The peptidoglycan (PG), as the exoskeleton of most prokaryotes, maintains a defined shape and ensures cell integrity against the high internal turgor pressure. These important roles have attracted researchers to target PG metabolism in order to control bacterial infections. Most studies, however, have been performed in bacteria grown under laboratory conditions, leading to only a partial view on how the PG is synthetized in natural environments. As a case in point, PG metabolism and its regulation remain poorly understood in symbiotic and pathogenic bacteria living inside eukaryotic cells. This review focuses on the PG metabolism of intracellular bacteria, emphasizing the necessity of more in vivo studies involving the analysis of enzymes produced in the intracellular niche and the isolation of PG from bacteria residing within eukaryotic cells. The review also points to persistent infections caused by some intracellular bacterial pathogens and the extent at which the PG could contribute to establish such physiological state. Based on recent evidences, I speculate on the idea that certain structural features of the PG may facilitate attenuation of intracellular growth. Lastly, I discuss recent findings in endosymbionts supporting a cooperation between host and bacterial enzymes to assemble a mature PG.

中文翻译：

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在真核细胞内构建肽聚糖：共生和致病细菌的观点。

作为大多数原核生物的外骨骼，肽聚糖（PG）保持确定的形状并确保细胞完整性抵抗高内部膨胀压力。这些重要作用吸引了研究人员靶向PG代谢，以控制细菌感染。但是，大多数研究都是在实验室条件下生长的细菌中进行的，因此仅部分了解了如何在自然环境中合成PG。举个例子，在真核细胞内部的共生和致病细菌中，PG的代谢及其调控仍然知之甚少。这篇综述着重于细胞内细菌的PG代谢，强调需要进行更多体内研究，包括分析细胞内利基中产生的酶以及从真核细胞中分离细菌PG。该评论还指出了由某些细胞内细菌病原体引起的持续感染，以及PG在多大程度上有助于建立这种生理状态。基于最近的证据，我推测PG的某些结构特征可能促进细胞内生长的减弱。最后，我讨论了内共生体的最新发现，这些共生体支持宿主酶和细菌酶之间的协作以组装成熟的PG。