Numerous prokaryotes accumulate polyhydroxybutyrate (PHB) intracellularly as a storage material. It has also been proposed that PHB accumulation improves bacterial stress resistance. Cupriavidus necator and its PHB non-accumulating mutant were employed to investigate the protective role of PHB under hypertonic conditions. The presence of PHB granules enhanced survival of the bacteria after exposure to hypertonic conditions. Surprisingly, when coping with such conditions, the bacteria did not utilize PHB to harvest carbon or energy, suggesting that, in the osmotic upshock of C. necator, the protective mechanism of PHB granules is not associated with their hydrolysis. The presence of PHB granules influenced the overall properties of the cells, since challenged PHB-free cells underwent massive plasmolysis accompanied by damage to the cell membrane and the leakage of cytoplasm content, while no such effects were observed in PHB containing bacteria. Moreover, PHB granules demonstrated "liquid-like" properties indicating that they can partially repair and stabilize cell membranes by plugging small gaps formed during plasmolysis. In addition, the level of dehydration and changes in intracellular pH in osmotically challenged cells were less pronounced for PHB-containing cultures, demonstrating the important role of PHB for bacterial survival under hyperosmotic conditions.

中文翻译：

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细胞质中 PHB 颗粒的存在保护非嗜盐细菌细胞免受高渗环境的有害影响

许多原核生物在细胞内积累聚羟基丁酸 (PHB) 作为储存材料。也有人提出 PHB 的积累可以提高细菌的抗逆性。Cupriavidus necator 及其 PHB 非积累突变体被用来研究 PHB 在高渗条件下的保护作用。在暴露于高渗条件后，PHB 颗粒的存在提高了细菌的存活率。令人惊讶的是，在应对这种情况时，细菌并没有利用 PHB 来收集碳或能量，这表明，在 C. necator 的渗透性上震中，PHB 颗粒的保护机制与其水解无关。PHB 颗粒的存在影响了细胞的整体特性，由于受到挑战的不含 PHB 的细胞经历了大规模的质壁分离，伴随着细胞膜的损伤和细胞质内容物的泄漏，而在含有 PHB 的细菌中没有观察到这种影响。此外，PHB 颗粒表现出“液体状”特性，表明它们可以通过堵塞质壁分离过程中形成的小间隙来部分修复和稳定细胞膜。此外，对于含有 PHB 的培养物，渗透性挑战细胞的脱水水平和细胞内 pH 值的变化不太明显，证明了 PHB 在高渗条件下对细菌存活的重要作用。特性表明它们可以通过堵塞质壁分离过程中形成的小间隙来部分修复和稳定细胞膜。此外，对于含有 PHB 的培养物，渗透性挑战细胞中的脱水水平和细胞内 pH 值的变化不太明显，证明了 PHB 在高渗条件下对细菌存活的重要作用。特性表明它们可以通过堵塞质壁分离过程中形成的小间隙来部分修复和稳定细胞膜。此外，对于含有 PHB 的培养物，渗透性挑战细胞的脱水水平和细胞内 pH 值的变化不太明显，证明了 PHB 在高渗条件下对细菌存活的重要作用。