Understanding metabolic heterogeneity is critical for optimizing microbial production of valuable chemicals, but requires tools that can quantify metabolites at the single-cell level over time. Here, we develop longitudinal hyperspectral stimulated Raman scattering (SRS) chemical imaging to directly visualize free fatty acids in engineered Escherichia coli over many cell cycles. We also develop compositional analysis to determine the chain length and unsaturation of the fatty acids in living cells. Our method reveals substantial heterogeneity in fatty acid production among and within colonies that emerges over the course of many generations. Interestingly, the strains display distinct types of production heterogeneity in an enzyme-dependent manner. By pairing time-lapse and SRS imaging, we examine the relationship between growth and production at the single-cell level. Single-cell quantification does not show a significant growth-production tradeoff in a strain that exhibits high production heterogeneity. Our results demonstrate that cell-to-cell production heterogeneity is pervasive and provide a means to link single-cell and population-level production.

中文翻译：

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工程菌株的纵向单细胞化学成像揭示了脂肪酸生产的异质性

了解代谢异质性对于优化有价值化学品的微生物生产至关重要，但需要能够随时间在单细胞水平上量化代谢物的工具。在这里，我们开发了纵向高光谱受激拉曼散射 (SRS) 化学成像，以在多个细胞周期内直接可视化工程大肠杆菌中的游离脂肪酸。我们还开发了成分分析来确定活细胞中脂肪酸的链长和不饱和度。我们的方法揭示了在多代过程中出现的菌落之间和菌落内脂肪酸产生的显着异质性。有趣的是，这些菌株以酶依赖的方式表现出不同类型的生产异质性。通过配对延时和 SRS 成像，我们在单细胞水平检查生长和生产之间的关系。在表现出高生产异质性的菌株中，单细胞定量并未显示出显着的生长-生产权衡。我们的研究结果表明，细胞间生产异质性普遍存在，并提供了一种将单细胞和群体水平生产联系起来的方法。