title: Noise-induced switches in network systems of the genetic toggle switch.
abstract: BACKGROUND
  Bistability, the capacity to achieve two distinct stable steady states in response to a set of external stimuli, arises within biological systems ranging from the lambda phage switch in bacteria to cellular signal transduction pathways in mammalian cells. On the other hand, more and more experimental evidence in the form of bimodal population distribution has indicated that noise plays a very important role in the switching of bistable systems. However, the physiological mechanism underling noise-induced switching behaviors remains to be fully understood.
  
  
  RESULTS
  In this paper, we investigate the effect of noises on switching in single and coupled genetic toggle switch systems in Escherichia coli. In the case of the single toggle switch, we show that the multiplicative noises resulting from stochastic fluctuations in degradation rates can induce switching. In the case of the toggle switches interfaced by a quorum-sensing signaling pathway, we find that stochastic fluctuations in degradation rates inside cells, i.e., intracellular noises, can induce synchronized switching, whereas the extracellular noise additive to the common medium can not only entrain all the individual systems to switch in a synchronous manner but also enhance this ordering behavior efficiently, leading a robust collective rhythm in this interacting system.
  
  
  CONCLUSIONS
  These insights on the effect of noises would be beneficial to understanding the basic mechanism of how living systems optimally facilitate to function under various fluctuated environments.
authors.affiliation: State Key Laboratory of Biocontrol and Guangzhou Center for Bioinformatics, School of Life Science, Sun Yat-Sen University, Guangzhou, PR China. wangjunweilj@yahoo.com.cn
authors.forename: Junwei
authors.initials: J
authors.lastname: Wang
authors.forename: Jiajun
authors.initials: J
authors.lastname: Zhang
authors.forename: Zhanjiang
authors.initials: Z
authors.lastname: Yuan
authors.forename: Tianshou
authors.initials: T
authors.lastname: Zhou