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. 2011 Sep 29;7(9):e1002172. doi: 10.1371/journal.pcbi.1002172

Figure 3. Separating the AI-2 uptake into sub-networks.

Figure 3

A) The first sub-network is made by the removal of lsr-operon from luxS knock-out strains. As the concentration of AI-2 increases, more AI-2-P is available to bind LsrR resulting in higher transcription from the lsr-operon promoter. The maximum expression level is reached by hour 5 when most of AI-2 is taken up by the cell. Hereafter, external AI-2 is depleted and the expression levels of all dose responses decline as cells enter the stationary phase. B) The second sub-network is made by the removal of lsrR gene from the bacterial genome. The expression of levels of lsr-operon is still somewhat dependent on AI-2 despite the fact that there is no LsrR to repress the lsr-operon. C) The lsrK knock-out represent the third sub-network where in the absence of the LsrK kinase, LsrR completely represses the lsr-operon.