Venturelli Ophelia S, Zuleta Ignacio, Murray Richard M, El-Samad Hana
Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, United States of America; Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America; The California Institute for Quantitative Biosciences, University of California San Francisco, San Francisco, California, United States of America.
Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America; The California Institute for Quantitative Biosciences, University of California San Francisco, San Francisco, California, United States of America.
PLoS Biol. 2015 Jan 27;13(1):e1002042. doi: 10.1371/journal.pbio.1002042. eCollection 2015 Jan.
Delineating the strategies by which cells contend with combinatorial changing environments is crucial for understanding cellular regulatory organization. When presented with two carbon sources, microorganisms first consume the carbon substrate that supports the highest growth rate (e.g., glucose) and then switch to the secondary carbon source (e.g., galactose), a paradigm known as the Monod model. Sequential sugar utilization has been attributed to transcriptional repression of the secondary metabolic pathway, followed by activation of this pathway upon depletion of the preferred carbon source. In this work, we demonstrate that although Saccharomyces cerevisiae cells consume glucose before galactose, the galactose regulatory pathway is activated in a fraction of the cell population hours before glucose is fully consumed. This early activation reduces the time required for the population to transition between the two metabolic programs and provides a fitness advantage that might be crucial in competitive environments.
描绘细胞应对组合变化环境的策略对于理解细胞调节组织至关重要。当面对两种碳源时，微生物首先消耗支持最高生长速率的碳底物（例如葡萄糖），然后切换到次要碳源（例如半乳糖），这是一种被称为莫诺德模型的范例。顺序性糖利用归因于次要代谢途径的转录抑制，随后在首选碳源耗尽时该途径被激活。在这项工作中，我们证明，尽管酿酒酵母细胞在消耗半乳糖之前先消耗葡萄糖，但在葡萄糖完全消耗前数小时，一部分细胞群体中的半乳糖调节途径就已被激活。这种早期激活减少了群体在两种代谢程序之间转换所需的时间，并提供了一种适应性优势，这在竞争环境中可能至关重要。
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