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| − | <a class="card" href="https://2018.igem.org/Team:FJNU-China/Collaborations">
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| − | <div class="front" style="background-image: url(https://static.igem.org/mediawiki/2018/c/ce/T--FJNU-China--overview-3.png);">
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| − | <p style="font-size: 40px;">Collaboration</p>
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| − | <p>We collaborated with many other iGEM teams during the course of our project, with whom we set up good friendship and keep communication. Besides, we helped each other to measure some data. Here we want to show our sincere gratitude to them.</p>
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| − | <button class="button">Click Here</button>
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| − | <h2> Mechanism of PLA</h2>
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| − | <h4>Effect of different concentration of PLA on the number of Staphylococcus epidermidis.</h3>
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| − | <p ><span style="font-size:25px;font-weight:bold;">Introduce</span></br> we had planned to established a dynamic equation to describe the effect of PLA on <span style=" font-style:italic;">staphylococcus epidermidis</span> which is the main bacteria that cause the armpit order. We gave several candidate forms of function for describing this process and finally found the best one which fit the experimental data quite well. By using the data from the experiment，we continually refine our models and guide our project through this models. Besides, this model, of which type has never been built before, also makes us learning the mechanism of PLA and solved problems as following:</br>
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| − | (1) How many PLA should we put in our products that can kill the desired amount of <span style=" font-style:italic;">staphylococcus epidermidis</span>?</br>
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| − | (2) What is the effect of concentration of PLA on the number of <span style=" font-style:italic;">staphylococcus epidermidis</span>over time.</br>（3)What is the growth of bacteria at any concentration of PLA?
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| − | <p ><span style="font-size:25px;font-weight:bold;">Method</span></br> To solve the problems above, we used different concentration of PLA to react with Staphylococcus epidermidis, then we measured the rest of bacteria every hour for a total of 8 hours. Through fitting the initial data, we got the following chary and found the appropriate function to describe this figure.
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| − | <a class="lightbox" href="https://static.igem.org/mediawiki/2018/d/de/T--FJNU-China--Interlab-figue12.png">
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| − | <img src="https://static.igem.org/mediawiki/2018/d/de/T--FJNU-China--Interlab-figue12.png" alt="table1">
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| − | <p><span style="font-size:25px;"> dx/dt=(-1.0836*(t-1.4028) ^2+1.7601) *x(t) -(a*dCp ^n)*x(t)</br>
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| − | dCp=Cp-Cp*</span>
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| − | Through this model, we have known that PLA would not have any effect on the bacteria until reaching a certain concentration, so we designed two parts of equation for this model
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| − | <p><span style="font-size:25px;">(1) Cp<Cp*</br>
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| − | dx/dt=[-a(t-b)2+c] * x(t)
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| − | </span></br> When the concentration of PLA in the system are less than the critical value, the bacteria are able to grow naturally, so we use a dynamic equation of growth rate of Staphylococcus epidermidis.</p>
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| − | <p ><span style="font-size:20px;font-weight:bold;">(2) Cp>Cp*</br>
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| − | △Cp=Cp-Cp*</br>
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| − | dx/dt= f(△Cp) *x(t)</br>
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| − | f(△Cp) = ax<span style="vertical-align:super;">n</span>
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| − | </span></br> In this situation, Cp more than the value of Cp*, PLA has an inhibitory effect on Staphylococcus epidermidis. The mortality is set as f(△Cp) and the death rate are expressed by dx/dt= f(△Cp) *x(t).
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| − | According to the data analysis, mortality should meet the following two conditions:</br>
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| − | ①The function value should increase with the value of (Cp- Cp*), and the function need to be super linear.</br>
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| − | ②When Cp -Cp*=0，the value of f(△Cp) should equal to zero.</br>
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| − | From the above conditions, we set the f(△Cp) as the exponential function: ax<span style="vertical-align:super;">n</span></br>
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| − | By combining these two formulas, we can describe the survival of <span style="text-align:italic;">Staphylococcus epidermidis </span>at different PLA concentrations over time. And we have concluded that the PLA concentration is 6.7106mmol/l, which has an inhibitory effect on the epidermidis.
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| − | <p><span style="font-size:25px;font-weight:bold;">Expand
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| − | </span></br> In order to verity if there is a multiple relationship between inhibitions of PLA on different amounts of bacteria. We changed the parameter value of starting optical density equal to 2kbs and 0.5kbs, then we got the figures as following and concluded the same critical value of PLA. Later, we have used experiment to verity those charts correct.</p>
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| − | <a class="lightbox" href="https://static.igem.org/mediawiki/2018/d/de/T--FJNU-China--Interlab-figue12.png">
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| − | <img src="https://static.igem.org/mediawiki/2018/d/de/T--FJNU-China--Interlab-figue12.png" alt="table1">
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| − | </a>
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| − | <p> Through these two figure, we have learned that the same concentration of PLA has the same effect on the different number of bacteria, which means that PLA kill the bacteria in proportion to the whole population. This conclusion proves that the formula about applies to any number of bacteria.</p>
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| − | <p><span style="font-size:25px;font-weight:bold;">Optimize
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| − | </span></br> Based on the above formulas, we had obtained the range of the critical value and lethality of PLA preliminarily, which has instructed the following experiment. We subdivided the PLA concentration in the above range to make it work on Staphylococcus epidermidis to validated the model and obtained more accurate parameters.</p>
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| − | <p><span style="font-size:25px;font-weight:bold;">Achievements
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| − | </span></br> ①Using 6.7106mmol/l PLA will have an inhibitory effect on Staphylococcus epidermidis.</br>
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| − | ②PLA mechanism: kill bacteria in the proportion.</br>
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| − | ③Any kinds of bacteria can grow naturally in a certain range of concentration of PLA under the critical value, which can be used in screening and isolation of strains.
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| − | <h2> PLA yield curve</h2>
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| − | <p ><span style="font-size:25px;font-weight:bold;">Introduce</span></br> we have established a dynamic equation to describe the yield of PLA. Since the synthesis of PLA requires the design of enzymatic reactions, we designed the mistral equation for this purpose and reshaped it by our experimental data. This model allows us to understand the relationship between different bacteria counts and PLA production，which effectively solving the following problem:
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| − | if our system can produce the desired amount of PLA?
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| − | </p>
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| − | <p ><span style="font-size:25px;font-weight:bold;">Method</span></br> Before we built model, we had used different number of BM4R to produce PLA. We sufficient substrates for the whole reaction and measured the amount of production every 20 minutes. Based on our experiment data and the principle of PLA metabolic pathway, we select a function similar to the mistral equation to fit our experimental data.
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| − | </p>
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| − | <img src="https://static.igem.org/mediawiki/2018/7/75/T--FJNU-China--models-method1.png" style="width:25%">
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| − | <p>Based on the above model, we have known that when the substrate is sufficient and a certain amounts of bacteria is input at a certain time point, with the continuous accumulation of PLA output, the synthesis rate of PLA gradually decreases. When P reaches Pm, PLA is no longer produced and maintains a stable yield.</p>
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| − | <p ><span style="font-size:25px;font-weight:bold;">Achievement</span></br> (1) Let us Know how many engineered bacteria should be used and at what time that the required amount of PLA can be obtained, saving time and materials to facilitate commercialization.</br>
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| − | (2) It illustrates the mechanism why the amount of PLA could be the same under different excessive substrate concentrations even through the formation rate of PLA might be significant different
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| − | </p>
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| | <h2> Application of models</h2> | | <h2> Application of models</h2> |
