Abstract Harmful bloom-forming algae include some of the most prolific microbial producers of extracellular reactive oxygen species (ROS). However, the taxonomic diversity of ROS production, the underlying physiological mechanisms and ecophysiological roles of ROS cycling are not completely characterized among phytoplankton taxa that form harmful algal blooms (HABs). This study examines the extracellular production of the ROS superoxide and hydrogen peroxide by five marine HAB species: Chattonella marina, Heterosigma akashiwo, Karenia brevis, Pseudo-nitzschia sp. and Aureococcus anophagefferens. All species produced extracellular superoxide and hydrogen peroxide. Rates of ROS production per cell spanned several orders of magnitude and varied inversely with cell density, suggesting a potential signaling role for extracellular ROS. ROS production was also detected in the spent media of all cultures except K. brevis, indicating the presence of cell-free ROS-generating constituents, such as enzymes or metabolites, which could be further investigated as molecular targets for tracking ROS production in laboratory and field settings. Finally, ratios of superoxide to hydrogen peroxide production could not be accounted for by superoxide dismutation alone, except in the case of K. brevis, indicating a diversity of ROS production and degradation pathways that may ultimately help illuminate the functions of HAB-derived ROS.

中文翻译：

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五种海洋有害藻类产生细胞外超氧化物和过氧化氢

摘要 有害的水华形成藻类包括一些最多产的细胞外活性氧 (ROS) 微生物生产者。然而，在形成有害藻华（HAB）的浮游植物类群中，ROS产生的分类多样性、ROS循环的潜在生理机制和生态生理作用尚未完全表征。本研究检查了五种海洋 HAB 物种细胞外产生的 ROS 超氧化物和过氧化氢：Chattonella marina、Heterosigma akashiwo、Karenia brevis、Pseudo-nitzschia sp。和无噬金球菌。所有物种都产生细胞外超氧化物和过氧化氢。每个细胞的 ROS 产生率跨越几个数量级，并且与细胞密度成反比变化，表明细胞外 ROS 具有潜在的信号传导作用。除 K. brevis 外，所有培养物的废培养基中也检测到 ROS 产生，表明存在无细胞 ROS 生成成分，例如酶或代谢物，可以将其作为跟踪实验室和实验室中 ROS 产生的分子目标进行进一步研究。字段设置。最后，超氧化物与过氧化氢产生的比率不能仅通过超氧化物歧化来解释，除了短短杆菌的情况外，这表明 ROS 产生和降解途径的多样性，可能最终有助于阐明 HAB 衍生的 ROS 的功能。