The fundamental details of how nutritional stress leads to elevating (p)ppGpp are questionable. By common usage, the meaning of the stringent response has evolved from the specific response to (p)ppGpp provoked by amino acid starvation to all responses caused by elevating (p)ppGpp by any means. Different responses have similar as well as dissimilar positive and negative effects on gene expression and metabolism. The different ways that different bacteria seem to exploit their capacities to form and respond to (p)ppGpp are already impressive despite an early stage of discovery. Apparently, (p)ppGpp can contribute to regulation of many aspects of microbial cell biology that are sensitive to changing nutrient availability: growth, adaptation, secondary metabolism, survival, persistence, cell division, motility, biofilms, development, competence, and virulence. Many basic questions still exist. This review tries to focus on some issues that linger even for the most widely characterized bacterial strains.

中文翻译：

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（p）ppGpp：还神奇吗？

营养压力如何导致（p）ppGpp升高的基本细节值得怀疑。通常，严格应答的含义已从对氨基酸饥饿引起的对（p）ppGpp的特异性应答演变为通过任何方式升高（p）ppGpp引起的所有应答。不同的响应对基因表达和代谢具有相同或不同的正面和负面影响。尽管处于早期发现阶段，但不同细菌似乎利用其形成和响应（p）ppGpp能力的不同方式已经令人印象深刻。显然，（p）ppGpp有助于调节微生物细胞生物学的许多方面，这些方面对养分利用率的变化非常敏感：生长，适应，次级代谢，存活，持久性，细胞分裂，运动性，生物膜，发育，能力，和毒力。仍然存在许多基本问题。这篇综述试图将重点放在即使对于最广泛表征的细菌菌株仍然存在的问题上。