Difference between revisions of "Part:BBa K4645014"
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<partinfo>BBa_K4645014 short</partinfo> | <partinfo>BBa_K4645014 short</partinfo> | ||
− | RelE is a toxin protein that inhibits translation. RNA thermosensors which could inhibit downstream gene expression when the temperature is 37 ℃ but not affect downstream gene expression significantly when the temperature is below 28 ℃.The combination of two components can regulate the expression of toxin proteins by changing the temperature, and then control the death of engineering bacteria. | + | RelE is a toxin protein that inhibits translation. RNA thermosensors which could inhibit downstream gene expression when the temperature is 37 ℃ but not affect downstream gene expression significantly when the temperature is below 28 ℃. The combination of two components can regulate the expression of toxin proteins by changing the temperature, and then control the death of engineering bacteria. |
The circuit is shown in the figure below. | The circuit is shown in the figure below. | ||
<html> | <html> | ||
Line 14: | Line 14: | ||
<center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/rnarele.png" style="width:50%; "></center> | <center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/rnarele.png" style="width:50%; "></center> | ||
<br> | <br> | ||
− | + | ||
</body> | </body> | ||
</html> | </html> | ||
+ | ==Basic Elements== | ||
+ | <p><b>RNA thermosensors:</b> This is one of heat-repressible RNA thermosensors which could inhibit downstream gene expression when the temperature is 37 ℃ but not affect downstream gene expression significantly when the temperature is below 26 ℃. | ||
+ | </p> | ||
+ | <p><b>RelE toxin:</b> The RelE toxin is an RNase that preferentially cleaves mRNAs bound to the ribosome at the second position of stop codons. </p> | ||
+ | ==Basic Elements Functional validation == | ||
+ | ===RNA thermosensors=== | ||
+ | <b>To validate the function of the RNA thermosensor, we used two methods to experimentally verify it.</b> | ||
+ | ====Test Design (Method 1)==== | ||
+ | First we placed the AmCyan protein after the RNA thermosensor in the PUC57 plasmid and expressed the plasmid in <i>E. coli</i> DH5α. After culturing for 4 hours continuously at 36℃, 26℃ and 16℃ respectively, the fluorescence intensity was detected and divided by the OD<sub>600</sub> value, with DH5α cultured at 36℃ for 4 hours without plasmid transformation as control. The relative fluorescence intensity was detected to verify the function of the RNA thermosensor. | ||
+ | <html> | ||
+ | <head> | ||
+ | <meta charset="utf-8"> | ||
+ | <title>无标题文档</title> | ||
+ | </head> | ||
+ | <body> | ||
+ | <center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/rnaamcyan.jpg" style="width:50%; "></center> | ||
+ | <br> | ||
+ | </body> | ||
+ | </html> | ||
− | ===Test | + | ====Test Protocol (Method 1)==== |
− | + | <p> 1) Methods of molecular cloning and transformation are described above. Transform this plasmid into <i>E. coli</i> DH5α. Then spread it onto LB medium plates with 170 μg/mL chloramphenicol and incubate overnight at 37 ℃ in an incubator. </p> | |
+ | <p> 2) Pick four colonies from the same plate as parallel repeats. Each colony is inoculated in two identical media with 5 ml LB medium containing 170 μg/mL chloramphenicol and cultured at temperature (36 ℃) respectively while shaking at 200 rpm.</p> | ||
+ | <p> 3) Measure the OD<sub>600</sub> value of the resuspension culture media in an automatic microplate reader (<b>Synergy</b><sup>TM</sup> H1 hybrid multimodal reader) until the OD<sub>600</sub> of the bacteria solution reaches 0.4-0.6. </p> | ||
+ | <p> 4) After grouping the samples, culture them continuously for 4 hours at 36℃, 26℃ and 16℃ respectively while shaking at 200 rpm.</p> | ||
+ | <p> 5) Continuously measure fluorescence intensity (Exλ:453nm Emλ:486nm) and OD<sub>600</sub> using an automatic microplate reader (<b>Synergy</b><sup>TM</sup> H1 hybrid multimodal reader). After detection, divide the measured fluorescence intensity by OD<sub>600</sub> to obtain the relative fluorescence intensity and analyze the results.</p> | ||
− | ===Test Protocol(Method 1)=== | + | ====Result(Method 1)==== |
− | <b>Toxin protein RelE | + | <html> |
− | <p> 1) Methods of molecular cloning and transformation are described above. Transform this plasmid into E. coli BL21. Then spread it onto LB medium plates with 50 μg/mL kanamycin and incubate overnight at | + | <head> |
− | <p> 2) Pick four colonies from the same plate as parallel repeats. Each colony is inoculated in two identical media with 5 ml LB medium containing 50 μg/mL kanamycin and cultured at temperature ( | + | <meta charset="utf-8"> |
− | <p> 3) Measure the | + | <title>无标题文档</title> |
+ | </head> | ||
+ | <body> | ||
+ | <center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/rna2-1.jpg" style="width:60%; "></center> | ||
+ | <br> | ||
+ | <center><b>Figure 1. Analysis of Differential Relative Fluorescence Intensity under Four Hours of Different Temperature Induction Conditions </b> </center> | ||
+ | <br> | ||
+ | </body> | ||
+ | </html> | ||
+ | |||
+ | ====Test Design (Method 2)==== | ||
+ | We referred to the verification method of<b> iGEM21_HZAU-China BBa_K3733043</b> to verify the RNA thermosensor. We connected the toxin protein HepT after the RNA thermosensor and expressed it in <i>E. coli</i> DH5α using a plasmid. | ||
+ | <html> | ||
+ | <head> | ||
+ | <meta charset="utf-8"> | ||
+ | <title>无标题文档</title> | ||
+ | </head> | ||
+ | <body> | ||
+ | <center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/rnahept.jpg" style="width:45%; "></center> | ||
+ | <br> | ||
+ | </body> | ||
+ | </html> | ||
+ | |||
+ | ====Test Protocol (Method 2)==== | ||
+ | <p> 1) Methods of molecular cloning and transformation are described above. Transform this plasmid into <i>E. coli</i> DH5α. Then spread it onto LB medium plates with 170 μg/mL chloramphenicol and incubate overnight at 37 °C in an incubator.</p> | ||
+ | <p> 2) Pick four colonies from the same plate as parallel repeats. Each colony is inoculated in two identical media with 5 ml LB medium containing 170 μg/mL chloramphenicol and cultured at temperature (37℃) respectively while shaking at 200 rpm overnight.</p> | ||
+ | <p> 3) Measure the OD<sub>600</sub> value of the resuspending culture media in an automatic microplate reader (<b>Synergy</b><sup>TM</sup> H1 hybrid multimodal reader) until the OD<sub>600</sub> of the bacteria solution reaches 0.4-0.6. </p> | ||
+ | <p> 4) After grouping the samples, culture them continuously for 4 hours at 36℃ and 26℃ respectively, while shaking at 200 rpm.</p> | ||
+ | <p> 5) Continuously measure fluorescence intensity (Exλ:453nm Emλ:486nm) and OD<sub>600</sub> using an automatic microplate reader (<b>Synergy</b><sup>TM</sup> H1 hybrid multimodal reader). After detection, divide the measured fluorescence intensity by OD<sub>600</sub> to obtain the relative fluorescence intensity and analyze the results.</p> | ||
+ | |||
+ | ====Result(Method 2)==== | ||
+ | <html> | ||
+ | <head> | ||
+ | <meta charset="utf-8"> | ||
+ | <title>无标题文档</title> | ||
+ | </head> | ||
+ | <body> | ||
+ | <center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/rna2-2.jpg" style="width:60%; "></center> | ||
+ | <br> | ||
+ | <center><b>Figure 2. Bacterial OD<sub>600</sub> over time </b></center> | ||
+ | <br> | ||
+ | <center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/img-20231007-1520221.jpg" style="width:50%; "></center> | ||
+ | <br> | ||
+ | <center><b>Figure 3. Phenotypic result comparison chart </b></center> | ||
+ | <br> | ||
+ | </body> | ||
+ | </html> | ||
+ | |||
+ | ====Analysis of the experimental results==== | ||
+ | Results and analysis: | ||
+ | Both verification methods successfully validated that the RNA thermosensor can function and express proteins at 26℃ or lower temperatures. However, the experimental results also showed that there was some leakage from the RNA thermosensor at 36℃, which may lead to some adverse effects. | ||
+ | |||
+ | ====Model==== | ||
+ | In order to gain a clearer understanding and validate the feasibility of the RNA thermosensor, we used DINAMelt's server for analysis of the neck ring structure.In the experiment, we obtained the fluorescence intensity of three points and assigned high weights to the experimental values, which in turn transformed into the probability of opening the loop. We have obtained the following graph <b>Figure 4</b>, which, although different from the open-loop probability graph we recognize, does indeed match the results of our experiment. | ||
+ | <html> | ||
+ | <head> | ||
+ | <meta charset="utf-8"> | ||
+ | <title>无标题文档</title> | ||
+ | </head> | ||
+ | <body> | ||
+ | <center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/image.png" style="width:50%; "></center> | ||
+ | <br> | ||
+ | <center><b>Figure 4. RNA thermosensor open-loop probability chart. </b></center> | ||
+ | </body> | ||
+ | </html> | ||
+ | |||
+ | ===RelE toxin=== | ||
+ | <b>To validate the function of the RelE toxin, we used two methods to experimentally verify it.</b> | ||
+ | ====Test Design==== | ||
+ | In our experiment, we constructed a plasmid vector with RelE toxin protein connected after the lactose promoter and introduced it into <i>E. coli</i> BL21(DE3). IPTG was used to induce expression and OD<sub>600</sub> was detected continuously for 4 hours. Samples were taken every 30 minutes, diluted and plated to determine viable cell counts. | ||
+ | |||
+ | ====Test Protocol==== | ||
+ | <b>Toxin protein RelE OD<sub>600</sub> detection</b> | ||
+ | <p> 1) Methods of molecular cloning and transformation are described above. Transform this plasmid into <i>E. coli</i> BL21. Then spread it onto LB medium plates with 50 μg/mL kanamycin and incubate overnight at 37℃ in an incubator. </p> | ||
+ | <p> 2) Pick four colonies from the same plate as parallel repeats. Each colony is inoculated in two identical media with 5 ml LB medium containing 50 μg/mL kanamycin and cultured at temperature (37℃) respectively while shaking at 200 rpm. </p> | ||
+ | <p> 3) Measure the OD<sub>600</sub> value of the resuspension culture media in an automatic microplate reader (<b>Synergy</b><sup>TM</sup> H1 hybrid multimodal reader) until the OD<sub>600</sub> of the bacteria solution reaches 0.4-0.6. </p> | ||
<p> 4) Add IPTG to the bacteria solution of the experimental group to induce expression of the toxin proteins.</p> | <p> 4) Add IPTG to the bacteria solution of the experimental group to induce expression of the toxin proteins.</p> | ||
− | <p> 5) Plot the | + | <p> 5) Plot the OD<sub>600</sub> value curves of the resuspension culture media over time in an automatic microplate reader (<b>Synergy</b><sup>TM</sup> H1 hybrid multimodal reader). Incubate the cultures for 4 hours at 37℃ while shaking at 200 rpm. Take samples at intervals or continuously measure the OD<sub>600</sub> data of the bacteria solution with a UV spectrophotometer. And then convert the raw data into OD<sub>600</sub>. Compare the data of experimental groups and control group and compare curves in two schemes with each other.</p> |
<b>Toxin protein RelE CFU detection</b> | <b>Toxin protein RelE CFU detection</b> | ||
− | <p> 1) 1. Methods of molecular cloning and transformation are described above. Transform this plasmid into E. coli BL21. Then spread it onto LB medium plates with 50 μg/mL kanamycin and incubate overnight at | + | <p> 1) 1. Methods of molecular cloning and transformation are described above. Transform this plasmid into <i>E. coli</i> BL21(DE3). Then spread it onto LB medium plates with 50 μg/mL kanamycin and incubate overnight at 37℃ in an incubator.</p> |
− | <p> 2) Pick four colonies from the same plate as parallel repeats. Each colony is inoculated in two identical media with 5 ml LB medium containing 50 μg/mL kanamycin and cultured at temperature ( | + | <p> 2) Pick four colonies from the same plate as parallel repeats. Each colony is inoculated in two identical media with 5 ml LB medium containing 50 μg/mL kanamycin and cultured at temperature (37℃) respectively while shaking at 200 rpm.</p> |
− | <p> 3) Measure the | + | <p> 3) Measure the OD<sub>600</sub> value of the resuspension culture media in an automatic microplate reader (<b>Synergy</b><sup>TM</sup> H1 hybrid multimodal reader) until the OD<sub>600</sub> of the bacteria solution reaches 0.4-0.6. </p> |
− | <p> 4) Take samples every half hour, dilute the bacteria solution 1* | + | <p> 4) Take samples every half hour, dilute the bacteria solution 1*106 times, then spread it onto LB medium plates with 50 μg/mL kanamycin and incubate overnight at 37℃ in an incubator.</p> |
<p> 5)Count colonies on the plates cultured for the same time the next day, process the statistical data and plot the image.</p> | <p> 5)Count colonies on the plates cultured for the same time the next day, process the statistical data and plot the image.</p> | ||
− | ===Result | + | ====Result==== |
<html> | <html> | ||
<head> | <head> | ||
Line 48: | Line 146: | ||
<center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/rele2-1.jpg" style="width:50%; "></center> | <center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/rele2-1.jpg" style="width:50%; "></center> | ||
<br> | <br> | ||
− | <center><b>Figure | + | <center><b>Figure 5. Bacterial OD<sub>600</sub> over time .</b> </center> |
<br> | <br> | ||
Line 54: | Line 152: | ||
<center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/rele2-2-ab.jpg" style="width:80%; "></center> | <center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/rele2-2-ab.jpg" style="width:80%; "></center> | ||
<br> | <br> | ||
− | <center><b>Figure | + | <center><b>Figure 6. Viable cell counts over time.</b></center> |
+ | <br> | ||
+ | </body> | ||
+ | </html> | ||
+ | |||
+ | ====Analysis of the experimental results==== | ||
+ | Since RelE is a weak toxin protein, as shown in <b>Figure 5</b>, the OD<sub>600</sub> detection showed obvious inhibition of bacterial growth after induced expression, which delayed the log phase, but the bacteria could still grow in the later phase. The viable cell count method also produced significant results. As shown in <b>Figure 6</b>, viable cell counts decreased rapidly within one hour after induction, exhibiting significant growth inhibition, which demonstrated the bacteriostatic effect of this toxin. | ||
+ | |||
+ | ==Composite Elements Functional validation == | ||
+ | ===Combination element of RNA thermosensors regulatory RelE toxin protein=== | ||
+ | <b>The combination of two components can regulate the expression of toxin proteins by changing the temperature, and then control the death of engineering bacteria.</b> | ||
+ | ====Test Design ==== | ||
+ | we placed the RelE protein after the RNA thermosensor in the PUC57 plasmid and expressed the plasmid in <i>E. coli</i> BL21(DE3). Both control and treated groups were incubated at 37°C for 2.5 h and at 27℃ for 4.5 h, and the values of OD<sub>600</sub> were measured. | ||
+ | ====Test Protocol==== | ||
+ | <p> 1) Methods of molecular cloning and transformation are described above. Transform this plasmid into <i>E. coli</i> BL21(DE3). Then spread it onto LB medium plates with 170 μg/mL chloramphenicol and incubate overnight at 37℃ in an incubator. </p> | ||
+ | <p> 2) Pick four colonies from the same plate as parallel repeats. Each colony is inoculated in two identical media with 5 ml LB medium containing 170 μg/mL chloramphenicol and cultured at temperature (36℃) respectively while shaking at 200 rpm. </p> | ||
+ | <p> 3) Firstly,Measure the OD<sub>600</sub> value of the resuspension culture media in an automatic microplate reader (<b>Synergy</b><sup>TM</sup> H1 hybrid multimodal reader)for 2.5 hours at temperature (37℃),then Measure the OD<sub>600</sub> value of the resuspension culture media in an automatic microplate reader (<b>Synergy</b><sup>TM</sup> H1 hybrid multimodal reader) for 4.5 hours at temperature (27℃) </p> | ||
+ | <p> 4) Take samples at intervals or continuously measure the OD<sub>600</sub> data of the bacteria solution with a UV spectrophotometer. And then convert the raw data into OD<sub>600</sub>. Compare the data of experimental groups and control group and compare curves in two schemes with each other.</p> | ||
+ | |||
+ | ====Result==== | ||
+ | <html> | ||
+ | <head> | ||
+ | <meta charset="utf-8"> | ||
+ | <title>无标题文档</title> | ||
+ | </head> | ||
+ | <body> | ||
+ | <center><img src="https://static.igem.wiki/teams/4645/wiki/wet-lab/suicide/releax2.jpg" style="width:50%; "></center> | ||
+ | <br> | ||
+ | <center><b>Figure 7. The control and Treated groups were now incubated at 37℃ for 2.5 hours and then placed at 27℃ for 4.5 hours.</b> </center> | ||
<br> | <br> | ||
</body> | </body> | ||
</html> | </html> | ||
− | === | + | ====Analysis of the experimental results==== |
− | + | Changes in temperature can induce the expression of RelE toxin proteins as shown in <b>Figure 7</b>, the OD<sub>600</sub> detection showed obvious inhibition of bacterial growth after changed temperature, which delayed the log phase, but the bacteria could still grow in the later phase.At the same time the temperature also has some slight effect on the growth of the bacteria. |
Latest revision as of 15:57, 12 October 2023
Combination element of RNA thermosensors regulatory RelE toxin protein
RelE is a toxin protein that inhibits translation. RNA thermosensors which could inhibit downstream gene expression when the temperature is 37 ℃ but not affect downstream gene expression significantly when the temperature is below 28 ℃. The combination of two components can regulate the expression of toxin proteins by changing the temperature, and then control the death of engineering bacteria. The circuit is shown in the figure below.
Basic Elements
RNA thermosensors: This is one of heat-repressible RNA thermosensors which could inhibit downstream gene expression when the temperature is 37 ℃ but not affect downstream gene expression significantly when the temperature is below 26 ℃.
RelE toxin: The RelE toxin is an RNase that preferentially cleaves mRNAs bound to the ribosome at the second position of stop codons.
Basic Elements Functional validation
RNA thermosensors
To validate the function of the RNA thermosensor, we used two methods to experimentally verify it.
Test Design (Method 1)
First we placed the AmCyan protein after the RNA thermosensor in the PUC57 plasmid and expressed the plasmid in E. coli DH5α. After culturing for 4 hours continuously at 36℃, 26℃ and 16℃ respectively, the fluorescence intensity was detected and divided by the OD600 value, with DH5α cultured at 36℃ for 4 hours without plasmid transformation as control. The relative fluorescence intensity was detected to verify the function of the RNA thermosensor.
Test Protocol (Method 1)
1) Methods of molecular cloning and transformation are described above. Transform this plasmid into E. coli DH5α. Then spread it onto LB medium plates with 170 μg/mL chloramphenicol and incubate overnight at 37 ℃ in an incubator.
2) Pick four colonies from the same plate as parallel repeats. Each colony is inoculated in two identical media with 5 ml LB medium containing 170 μg/mL chloramphenicol and cultured at temperature (36 ℃) respectively while shaking at 200 rpm.
3) Measure the OD600 value of the resuspension culture media in an automatic microplate reader (SynergyTM H1 hybrid multimodal reader) until the OD600 of the bacteria solution reaches 0.4-0.6.
4) After grouping the samples, culture them continuously for 4 hours at 36℃, 26℃ and 16℃ respectively while shaking at 200 rpm.
5) Continuously measure fluorescence intensity (Exλ:453nm Emλ:486nm) and OD600 using an automatic microplate reader (SynergyTM H1 hybrid multimodal reader). After detection, divide the measured fluorescence intensity by OD600 to obtain the relative fluorescence intensity and analyze the results.
Result(Method 1)
Test Design (Method 2)
We referred to the verification method of iGEM21_HZAU-China BBa_K3733043 to verify the RNA thermosensor. We connected the toxin protein HepT after the RNA thermosensor and expressed it in E. coli DH5α using a plasmid.
Test Protocol (Method 2)
1) Methods of molecular cloning and transformation are described above. Transform this plasmid into E. coli DH5α. Then spread it onto LB medium plates with 170 μg/mL chloramphenicol and incubate overnight at 37 °C in an incubator.
2) Pick four colonies from the same plate as parallel repeats. Each colony is inoculated in two identical media with 5 ml LB medium containing 170 μg/mL chloramphenicol and cultured at temperature (37℃) respectively while shaking at 200 rpm overnight.
3) Measure the OD600 value of the resuspending culture media in an automatic microplate reader (SynergyTM H1 hybrid multimodal reader) until the OD600 of the bacteria solution reaches 0.4-0.6.
4) After grouping the samples, culture them continuously for 4 hours at 36℃ and 26℃ respectively, while shaking at 200 rpm.
5) Continuously measure fluorescence intensity (Exλ:453nm Emλ:486nm) and OD600 using an automatic microplate reader (SynergyTM H1 hybrid multimodal reader). After detection, divide the measured fluorescence intensity by OD600 to obtain the relative fluorescence intensity and analyze the results.
Result(Method 2)
Analysis of the experimental results
Results and analysis: Both verification methods successfully validated that the RNA thermosensor can function and express proteins at 26℃ or lower temperatures. However, the experimental results also showed that there was some leakage from the RNA thermosensor at 36℃, which may lead to some adverse effects.
Model
In order to gain a clearer understanding and validate the feasibility of the RNA thermosensor, we used DINAMelt's server for analysis of the neck ring structure.In the experiment, we obtained the fluorescence intensity of three points and assigned high weights to the experimental values, which in turn transformed into the probability of opening the loop. We have obtained the following graph Figure 4, which, although different from the open-loop probability graph we recognize, does indeed match the results of our experiment.
RelE toxin
To validate the function of the RelE toxin, we used two methods to experimentally verify it.
Test Design
In our experiment, we constructed a plasmid vector with RelE toxin protein connected after the lactose promoter and introduced it into E. coli BL21(DE3). IPTG was used to induce expression and OD600 was detected continuously for 4 hours. Samples were taken every 30 minutes, diluted and plated to determine viable cell counts.
Test Protocol
Toxin protein RelE OD600 detection
1) Methods of molecular cloning and transformation are described above. Transform this plasmid into E. coli BL21. Then spread it onto LB medium plates with 50 μg/mL kanamycin and incubate overnight at 37℃ in an incubator.
2) Pick four colonies from the same plate as parallel repeats. Each colony is inoculated in two identical media with 5 ml LB medium containing 50 μg/mL kanamycin and cultured at temperature (37℃) respectively while shaking at 200 rpm.
3) Measure the OD600 value of the resuspension culture media in an automatic microplate reader (SynergyTM H1 hybrid multimodal reader) until the OD600 of the bacteria solution reaches 0.4-0.6.
4) Add IPTG to the bacteria solution of the experimental group to induce expression of the toxin proteins.
5) Plot the OD600 value curves of the resuspension culture media over time in an automatic microplate reader (SynergyTM H1 hybrid multimodal reader). Incubate the cultures for 4 hours at 37℃ while shaking at 200 rpm. Take samples at intervals or continuously measure the OD600 data of the bacteria solution with a UV spectrophotometer. And then convert the raw data into OD600. Compare the data of experimental groups and control group and compare curves in two schemes with each other.
Toxin protein RelE CFU detection
1) 1. Methods of molecular cloning and transformation are described above. Transform this plasmid into E. coli BL21(DE3). Then spread it onto LB medium plates with 50 μg/mL kanamycin and incubate overnight at 37℃ in an incubator.
2) Pick four colonies from the same plate as parallel repeats. Each colony is inoculated in two identical media with 5 ml LB medium containing 50 μg/mL kanamycin and cultured at temperature (37℃) respectively while shaking at 200 rpm.
3) Measure the OD600 value of the resuspension culture media in an automatic microplate reader (SynergyTM H1 hybrid multimodal reader) until the OD600 of the bacteria solution reaches 0.4-0.6.
4) Take samples every half hour, dilute the bacteria solution 1*106 times, then spread it onto LB medium plates with 50 μg/mL kanamycin and incubate overnight at 37℃ in an incubator.
5)Count colonies on the plates cultured for the same time the next day, process the statistical data and plot the image.
Result
Analysis of the experimental results
Since RelE is a weak toxin protein, as shown in Figure 5, the OD600 detection showed obvious inhibition of bacterial growth after induced expression, which delayed the log phase, but the bacteria could still grow in the later phase. The viable cell count method also produced significant results. As shown in Figure 6, viable cell counts decreased rapidly within one hour after induction, exhibiting significant growth inhibition, which demonstrated the bacteriostatic effect of this toxin.
Composite Elements Functional validation
Combination element of RNA thermosensors regulatory RelE toxin protein
The combination of two components can regulate the expression of toxin proteins by changing the temperature, and then control the death of engineering bacteria.
Test Design
we placed the RelE protein after the RNA thermosensor in the PUC57 plasmid and expressed the plasmid in E. coli BL21(DE3). Both control and treated groups were incubated at 37°C for 2.5 h and at 27℃ for 4.5 h, and the values of OD600 were measured.
Test Protocol
1) Methods of molecular cloning and transformation are described above. Transform this plasmid into E. coli BL21(DE3). Then spread it onto LB medium plates with 170 μg/mL chloramphenicol and incubate overnight at 37℃ in an incubator.
2) Pick four colonies from the same plate as parallel repeats. Each colony is inoculated in two identical media with 5 ml LB medium containing 170 μg/mL chloramphenicol and cultured at temperature (36℃) respectively while shaking at 200 rpm.
3) Firstly,Measure the OD600 value of the resuspension culture media in an automatic microplate reader (SynergyTM H1 hybrid multimodal reader)for 2.5 hours at temperature (37℃),then Measure the OD600 value of the resuspension culture media in an automatic microplate reader (SynergyTM H1 hybrid multimodal reader) for 4.5 hours at temperature (27℃)
4) Take samples at intervals or continuously measure the OD600 data of the bacteria solution with a UV spectrophotometer. And then convert the raw data into OD600. Compare the data of experimental groups and control group and compare curves in two schemes with each other.
Result
Analysis of the experimental results
Changes in temperature can induce the expression of RelE toxin proteins as shown in Figure 7, the OD600 detection showed obvious inhibition of bacterial growth after changed temperature, which delayed the log phase, but the bacteria could still grow in the later phase.At the same time the temperature also has some slight effect on the growth of the bacteria.