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− | <i class="liticon wow bounceInLeft flaticon-bacteria"></i> <h4 class="header4 displayControl">Glycerol stocks preparation and Sample Growth </h4> | + | <i class="liticon wow bounceInLeft delay02 flaticon-bacteria"></i> <h4 class="header4 displayControl">Glycerol stocks preparation and Sample Growth </h4> |
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| <p>A single colony was inoculated with a sterile pipette tip in a test tube with <span class="i_enph quantity">10 ml</span> of LB and antibiotic (1000:1 LB to antibiotic ratio) and placed in the thermoshaker (<span class="i_enph quantity">190 rpm</span>, <span class="i_enph quantity">37°C</span>. When the culture got cloudy</span>, <span class="i_enph quantity">40 ml</span> of LB+antibiotic were added to reach a final volume of <span class="i_enph quantity">50 ml</span>. The cells were grown until an OD600 of <span class="i_enph quantity">0.5</span> and then centrifuged at <span class="i_enph quantity">4100 rpm</span> for <span class="i_enph quantity">10 minutes</span> at <span class="i_enph quantity">4 °C</span>. The supernatant was discarded and the cells were resuspend in <span class="i_enph quantity">5 ml</span> of LB + antibiotic + glycerol (<span class="i_enph quantity">20% v/v</span>). The cells were kept on ice and were promptly aliquoted into <span class="i_enph quantity">200 μl</span> tubes and frozen at <span class="i_enph quantity">-80°C</span> immediately. From this protocol we obtained a <span class="i_enph quantity">10X</span> concentrated glycerol stock for each sample.</p> | | <p>A single colony was inoculated with a sterile pipette tip in a test tube with <span class="i_enph quantity">10 ml</span> of LB and antibiotic (1000:1 LB to antibiotic ratio) and placed in the thermoshaker (<span class="i_enph quantity">190 rpm</span>, <span class="i_enph quantity">37°C</span>. When the culture got cloudy</span>, <span class="i_enph quantity">40 ml</span> of LB+antibiotic were added to reach a final volume of <span class="i_enph quantity">50 ml</span>. The cells were grown until an OD600 of <span class="i_enph quantity">0.5</span> and then centrifuged at <span class="i_enph quantity">4100 rpm</span> for <span class="i_enph quantity">10 minutes</span> at <span class="i_enph quantity">4 °C</span>. The supernatant was discarded and the cells were resuspend in <span class="i_enph quantity">5 ml</span> of LB + antibiotic + glycerol (<span class="i_enph quantity">20% v/v</span>). The cells were kept on ice and were promptly aliquoted into <span class="i_enph quantity">200 μl</span> tubes and frozen at <span class="i_enph quantity">-80°C</span> immediately. From this protocol we obtained a <span class="i_enph quantity">10X</span> concentrated glycerol stock for each sample.</p> |
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− | <i class="liticon wow bounceInLeft flaticon-atom27"></i> <h4 class="header4 displayControl">Fluorescence readings: Tecan INFINITE ® 200 PRO Plate Reader </h4> | + | <i class="liticon wow bounceInLeft delay03 flaticon-atom27"></i> <h4 class="header4 displayControl">Fluorescence readings: Tecan INFINITE ® 200 PRO Plate Reader </h4> |
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− | <i class="liticon wow bounceInLeft flaticon-camera65"></i> <h4 class="header4 displayControl">Fluorescence readings: Cary Eclipse Fluorescence Spectrophotometer </h4> | + | <i class="liticon wow bounceInLeft delay05 flaticon-camera65"></i> <h4 class="header4 displayControl">Fluorescence readings: Cary Eclipse Fluorescence Spectrophotometer </h4> |
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− | <i class="liticon wow bounceInLeft flaticon-bars-graphic"></i> <h4 class="header4 displayControl">Fluorescence readings: BioRad CFX96 TouchTM Real-Time PCR Detection System</h4> | + | <i class="liticon wow bounceInLeft delay06 flaticon-bars-graphic"></i> <h4 class="header4 displayControl">Fluorescence readings: BioRad CFX96 TouchTM Real-Time PCR Detection System</h4> |
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− | <i class="liticon wow bounceInLeft flaticon-increasing5"></i> <h4 class="header4 displayControl">Fluorescence readings: BD FACSCanto</h4> | + | <i class="liticon wow bounceInLeft delay02 flaticon-increasing5"></i> <h4 class="header4 displayControl">Fluorescence readings: BD FACSCanto</h4> |
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− | <i class="liticon wow bounceInLeft flaticon-test17"></i> <h4 class="header4 displayControl">Fluorescence readings: E. coli S30 Extract System for DNA Circular </h4> | + | <i class="liticon wow bounceInLeft delay03 flaticon-test17"></i> <h4 class="header4 displayControl">Fluorescence readings: E. coli S30 Extract System for DNA Circular </h4> |
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| <p>Miniprepped DNA was purified and extracted through phenol/chloroform extraction followed by ethanol precipitation. Reactions were set following Promega E. coli S30Extract System Technical Bulletin and were performed using Qiagen Rotor-Gene Q (made in USA). Parameters for this specific experiment were set as follows:</p> | | <p>Miniprepped DNA was purified and extracted through phenol/chloroform extraction followed by ethanol precipitation. Reactions were set following Promega E. coli S30Extract System Technical Bulletin and were performed using Qiagen Rotor-Gene Q (made in USA). Parameters for this specific experiment were set as follows:</p> |
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− | <h4 class="header4-resume">Our characterization confirmed the relative strength of the promoters</h4> | + | <h4 class="header4-resume wow fadeInDown">Our characterization confirmed the relative strength of the promoters</h4> |
| <p><span class="i_enph">J23101/J23106</span> fluorescence ratios ranged from 2.0 to 4.5, depending on the strain and the technique. Differently from the other two promoters, <span class="i_enph">J23117</span> showed a very low GFP production, as it was not detectable by eye or using the trans-illuminator and showed little fluorescence with the three techniques used.</p> | | <p><span class="i_enph">J23101/J23106</span> fluorescence ratios ranged from 2.0 to 4.5, depending on the strain and the technique. Differently from the other two promoters, <span class="i_enph">J23117</span> showed a very low GFP production, as it was not detectable by eye or using the trans-illuminator and showed little fluorescence with the three techniques used.</p> |
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− | <h4 class="header4-resume">Ratios across promoters are kept the same</h4> | + | <h4 class="header4-resume wow fadeInDown">Ratios across promoters are kept the same</h4> |
| <p><span class="i_enph">J23101/J23106</span> fluorescence ratios ranged from 2.0 to 4.5, depending on the strain and the technique. Differently from the other two promoters, <span class="i_enph">J23117</span> showed a very low GFP production, as it was not detectable by eye or using the trans-illuminator and showed little fluorescence with the three techniques used.</p> | | <p><span class="i_enph">J23101/J23106</span> fluorescence ratios ranged from 2.0 to 4.5, depending on the strain and the technique. Differently from the other two promoters, <span class="i_enph">J23117</span> showed a very low GFP production, as it was not detectable by eye or using the trans-illuminator and showed little fluorescence with the three techniques used.</p> |
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− | <h4 class="header4-resume">Different techniques lead to the same results, with different sensitivities</h4> | + | <h4 class="header4-resume wow fadeInDown">Different techniques lead to the same results, with different sensitivities</h4> |
| <p>The best way to perform a characterization is to use various techniques. Throughout our experiments we saw that each instrument has a specific sensitivity, which alters the output data. The FACS happened to be the most accurate among all, due to its extremely high intrinsic sentivity. The plate reader also showed a good accuracy while the fluorimeter was not able to detect the weakest promoter from the background noise, due to its low intrinsic sensitivity.</p> | | <p>The best way to perform a characterization is to use various techniques. Throughout our experiments we saw that each instrument has a specific sensitivity, which alters the output data. The FACS happened to be the most accurate among all, due to its extremely high intrinsic sentivity. The plate reader also showed a good accuracy while the fluorimeter was not able to detect the weakest promoter from the background noise, due to its low intrinsic sensitivity.</p> |
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− | <h4 class="header4-resume">Bacterial strain does matter</h4> | + | <h4 class="header4-resume wow fadeInDown">Bacterial strain does matter</h4> |
| <p>The three promoters behaved differently in the different bacterial strains used. The bacterial strain which gave the highest fluorescence was NEB10Beta cells in all cases showed a significant increased expression of the protein, compared to JM109 and NEB Express. We hypothesized this discordance among strains is due to their different genotypes. A different bacterial proteome (i.e. presence/lack of specific proteases and/or chaperonins, polymerases efficiency) may alter protein production, processing and folding, thus fluorescence emission.</p> | | <p>The three promoters behaved differently in the different bacterial strains used. The bacterial strain which gave the highest fluorescence was NEB10Beta cells in all cases showed a significant increased expression of the protein, compared to JM109 and NEB Express. We hypothesized this discordance among strains is due to their different genotypes. A different bacterial proteome (i.e. presence/lack of specific proteases and/or chaperonins, polymerases efficiency) may alter protein production, processing and folding, thus fluorescence emission.</p> |
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− | <h4 class="header4-resume">In vitro conditions mimic the in vivo reality</h4> | + | <h4 class="header4-resume wow fadeInDown">In vitro conditions mimic the in vivo reality</h4> |
| <p>Characterization in vitro using techniques like the cell-free extract and the qPCR allows to quantify the promoter strength by measuring transcript level, rather than just looking at the protein production. This approach gives a better understanding on the promoter`s nature, since it`s well known that the central dogma in biology is not always respected.</p> | | <p>Characterization in vitro using techniques like the cell-free extract and the qPCR allows to quantify the promoter strength by measuring transcript level, rather than just looking at the protein production. This approach gives a better understanding on the promoter`s nature, since it`s well known that the central dogma in biology is not always respected.</p> |
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