cell proliferation, the effect of aroG-S211F on the cell
| + | |
| − | proliferation was also tested by the comparison of growth rate of the wild-type E.coli and
| + | |
| − | the engineered E.coli with aroG-S211F.</p>
| + | |
| − | </div>
| + | |
| − | <h2>1. Construction and Verification of aroG circuit</h2>
| + | |
| − | <p>aroG S211F gene was chemically synthetized by Genewiz and cloned into pET28a+ backbone by Golden
| + | |
| − | Gate assembly (BsaI). After transformed into E.coli DH5alpha, plasmid extraction and
| + | |
| − | electrophoresis, PCR amplification
| + | |
| − | and sequencing were conducted to confirm its correctness. The results are list in Fig. 1.1 </p>
| + | |
| − | <div class="imgWrapper centerize">
| + | |
| − | <img src="https://static.igem.org/mediawiki/2021/c/c3/T--XJTU-China--aroG.png" alt="Fig. 1.1">
| + | |
| − | <span class="description"><strong>Fig. 1.1 The DNA agarose gel electrophoresis result of
| + | |
| − | AroG-S211F circuit, plasmid and PCR product. </strong>(a) The length of the circuit is
| + | |
| − | 2503bp (b) The length of the plasmid is 4738bp. And the two discrete bands are thought as
| + | |
| − | either open-coiled or super-coiled plasmids (c)The amplicon is expected to be 2526bp.
| + | |
| − | </span>
| + | |
| − | </div>
| + | |
| − | <p>Meanwhile, the quantitatively assay by RT-qPCR was also performed to verified its mRNA level. As
| + | |
| − | shown in Fig. 2.2, the transcriptional level was increased about two folds after IPTG induction,
| + | |
| − | indicating the circuit was successfully constructed with functional aroG mutant. The basal
| + | |
| − | expression of aroG without IPTG induction can be observed due to one copy of native aroG in
| + | |
| − | E.coli genome.</p>
| + | |
| − | <div class="imgWrapper centerize">
| + | |
| − | <img src="https://static.igem.org/mediawiki/2021/2/21/T--XJTU-China--improvement3.1.png"
| + | |
| − | alt="Fig. 1.2">
| + | |
| − | <span class="description"><strong>Fig.3.1 The relative mRNA level of aroG-S211F in DH5alpha
| + | |
| − | strain with Part:BBa_K3832008 inserted in pET28a+ vector.</strong></span>
| + | |
| − | </div>
| + | |
| − | <h2>2. Characterization the effect of AroG-S211F on tryptophan production</h2>
| + | |
| − | <h3>2.1 Tryptophan can be easily determined by modified PDAB chromogenic method</h3>
| + | |
| − | <div class="card card-dark ml-5 mt-5 mb-5" style="width: 90%;">
| + | |
| − | <button class="btn btn-default" type="button" data-toggle="collapse"
| + | |
| − | data-target="#ncharacterization" aria-expanded="false" aria-controls="part">
| + | |
| − | Modified PDAB chromogenic Method
| + | |
| − | </button>
| + | |
| − | <div class="collapse" id="ncharacterization">
| + | |
| − | <div class="card card-body card-dark">
| + | |
| − | <ol style="color: white; font-family: 'eras';">
| + | |
| − | <li>Freeze-thaw bacterial culture medium with suspension cells for over 3 times.
| + | |
| − | </li>
| + | |
| − | <li>Add 100 ul medium into 400 ul PDAB (p-dimethylaminobezaldehyde) solution (3
| + | |
| − | mg/ml in
| + | |
| − | 9 M solution of sulfuric acid). Then keep at 60℃ for 20 min.</li>
| + | |
| − | <li>Add 3 ul 0.5% (w/w) solution of sodium nitrite. Then keep at 60℃ for
| + | |
| − | 15min.
| + | |
| − | </li>
| + | |
| − | <li>Measure absorption under 590 nm wavelength (OD<span class="sub">590</span>).
| + | |
| − | </li>
| + | |
| − | </ol>
| + | |
| − | </div>
| + | |
| | </div> | | </div> |
| | </div> | | </div> |
| − | <h3>2.2 The yield of tryptophan was significantly improved in AroG-S211F strain compared to native
| |
| − | AroG</h3>
| |
| − | <p>As shown in Fig. 2.1, compared with the E.coli harboring the blank vector and native aroG gene
| |
| − | (BBa_K1060000), the yield of tryptophan in the engineered E.coli with aroG-S211F induced by 1 mM
| |
| − | IPTG continuously increased in the 30 h cultivation (green triangle), reaching a maximal
| |
| − | productivity of 160 mg/ml per OD, while the blank controls slowly increased and maintained its
| |
| − | production at about 1200 min, arriving about 80 mg/ml per OD, half of the previous one (circle
| |
| − | and square). It is the same case in absent of IPTG (blue triangle), indicating the low leaky
| |
| − | expression of our circuit. In all, our circuit containing AroG-S211F can efficiently produce
| |
| − | tryptophan with the highest productivity of 160 mg/ml per OD, which can be further improved
| |
| − | under the control of toggle-switch. </p>
| |
| − | <div class="imgWrapper centerize">
| |
| − | <img src="https://static.igem.org/mediawiki/2021/2/2c/T--XJTU-China--improvement3.3.png"
| |
| − | alt="Fig. 2.1">
| |
| − | <span class="description"><strong>Fig. 2.1 The tryptophan production curve of the engineering
| |
| − | E.coli with aroG-S211F and E.coli with native aroG.</strong></span>
| |
| − | </div>
| |
| − |
| |
| − | <h3>2.3 The structural mechanisms was elucidated by protein structure modeling</h3>
| |
| − | <p>To explain the concrete mechanisms of the promotion effect by AroG-S211F comparing wild-type
| |
| − | AroG, protein structure modeling is used to analyze the thermodynamics and structure of them.
| |
| − | </p>
| |
| − | <p>From an energy perspective, our modeling results show that the mutant protein exhibits lower
| |
| − | binding free energy with the catalytic substrate in the presence of the inhibitor (Phe), that
| |
| − | is, it is able to bind more tightly and stably to the substrate, thus improving catalytic
| |
| − | efficiency. On the other hand, structural analysis also reflected that the binding tightness
| |
| − | between the mutated site and the inhibitor was reduced, which weakened its inhibitory effect.
| |
| − | </p>
| |
| − | <p>By the modeling result, the mutation (S211 to F211) in AroG is proposed to eliminate the
| |
| − | allosteric inhibition of phenylalanine, thus increasing the catalytic rate and downstream
| |
| − | product yield.</p>
| |
| − | <h2>4. Characterization the effect of aroG-S211F on cell proliferation</h2>
| |
| − | <p>The over-expression of aroG inhibits the glycolysis pathway, thus definitely affecting the cell
| |
| − | growth. So the effect of aroG-S211F on cell proliferation was also detected. The OD600 of
| |
| − | engineered E.coli and blank strain were continuously monitored, as shown in Fig. The Logistic
| |
| − | equation was used to fit the growth curve, the obvious inhibitory effect of aroG expression on
| |
| − | cell proliferation was observed, especially with IPTG induction. The growth parameters K
| |
| − | (environmental capacity) and r (intrinsic growth rate) of different experimental groups was also
| |
| − | obtained from the fitting Logistic curve, and the parameter r decreased dramatically in E.coli
| |
| − | with aroG-S211F induced by IPTG, indicating the increased doubling time of the cell. </p>
| |
| − | <div class="imgWrapper centerize">
| |
| − | <img src="https://static.igem.org/mediawiki/2021/f/f2/T--XJTU-China--POC-Fig2-3.png" alt="Fig. 4.1">
| |
| − | <span class="description"><strong>Fig. 3.2</strong> (a) The population density of E.coli was
| |
| − | measured at 600nm by
| |
| − | colorimetry. The scatter represents the result of the measurement. The Logistic equation was
| |
| − | used to fit the growth curve, and the fitting results were shown in the curve. (b) shows the
| |
| − | growth parameters K (environmental capacity) and r (intrinsic growth rate) of different
| |
| − | experimental groups obtained from the fitting results in (a).</span>
| |
| − | </div>
| |
| − | <h2>5. Conclusions:</h2>
| |
| − | <p>A lacUV5 controlled-aroG S211F gene circuit was successfully constructed, and the overexpression
| |
| − | of aroG-S211F significantly improved the tryptophan production, with a highest productivity of
| |
| − | 160 mg/ml per OD. Protein structure modeling elucidate that the improvement may attribute to the
| |
| − | elimination of the allosteric inhibition of phenylalanine, thus increasing the catalytic rate
| |
| − | and downstream product yield. However, because of the inhibition on the glycolysis pathway of
| |
| − | aroG, the cell growth was obviously inhibited. The results confirmed our hypothesis that cell
| |
| − | proliferation and tryptophan production should be separated, and it has been designed to be
| |
| − | strictly controlled by toggle-switch circuit, in which cell proliferation (pykA gene
| |
| − | overexpression) and tryptophan production (aroG-S211F overexpression) was constructed in the two
| |
| − | arms of toggle-switch. (View our design on Team:XJTU-China/Design).</p>
| |
| | </div> | | </div> |
| − | <!-- <div class="page xjtuText col-lg-8 col-12 justify-content-center">
| |
| − | <a class="anchor" id="part-improvement"></a>
| |
| − | <h1 class="ml-3">Part improvement</h1>
| |
| − | <a class="anchor" id="introduction"></a>
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| − | <h2 class="ml-5">1. Introduction</h2>
| |
| − | <p>AroG (3-deoxy-7-phosphoheptulonate synthase, EC 2.5.1.54) is a key enzyme in the metabolism of
| |
| − | aromatic amino acids, catalysis following reaction:<br>
| |
| − | phosphoenolpyruvate + D-erythrose-4-phosphate+H2O =
| |
| − | 3-deoxy-D-arabino-hept-2-ulosonate-7-phosphate +phosphate</p>
| |
| − | <p>Wild aroG functions in the form of tetramer, which can be inhibited by its allosteric inhibitors
| |
| − | Phenylalanine (Phe). In order to increase the production of downstream products such as
| |
| − | tryptophan, Ser on site 211 of aroG was mutated to Phe to remove the inhibitory effect of Phe.
| |
| − | The CDS of the mutant (aroG-S211F, Part:BBa_3832000) is our improvement version of
| |
| − | Part:BBa_K1060000 which encodes wild-type aroG.</p>
| |
| − | <p>We used protein structure prediction tool (Alphafold2) to predict the structure of the mutant
| |
| − | aroG-S211F, and compared its ability to bind to substrates in the presence of Phe with that of
| |
| − | the wild type. </p>
| |
| − | <p>In our project, aroG-S211F is used to improve the production of tryptophan. Considering the
| |
| − | over-expression of aroG-S211F could significantly reduce the amount of substrate (glucose)
| |
| − | entering the glycolysis reaction, in turn affects the normal process of cell proliferation, the
| |
| − | expression of aroG is designed under strict control by toggle-switch circuit.</p>
| |
| − | <a class="anchor" id="construction"></a>
| |
| − | <h2 class="ml-5">2. Construction</h2>
| |
| − | <p>An inducible circuit (Part:BBa_K3832008) is constructed to characterize and measure the function
| |
| − | of aroG-S211F (Fig.2.1). LacUV5 promoter is used while LacI is also contained in our circuit as
| |
| − | a repressor. </p>
| |
| − | <div class="imgWrapper centerize">
| |
| − | <img src="https://static.igem.org/mediawiki/2021/f/fe/T--XJTU-China--POC-Fig2-1.png"
| |
| − | alt="Design of the inducible circuit for aroG-S211F" width="60%">
| |
| − | <span class="description"><strong>Fig. 2.1 Design of the inducible circuit for
| |
| − | aroG-S211F</strong></span>
| |
| − | </div>
| |
| − | <p>Both GolgenGate assembly and In-Fusion assembly are used to construct the circuit from basic
| |
| − | parts and insert into pET28a+ vector (In-Fusion assembly is done with the help of partner team
| |
| − | NWU-CHINA-A as our collaboration). </p>
| |
| − | <div class="card card-dark ml-5 mt-5 mb-5" style="width: 90%;">
| |
| − | <button class="btn btn-default" type="button" data-toggle="collapse" data-target="#GG"
| |
| − | aria-expanded="false" aria-controls="part">
| |
| − | Method (for Golden Gate Assembly)
| |
| − | </button>
| |
| − | <div class="collapse" id="GG">
| |
| − | <div class="card card-body card-dark">
| |
| − | <p>
| |
| − | <b>Reaction:</b><br>
| |
| − | Insert (purified PCR product)/ng= Length/bp × 1.08×102
| |
| − | Vector (purified PCR product)/ng= Length/bp × 2.16×102
| |
| − | BsaI-HFv2 (20U/ul) = 1 ul
| |
| − | T4 ligase (1000U/ul) = 1 ul
| |
| − | T4 ligase buffer (10×) = 2 ul
| |
| − | ddH20 = 20 ul
| |
| − | </p>
| |
| − | <p><b>Condition:</b></p>
| |
| − | <table class="ml-5 table table-striped table-light" style="width: 90%;">
| |
| − | <thead>
| |
| − | <tr>
| |
| − | <th scope="col">Temperature</th>
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| − | <th scope="col">Time</th>
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| − | <th scope="col">Cycle</th>
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| − | </tr>
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| − | </thead>
| |
| − | <tbody>
| |
| − | <tr>
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| − | <th scope="row">37 ℃</th>
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| − | <td>15 min</td>
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| − | <td rowspan="2">10</td>
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| − | </tr>
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| − | <tr>
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| − | <th scope="row">16 ℃</th>
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| − | <td>10 min</td>
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| − | </tr>
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| − | <tr>
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| − | <th scope="row">37 ℃</th>
| |
| − | <td>10 min</td>
| |
| − | <td>1</td>
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| − | </tr>
| |
| − | <tr>
| |
| − | <th scope="row">65 ℃</th>
| |
| − | <td>10 min</td>
| |
| − | <td>1</td>
| |
| − | </tr>
| |
| − | <tr>
| |
| − | <th scope="row">80 ℃</th>
| |
| − | <td>10 min</td>
| |
| − | <td>1</td>
| |
| − | </tr>
| |
| − | <tr>
| |
| − | <th scope="row" colspan="3">Store at 4 ℃</th>
| |
| − | </tr>
| |
| − | </tbody>
| |
| − | </table>
| |
| − | <p><b>Transformation: </b><br>
| |
| − | Using Trelief<span class="sub">TM</span> 5α Chemically Competent Cell (Tsingke
| |
| − | Biotechnology Co., Ltd.)
| |
| − | Add 20 ul assembly product in 50 ul competent cell, ice bath for 30 min.
| |
| − | Heat shock 42℃ for 45 sec.
| |
| − | Ice bath for 2 min.
| |
| − | Recover in 1ml SOC medium, 37℃, 200rpm, for 1 hour.
| |
| − | Spread to LB plate with 50 ug/ml kanamycin, 37℃ for 10-16 hours.
| |
| − | </p>
| |
| − | </div>
| |
| − | </div>
| |
| − | </div>
| |
| − | <div class="imgWrapper centerize">
| |
| − | <img src="https://static.igem.org/mediawiki/2021/c/c3/T--XJTU-China--aroG.png" alt="AroG-S211F gel">
| |
| − | <span class="description"><strong>Fig. 2.2 The DNA agarose gel electrophoresis result of
| |
| − | AroG-S211F circuit, plasmid and PCR product. </strong>(a) The length of the circuit is
| |
| − | 2503bp (b) The length of the plasmid is 4738bp. And the two discrete bands are thought as
| |
| − | either open-coiled or super-coiled plasmids (c)The amplicon is expected to be 2526bp.
| |
| − | </span>
| |
| − | </div>
| |
| − | <p>The constructed plasmid of AroG-S211F are then subjected to PCR amplification to verify the
| |
| − | length of circuit, and the expected amplicon is 2526bp in length. Fig.2.2 shows the fragment of
| |
| − | the inducible circuit (panel a),
| |
| − | corresponding cloned vector (panel b) and the amplicon (panel c). The result suggests plasmid
| |
| − | obtained contains an insert with proper length identical to the circuit, thus indicating the
| |
| − | plasmid to be successfully constructed. The sequencing result (unpublished) also conforms to
| |
| − | this suggestion.</p>
| |
| − | <a class="anchor" id="measurement"></a>
| |
| − | <h2 class="ml-5">3. Measurement</h2>
| |
| − | <a class="anchor" id="RT-qPCR"></a>
| |
| − | <h3 class="ml-5">3.1 RT-qPCR</h3>
| |
| − | <p>RT-qPCR is used to detect the transcription of aroG-S211F as first step.</p>
| |
| − | <div class="card card-dark ml-5 mt-5 mb-5" style="width: 90%;">
| |
| − | <button class="btn btn-default" type="button" data-toggle="collapse" data-target="#RT"
| |
| − | aria-expanded="false" aria-controls="part">
| |
| − | Method
| |
| − | </button>
| |
| − | <div class="collapse" id="RT">
| |
| − | <div class="card card-body card-dark">
| |
| − | <p><b>Cultivation:</b> Using LB liquid medium, 37℃, 200rpm. <br>
| |
| − | <b>Inducing condition:</b> 1 mM IPTG, over 8 hours.<br>
| |
| − | <b>Total RNA extraction:</b> Using RNAsimple Total RNA Kit,DP419 (TIANGEN BIOTECH
| |
| − | (BEIJING) CO.,LTD.)<br>
| |
| − | <b>cDNA preparation:</b> Using Evo M-MLV RT Mix (Vazyme Biotech Co.,Ltd); template
| |
| − | concentration: 50ng RNA/ul; reaction condition: 37℃ 15min, 85℃
| |
| − | 15sec.<br>
| |
| − | <b>qPCR:</b> Using ChamQ SYBR qPCR Master Mix (Vazyme Biotech Co.,Ltd).<br>
| |
| − |
| |
| − | Relative Normalized Expression data is calculated by using the equation below,<br>
| |
| − | Relative Expression = 2<span class="sup">-[ΔC<span class="sub">t</span>(T)-ΔC<span
| |
| − | class="sub">t</span>(C)]</span><br>
| |
| − | where ΔC<span class="sub">t</span>(T) represents the difference between C<span
| |
| − | class="sub">t</span> value of target gene and internal
| |
| − | standard gene in treatment group; ΔC<span class="sub">t</span>(C) represents the
| |
| − | difference between C<span class="sub">t</span> value
| |
| − | of target gene and internal standard gene in negative control group.
| |
| − | </p>
| |
| − | </div>
| |
| − | </div>
| |
| − | </div>
| |
| − | <p><b>Result:</b><br> As in Fig.3.1, expression of aroG-S211F under induction by IPTG is higher than
| |
| − | that in un-induced
| |
| − | group and negative control (DH5alpha with blank pET28a+ vector).</p>
| |
| − | <div class="imgWrapper ceterize">
| |
| − | <img src="https://static.igem.org/mediawiki/2021/2/21/T--XJTU-China--improvement3.1.png" alt="RTaroG"
| |
| − | width="60%">
| |
| − | <span class="description"><strong>Fig.3.1 The relative mRNA level of aroG-S211F in DH5alpha
| |
| − | strain with
| |
| − | Part:BBa_K3832008 inserted in pET28a+ vector.</strong></span>
| |
| − | </div>
| |
| − | <a class="anchor" id="characterization"></a>
| |
| − | <h3 class="ml-5">3.2 Characterization</h3>
| |
| − | <a class="anchor" id="growth-curve"></a>
| |
| − | <h4 class="ml-5">3.2.1 Growth Curve</h4>
| |
| − | <p>As is showed in Fig.3.2, by using the Logistic equation to fit the growth curve, the inhibitory
| |
| − | effect of aroG expression on cell proliferation was verified (as the parameter r decreased in
| |
| − | <i>E.coli</i> with aroG-S211F and induced by IPTG, which represents the reciprocal of the time
| |
| − | it takes
| |
| − | for the population to double). <br>
| |
| − | Cultivation condition: 20 ml LB medium, 37℃, 200rpm; Inoculation dose: 20 ul (0.1%)
| |
| − | </p>
| |
| − | <div class="imgWrapper ceterize">
| |
| − | <img src="https://static.igem.org/mediawiki/2021/f/f2/T--XJTU-China--POC-Fig2-3.png" alt="Fig. 3.2"
| |
| − | width="60%">
| |
| − | <span class="description"><strong>Fig. 3.2</strong> (a) The population density of <i>E.coli</i>
| |
| − | was
| |
| − | measured at 600 nm
| |
| − | by colorimetry. The scatter represents the result of the measurement. The Logistic equation
| |
| − | was used to fit the growth curve, and the fitting results were shown in the curve. (b) and
| |
| − | (c) respectively show the growth parameters K (environmental capacity) and r (intrinsic
| |
| − | growth rate) of different experimental groups obtained from the fitting results in
| |
| − | (a).</span>
| |
| − | </div>
| |
| − | <a class="anchor" id="tryptophan-production"></a>
| |
| − | <h4 class="ml-5">3.2.2 Tryptophan Production</h4>
| |
| − | <p>Fig. 3.3 shows the yield of tryptophan. The engineered <i>E.coli</i> with aroG-S211F induced by 1
| |
| − | mM
| |
| − | IPTG resents an increased production of tryptophan, comparing in absent of IPTG or aroG-S211F
| |
| − | (within blank pET28a+ vector).</p>
| |
| − | <p>Concentration of tryptophan is calculated by standard curve in Fig.3.4. Tryptophan production is
| |
| − | calculated by removing the concentration of blank medium, and normalized by divided by OD<span
| |
| − | class="sub">600</span>
| |
| − | (reflecting cell density).</p>
| |
| − | <div class="imgWrapper ceterize">
| |
| − | <img src="https://static.igem.org/mediawiki/2021/2/2c/T--XJTU-China--improvement3.3.png"
| |
| − | alt="Fig 3.3" width="60%">
| |
| − | <span class="description"><strong>Fig. 3.3 The relationship between tryptophan concentration in
| |
| − | culture
| |
| − | medium and culture time.</strong> The concentration of tryptophan is measured by PDAB
| |
| − | chromogenic
| |
| − | method. </span>
| |
| − | </div>
| |
| − | <div class="card card-dark ml-5 mt-5 mb-5" style="width: 90%;">
| |
| − | <button class="btn btn-default" type="button" data-toggle="collapse"
| |
| − | data-target="#ncharacterization" aria-expanded="false" aria-controls="part">
| |
| − | Method
| |
| − | </button>
| |
| − | <div class="collapse" id="ncharacterization">
| |
| − | <div class="card card-body card-dark">
| |
| − | <ol style="color: white; font-family: 'eras';">
| |
| − | <li>Freeze-thaw bacterial culture medium with suspension cells for over 3 times.
| |
| − | </li>
| |
| − | <li>Add 100 ul medium into 400 ul PDAB (p-dimethylaminobezaldehyde) solution (3
| |
| − | mg/ml in
| |
| − | 9 M solution of sulfuric acid). Then keep at 60℃ for 20 min.</li>
| |
| − | <li>Add 3 ul 0.5% (w/w) solution of sodium nitrite. Then keep at 60℃ for
| |
| − | 15min.
| |
| − | </li>
| |
| − | <li>Measure absorption under 590 nm wavelength (OD<span class="sub">590</span>).
| |
| − | </li>
| |
| − | </ol>
| |
| − | </div>
| |
| − | </div>
| |
| − | </div>
| |
| − | <p>The same method should be used to determine the OD<span class="sub">590</span> of a tryptophan
| |
| − | standard solution at a
| |
| − | known concentration to obtain a standard curve. Standard curve measured and used in our
| |
| − | experiment is as Fig.3.4.</p>
| |
| − | <div class="imgWrapper ceterize">
| |
| − | <img src="https://static.igem.org/mediawiki/2021/a/ab/T--XJTU-China--improvement3.4.png"
| |
| − | alt="Fig 3.4" width="60%">
| |
| − | <span class="description"><strong>Fig.3.4 Standard curve of measuring tryptophan tryptophan by
| |
| − | PDAB method.</strong></span>
| |
| − | </div>
| |
| − | </div> -->
| |
| | <div class="col-lg-1"></div> | | <div class="col-lg-1"></div> |
| | </div> | | </div> |
