Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5A, 02-106, Warsaw, Poland.
Department of Food Chemistry and Biotechnology, Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00, Brno, Czech Republic.
Appl Microbiol Biotechnol. 2024 Mar 23;108(1):273. doi: 10.1007/s00253-024-13092-8.
An ever-growing body of literature evidences the protective role of polyhydroxyalkanoates (PHAs) against a plethora of mostly physical stressors in prokaryotic cells. To date, most of the research done involved bacterial strains isolated from habitats not considered to be life-challenging or extremely impacted by abiotic environmental factors. Polar region microorganisms experience a multitude of damaging factors in combinations rarely seen in other of Earth's environments. Therefore, the main objective of this investigation was to examine the role of PHAs in the adaptation of psychrophilic, Arctic-derived bacteria to stress conditions. Arctic PHA producers: Acidovorax sp. A1169 and Collimonas sp. A2191, were chosen and their genes involved in PHB metabolism were deactivated making them unable to accumulate PHAs (ΔphaC) or to utilize them (Δi-phaZ) as a carbon source. Varying stressors were applied to the wild-type and the prepared mutant strains and their survival rates were assessed based on CFU count. Wild-type strains with a functional PHA metabolism were best suited to survive the freeze-thaw cycle - a common feature of polar region habitats. However, the majority of stresses were best survived by the ΔphaC mutants, suggesting that the biochemical imbalance caused by the lack of PHAs induced a permanent cell-wide stress response thus causing them to better withstand the stressor application. Δi-phaZ mutants were superior in surviving UV irradiation, hinting that PHA granule presence in bacterial cells is beneficial despite it being biologically inaccessible. Obtained data suggests that the ability to metabolize PHA although important for survival, probably is not the most crucial mechanism in the stress-resistance strategies arsenal of cold-loving bacteria. KEY POINTS: • PHA metabolism helps psychrophiles survive freezing • PHA-lacking psychrophile mutants cope better with oxidative and heat stresses • PHA granule presence enhances the UV resistance of psychrophiles.
越来越多的文献证据表明，聚羟基脂肪酸酯（PHA）对原核细胞中大多数物理胁迫具有保护作用。迄今为止，大多数研究涉及的细菌菌株均来自于那些被认为不会对生命构成挑战或受生物环境因素影响较小的栖息地。极地微生物在其所处环境中会经历多种组合的破坏性因素，而这些因素在地球上其他环境中很少见。因此，本研究的主要目的是研究 PHA 在适应嗜冷、来自北极的细菌应对应激条件中的作用。选择了北极 PHA 生产者：食酸菌（Acidovorax sp. A1169）和胶态康氏杆菌（Collimonas sp. A2191），并使其 PHB 代谢相关基因失活，从而无法积累 PHA（ΔphaC）或利用 PHA 作为碳源（Δi-phaZ）。将不同的胁迫因素应用于野生型和准备好的突变菌株，并根据 CFU 计数评估它们的存活率。具有功能性 PHA 代谢的野生型菌株最适合在冻融循环中存活，这是极地栖息地的一个共同特征。然而，大多数应激因素最适合由 ΔphaC 突变体存活，这表明缺乏 PHA 引起的生化失衡导致了永久性的全细胞应激反应，从而使它们能够更好地承受应激因素的应用。Δi-phaZ 突变体在耐 UV 照射方面表现出色，这表明 PHA 颗粒在细菌细胞中的存在是有益的，尽管它在生物学上无法接近。获得的数据表明，尽管代谢 PHA 的能力对生存很重要，但它可能不是嗜冷细菌应激抗性策略库中最关键的机制。关键点：•PHA 代谢有助于嗜冷菌在冷冻时存活•缺乏 PHA 的嗜冷菌突变体更好地应对氧化和热应激•PHA 颗粒的存在增强了嗜冷菌的抗 UV 能力。
