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. Author manuscript; available in PMC: 2012 May 20.
Published in final edited form as: Mol Cell. 2011 May 20;42(4):413–425. doi: 10.1016/j.molcel.2011.04.016

Figure 1. How do bacteria resolve conflicts in gene regulation caused by simultaneous exposure to two different drugs?

Figure 1

(A) Schematic example for a conflict in gene regulation: Promoter X is down-regulated in response to drug A, but up-regulated in response to drug B. How is promoter X regulated when the cell is faced with a combination of both drugs A and B? (B) In the combination of two drugs, cells may linearly superpose the response to the individual drugs (‘averaged response’, top row) or respond only to one of the drugs while ignoring the presence of the other drug (‘prioritized response’, middle row), depending on the concentration ratio of the two drugs. In a prioritized response, both drugs may affect the cell’s response equally (middle row) or one of the drugs may have a stronger impact on the response (‘biased response’, bottom row; the response is biased towards drug A in the example shown). Down-regulation is indicated by white cell-interior, up-regulation by green. (C) At the single cell level, all cells may show the same response to the drug combination (‘deterministic response’, left) or different cells may randomly respond primarily to only one of the drugs in the combination (‘stochastic response’, right).