Many bacteria produce storage biopolymers that are mobilized under conditions of metabolic adaptation, for example, low nutrient availability and cellular stress. Polyhydroxyalkanoates are often found as carbon storage in Bacteria or Archaea, and of these polyhydroxybutyrate (PHB) is the most frequently occurring PHA type. Bacteria usually produce PHB upon availability of a carbon source and limitation of another essential nutrient. Therefore, it is widely believed that the function of PHB is to serve as a mobilizable carbon repository when bacteria face carbon limitation, supporting their survival. However, recent findings indicate that bacteria switch from PHB synthesis to mobilization under stress conditions such as thermal and oxidative shock. The mobilization products, 3-hydroxybutyrate and its oligomers, show a protective effect against protein aggregation and cellular damage caused by reactive oxygen species and heat shock. Thus, bacteria should have an environmental monitoring mechanism directly connected to the regulation of the PHB metabolism. Here, we review the current knowledge on PHB physiology together with a summary of recent findings on novel functions of PHB in stress resistance. Potential applications of these new functions are also presented.

中文翻译：

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PHB 及其降解产物对细菌应激情况的保护作用。


许多细菌产生储存生物聚合物，这些生物聚合物在代谢适应条件下被动员起来，例如，低营养可用性和细胞应激。聚羟基链烷酸酯通常作为细菌或古细菌中的碳储存而被发现，其中聚羟基丁酸酯 (PHB) 是最常见的 PHA 类型。细菌通常在碳源可用且另一种必需营养素有限的情况下产生 PHB。因此，人们普遍认为PHB的功能是在细菌面临碳限制时充当可移动的碳库，支持其生存。然而，最近的研究结果表明，细菌在热休克和氧化休克等应激条件下从 PHB 合成转变为动员。动员产物 3-羟基丁酸酯及其低聚物对活性氧和热休克引起的蛋白质聚集和细胞损伤具有保护作用。因此，细菌应该具有与PHB代谢调节直接相关的环境监测机制。在这里，我们回顾了有关 PHB 生理学的最新知识，并总结了 PHB 在抗应激方面的新功能的最新发现。还介绍了这些新功能的潜在应用。