Team:SDSZ China/Improve

iGem SDSZ_China 2018


All these benefits of quorum sensing is not included in BBa_K2380044, although it is able to produce CDA
To optimise the production of chitosan, we decide to employ the Quorum-Sensing System, which can regulate the gene expression in a density dependent manner. The density dependent property of QS System can be extremely beneficial to us, since we want the bacteria to express heterogeneous gene CDA and produce chitosan when the bacteria density reaches a relatively high level. As the total amount of energy inside the bacterial cell is constant, when bacteria are growing, their CDA expression will be reduced, while bacterial proliferation will be hindered when they allocate more energy in CDA expression. Therefore, Quorum-Sensing system can act as a switch to us: when the density is low, the CDA is inactive, allowing the bacteria to put into more energy in growth and reproduce; in contrast, when the density reaches a threshold, the CDA is activated, leading to higher expression level of CDA.
Improvement: In fermentation, we need to constantly measure the density of the bacteria to determine whether the threshold density (quorum) is reached or not. As a result, fermenting with the regulation of Quorum-Sensing can be time-consuming. To eliminate the need of waiting and constantly measuring, we decide to use IPTG concentration to decide the threshold density directly and the bacteria would switch the stage of expression automatically.
The detailed part of improvement can be checked in Experiment A and Experiment B part. Although we did not utilize snap genes to exclude all the possible enzyme digestion site CTGCAG, we optimized codons into CTCCAG(1315bp) without interfering proteins function.