重新思考细菌糖代谢中的选择行为
Rethinking the Choice Behavior of Sugar Metabolism in Bacteria
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中文总结 AI 辅助
研究重新思考细菌糖代谢选择行为，将其转化为微观经济的消费者选择问题，通过线性规划在蛋白质组预算约束下最大化生长效用，用单底物实验参数再现细菌生长，揭示顺序底物使用是一般结果，共同利用是退化情况。
中文摘要 AI 辅助
Ramkrishna、Kompala和Tsao提出了微生物生长的控制论模型，其中细胞根据模仿理性决策的匹配规则分配酶合成资源。后来发现该匹配规则在关于潜在投资回报率结构的一般假设下是最优的，但细胞最大化的具体目标以及限制该选择的约束条件从未被明确写成一个明确的经济决策。在此，我们补充了这个缺失的决策，将控制论酶合成控制重新表述为微观经济理论中的消费者选择问题：细胞在竞争性分解代谢酶之间分配有限的蛋白质组预算作为线性规划（LP），在蛋白质组预算约束下最大化线性生长效用。由于效用是线性的，LP的解是几何的：只要等效用线的斜率与预算约束的斜率不同，最优解就是一个角点，整个蛋白质组预算就分配给最有利可图的单一底物的酶。角点解对应于二次生长，底物的顺序消耗源于角点的选择而非独特的调节机制。只有当两个斜率重合时，最优解才会分布在整个预算线上而不是集中在单个角点；这种退化情况是同时使用底物的基础。仅使用从单底物实验独立估计的参数，LP推导的控制论变量就再现了产酸克雷伯菌在葡萄糖-木糖和葡萄糖-木糖-乳糖混合物上的二次和三次分批生长，拟合效果与经典匹配定律相当。因此，在完全可替代的情况下，顺序底物使用是生长最大化专业化的一般结果，而共同利用是同等盈利能力的退化情况。
英文摘要
Ramkrishna, Kompala, and Tsao proposed the cybernetic model of microbial growth, in which cells allocate enzyme synthesis resources according to a matching rule that mimics rational decision-making. The matching rule was later shown to be optimal under general assumptions about the underlying return-on-investment structure, yet the specific objective the cell maximizes, and the constraints bounding that choice, were never written down as an explicit economic decision. Here we supply that missing decision, recasting cybernetic enzyme-synthesis control as a consumer choice problem from microeconomic theory: the cell allocates a limited proteome budget among competing catabolic enzymes as a linear program (LP), maximizing a linear growth utility subject to a linear proteome budget constraint. Because the utility is linear, the LP's solution is geometric: whenever the iso-utility line's slope differs from the budget constraint's, the optimum is a corner, and the entire proteome budget is allocated to the enzyme for the single most profitable substrate. Corner solutions correspond to diauxic growth, and sequential substrate consumption follows from the choice of corner rather than a distinct regulatory mechanism. Only when the two slopes coincide does the optimum spread across the entire budget line instead of concentrating at a single corner; this degenerate case underlies simultaneous substrate use. Using only parameters estimated independently from single-substrate experiments, the LP-derived cybernetic variables reproduced the diauxic and triauxic batch growth of Klebsiella oxytoca on glucose-xylose and glucose-xylose-lactose mixtures, achieving a fit comparable to the classical matching law. Thus, sequential substrate use is the generic outcome of growth-maximizing specialization under perfect substitutability, and co-utilization is the degenerate case of equal profitability.
