枯草芽孢杆菌中色噪声诱导的ComK基因表达动力学

Kinetics of ComK Gene Expression Induced by Colored Noises in Bacillus subtilis

枯草芽孢杆菌(Bacillus subtilis)包含耦合的正负反馈环路,通过转录因子ComK的信号通路感知环境噪声波动,因此,研究噪声强度和自关联时间诱导下ComK表达动力学性质能有效揭示芽孢杆菌的演化进程。本研究观察了ComK表达系统中色噪声诱导蛋白质浓度转换的现象,根据诺维科夫理论和福克斯近似方法,计算出稳态概率分布函数的近似表达式。在此基础上应用最陡下降法计算出平均首通时间的近似表达式,分析了乘性噪声和加性噪声的强度及其自关联时间对稳态概率分布和平均首通时间的影响。结果表明,在不同乘性噪声和加性噪声的噪声强度下,平均首通时间会随着自关联时间的增大而变小,说明噪声强度和自关联时间会引起蛋白质浓度经历“开”→“关”的转换。

Bacillus subtilis contains coupled positive and negative feedback loops and senses environmental noise fluctuations through the signaling pathway of transcription factor ComK.Therefore,a study on the dynamics of ComK expression induced by noise intensity and autocorrelation time can effectively reveal the evolutionary process of B.subtilis.An attempt was made to analyze the phenomenon of protein concentration conversion induced by color noise in ComK expression system.According to Novikov theory and Fox approximation method,the approximate expression of the steady-state probability distribution function is given,and the approximate expression of the mean first passage time is calculated by using the steepest descent method.The effects of the noise intensity and the autocorrelation time of the multiplicative noise and additive noise on the steady-state probability distribution and the mean first passage time are analyzed.The results show that under different noise intensities of multiplicative noise and additive noise,the mean first passage time decreases with the increase of autocorrelation time,which indicates that the noise intensity and autocorrelation time will cause the protein concentration to go through the transition from“on”to“off”.