Polyhydroxyalkanoates are essential for maintenance of redox state in the Antarctic bacterium Pseudomonas sp 14-3 during low temperature adaptation
Polyhydroxyalkanoates are essential for maintenance of redox state in the Antarctic bacterium Pseudomonas sp 14-3 during low temperature adaptation
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DOI：
10.1007/s00792-008-0197-z
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发表时间：
2009-01-01
期刊：
影响因子：
2.9
通讯作者：
Lopez, Nancy I.
中科院分区：
文献类型：
--
作者：
Ayub, Nicolas D.;Tribelli, Paula M.;Lopez, Nancy I.
聚羟基脂肪酸酯 (PHA) 是一种高度减少细菌储存的化合物，可提高在不断变化的环境中的适应性。我们之前已经证明来自南极细菌假单胞菌的 phaRBAC 基因。 14-3位于基因组岛中，其中包含可能与其对寒冷环境的适应性有关的其他基因。在本文中，假单胞菌属 sp。 14-3 及其 PHA 合成酶缺失突变体 (phaC) 用于评估 PHA 积累对寒冷条件适应性的影响。 phaC 突变体无法在 10°C 下生长，并且比其亲本菌株更容易受到冷冻的影响。 PHA 对于冷处理诱导的氧化应激反应的发展是必需的。添加还原化合物胱氨酸和谷胱甘肽抑制了 phaC 突变体的冷敏感表型。冷激使野生型菌株中的 PHA 快速降解。通过二酰胺敏感性估计的 NADH/NAD 比率和 NADPH 含量在冷休克后在突变体中强烈下降，而在野生型中仅观察到微小变化。因此，温度降低后，突变株中的脂质过氧化水平提高了 25 倍。我们认为 PHA 代谢调节还原当量的可用性，有助于减轻低温产生的氧化应激。
Polyhydroxyalkanoates (PHAs) are highly reduced bacterial storage compounds that increase fitness in changing environments. We have previously shown that phaRBAC genes from the Antarctic bacterium Pseudomonas sp. 14-3 are located in a genomic island containing other genes probably related with its adaptability to cold environments. In this paper, Pseudomonas sp. 14-3 and its PHA synthase-minus mutant (phaC) were used to asses the effect of PHA accumulation on the adaptability to cold conditions. The phaC mutant was unable to grow at 10A degrees C and was more susceptible to freezing than its parent strain. PHA was necessary for the development of the oxidative stress response induced by cold treatment. Addition of reduced compounds cystine and gluthathione suppressed the cold sensitive phenotype of the phaC mutant. Cold shock produced very rapid degradation of PHA in the wild type strain. The NADH/NAD ratio and NADPH content, estimated by diamide sensitivity, decreased strongly in the mutant after cold shock while only minor changes were observed in the wild type. Accordingly, the level of lipid peroxidation in the mutant strain was 25-fold higher after temperature downshift. We propose that PHA metabolism modulates the availability of reducing equivalents, contributing to alleviate the oxidative stress produced by low temperature.