Bacteria grown on a mixture of carbon substrates exhibit two utilization patterns: hierarchical utilization (HU) and simultaneous utilization (SU). How and why cells adopt these different behaviors remains poorly understood despite decades of research. Recent studies address various open questions from multiple viewpoints. From a mechanistic perspective, it was found that flux sensors play a central role in the regulation of substrate utilization, accounting for the known dependences on single-substrate growth rates, substrate concentrations, and the point where the substrate enters central metabolism. From a physiological perspective, several recent studies suggested HU or SU as growth-optimizing strategies through efficient allocation of essential proteome resources. However, other studies demonstrate that a significant fraction of the proteome is dedicated to functions apparently unnecessary for growth, casting doubt on explanations based on slight efficiency gains. From an ecological perspective, recent theoretical studies suggest that HU can help increase species diversity in bacterial communities.

在碳底物混合物上生长的细菌表现出两种利用模式：分级利用 (HU) 和同时利用 (SU)。尽管进行了数十年的研究，但细胞如何以及为何采取这些不同的行为仍然知之甚少。最近的研究从多个角度解决了各种开放性问题。从机制的角度来看，发现通量传感器在底物利用的调节中起着核心作用，解释了已知的对单一底物生长速率、底物浓度和底物进入中央代谢的点的依赖性。从生理学的角度来看，最近的几项研究表明 HU 或 SU 通过有效分配必需的蛋白质组资源作为生长优化策略。然而，其他研究表明，蛋白质组的很大一部分专用于生长显然不必要的功能，这对基于轻微效率增益的解释提出了质疑。从生态学的角度来看，最近的理论研究表明，HU 可以帮助增加细菌群落的物种多样性。