Crosstalk between ROS Homeostasis and Secondary Metabolism in S. natalensis ATCC 27448: Modulation of Pimaricin Production by Intracellular ROS

Streptomyces secondary metabolism is strongly affected by oxygen availability. The increased culture aeration enhances pimaricin production in S. natalensis, however the excess of O2 consumption can lead to an intracellular ROS imbalance that is harmful to the cell. The adaptive physiological response of S. natalensis upon the addition of exogenous H2O2 suggested that the modulation of the intracellular ROS levels, through the activation of the H2O2 inducible catalase during the late exponential growth phase, can alter the production of pimaricin. With the construction of defective mutants on the H2O2 related enzymes SodF, AhpCD and KatA1, an effective and enduring modulation of intracellular ROS was achieved. Characterization of the knock-out strains revealed different behaviours regarding pimaricin production: whilst the superoxide dismutase defective mutant presented low levels of pimaricin production compared to the wild-type, the mutants defective on the H2O2-detoxifying enzymes displayed a pimaricin overproducer phenotype. Using physiological and molecular approaches we report a crosstalk between oxidative stress and secondary metabolism regulatory networks. Our results reveal that the redox-based regulation network triggered by an imbalance of the intracellular ROS homeostasis is also able to modulate the biosynthesis of pimaricin in S. natalensis.链霉菌（Streptomyces）的次级代谢过程显著受氧气供应状态的影响。提高培养通气量可提升纳塔尔链霉菌（Streptomyces natalensis）的匹马菌素（pimaricin）产量，但过量的氧气消耗会引发细胞内活性氧（Reactive Oxygen Species, ROS）失衡，对细胞产生毒害作用。纳塔尔链霉菌在添加外源过氧化氢（H₂O₂）后的适应性生理响应表明，在指数生长后期（late exponential growth phase）通过激活过氧化氢诱导型过氧化氢酶（catalase）调控细胞内活性氧水平，可改变匹马菌素的合成产量。本研究通过构建针对过氧化氢相关酶超氧化物歧化酶F（SodF）、烷基过氧化氢还原酶CD（AhpCD）及过氧化氢酶A1（KatA1）的缺陷突变株（defective mutant），成功实现了对细胞内活性氧的有效且持久的调控。对这些敲除菌株（knock-out strain）的表型表征显示，其匹马菌素合成能力呈现出显著差异：与野生型（wild-type）菌株相比，超氧化物歧化酶缺陷突变株的匹马菌素产量较低，而过氧化氢解毒酶缺陷突变株则表现出匹马菌素高产表型。本研究借助生理学与分子生物学手段，揭示了氧化应激（oxidative stress）与次级代谢调控网络之间的串扰现象。研究结果表明，由细胞内活性氧稳态（homeostasis）失衡引发的氧化还原调控网络，同样能够调控纳塔尔链霉菌中匹马菌素的生物合成。