Modeling on the suicide mechanism of the reporter system

To eliminate potential safety problem, we constructed a suicide system on engineered bacteria to ensure biosafety. As the only one loaded with kill switch, the engineered reporter bacteria is responsible for eliminating all siblings in T-vaccine. Killing is mediated by the exported toxic protein SdpC. Extracellular SdpC induces the synthesis of an immunity protein, SdpI, which protects toxin-producing cells from being killed. SdpI, a polytopic membrane protein, is encoded by a two-gene operon under sporulation control that contains the gene for an autorepressor, SdpR.

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The best growing condition for Bacillus subtilis WB800N

To ensure the expression of our T-vaccine, we do some experiments to find out the best growing condition for Bacillus subtilis WB800N, we finally choose five independent factors: temperature, inoculation time, peptone, yeast extract and NaCl. The following table displays their levels:

Factor	Low	High
Temperature	25℃	35℃
Time	12h	24h
Peptone	5	15
Yeast Extract	2.5	7.5
NaCl	5	15

Roughly, we could consider the treatment of No. 15 medium (Temperature 35℃, Time 12h, Peptone 15, Yeast Extract 7.5, NaCl 15)as the maximal condition for Bacillus subtilis.
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Designs of Immune Experiments

Our mice experiment has primarily proven the validity of our project. However, just like most scientific immune experiments on animals, the aim of our mice experiment was verification instead of exploring the optimal conditions for the production of our vaccine. In fact, fewer optimization experiments have been done by pure scientific researches, as most scientists care about facts and theories only, whereas exploring the optimal conditions is often viewed as the task of pharmaceutical factories. Yet since igem itself frequently involves industrial fields, which make igem seems like more an engineering competition than a science competition sometimes.

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