a generic mechanism for adaptive growth rate regulation一个通用的自适应增长速度调节的机制.pdfVIP

A Generic Mechanism for Adaptive Growth Rate Regulation Chikara Furusawa1,2*, Kunihiko Kaneko2,3 1 Department of Bioinformatics Engineering, Graduate School of Information Science and Technology, Osaka University, Suita, Osaka, Japan, 2 Complex Systems Biology Project, ERATO, JST, Komaba, Meguro-ku, Tokyo, Japan, 3 Department of Pure and Applied Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo, Japan How can a microorganism adapt to a variety of environmental conditions despite the existence of a limited number of signal transduction mechanisms? We show that for any growing cells whose gene expression fluctuate stochastically, the adaptive cellular state is inevitably selected by noise, even without a specific signal transduction network for it. In general, changes in protein concentration in a cell are given by its synthesis minus dilution and degradation, both of which are proportional to the rate of cell growth. In an adaptive state with a higher growth speed, both terms are large and balanced. Under the presence of noise in gene expression, the adaptive state is less affected by stochasticity since both the synthesis and dilution terms are large, while for a nonadaptive state both the terms are smaller so that cells are easily kicked out of the original state by noise. Hence, escape time from a cellular state and the cellular growth rate are negatively correlated. This leads to a selection of adaptive states with higher growth rates, and model simulations confirm this selection to take place in general. The results suggest a general form of adaptation that has never been brought to light—a process that requires no specific mechanisms for sensory adaptation. The present scheme may help explain a wide range of cellular adaptive responses including the metabolic flux optimization for maximal cell growth. Citation: Furusawa C, Kaneko K (2008) A generic mechanism for adaptive growth rate regulation.