College of Life Science and Technology, Beijing University of Chemical Technology, 15 Beisanhuan East Road, Chaoyang District, Beijing, 100029, China.
State Key Laboratory of Heavy Oil Processing, Institute of New Energy, China University of Petroleum, Beijing, 102249, China.
Chemosphere. 2018 Jun;200:93-105. doi: 10.1016/j.chemosphere.2018.02.100. Epub 2018 Feb 19.
Iron intoxications induce severe oxidative stress by producing reactive oxygen species (ROS) in cyanobacteria, leading to membrane lipid peroxidation, altered morphology, impaired photosynthesis and other oxidative stress injuries. Given these stresses, mitigation of ROS is a prerequisite for all aerobic organisms. Study of siderophilic cyanobacterium Leptolyngbya strain JSC-1 inhabiting iron-rich hot springs may provide insight into the mechanism of iron homeostasis and alleviation of oxidative stress. In this study, we investigated the morphophysiological and molecular mechanisms enabling this cyanobacterium to cope with iron-induced oxidative stress. Strain JSC-1 biomineralized extracellular iron via an exopolymeric sheath (acting as a first line of defense) and intracellular iron via polyphosphate inclusions (second line of defense), thus minimizing the burden of free ferric ions. Physiological parameters, SOD, CAT and POD activities, bacterioferritin and total protein contents fluctuated in response to iron elevation, displaying a third line of defense to mitigate ROS. Differential gene expression analysis of JSC-1 indicated up-regulation of 94 and 125 genes and down-regulation of 89 and 183 genes at low (4 μM) and high (400 μM) iron concentration, respectively. The differentially expressed genes (DEGs) were enriched in 100 KEGG pathways and were found to be involved in lipopolysaccharide and fatty acid biosynthesis, starch, sucrose, chlorophyll and other metabolic pathways. Together with metabolic reprogramming (fourth line of defense), JSC-1 established a unique multiline defense system that allows JSC-1 to withstand severe oxidative stress. These findings also provide insight into potential survival strategies of ancient microorganisms inhabiting similar environment present in early earth history.
铁中毒会通过在蓝藻中产生活性氧 (ROS) 而导致严重的氧化应激，从而导致膜脂质过氧化、形态改变、光合作用受损和其他氧化应激损伤。鉴于这些应激，ROS 的缓解是所有需氧生物的前提。研究栖息在富铁温泉中的嗜铁蓝藻 Leptolyngbya 菌株 JSC-1 可能有助于深入了解铁稳态和缓解氧化应激的机制。在这项研究中，我们研究了使这种蓝藻能够应对铁诱导的氧化应激的形态生理和分子机制。菌株 JSC-1 通过胞外聚合体鞘（作为第一道防线）和多磷酸盐内含物（第二道防线）生物矿化细胞外铁，从而最小化游离三价铁离子的负担。生理参数、SOD、CAT 和 POD 活性、细菌铁蛋白和总蛋白含量随铁浓度的升高而波动，表现出第三道防线以减轻 ROS。JSC-1 的差异基因表达分析表明，在低铁（4 μM）和高铁（400 μM）浓度下，分别有 94 个和 125 个基因上调，89 个和 183 个基因下调。差异表达基因（DEGs）富集在 100 个 KEGG 途径中，发现它们参与脂多糖和脂肪酸生物合成、淀粉、蔗糖、叶绿素和其他代谢途径。与代谢重编程（第四道防线）一起，JSC-1 建立了一个独特的多线防御系统，使 JSC-1 能够承受严重的氧化应激。这些发现还为研究栖息在早期地球历史上类似环境中的古代微生物的潜在生存策略提供了线索。
