Harmful algal bloom (HAB) is an unresolved existing problem worldwide. Here, we reported a novel algicidal bacterium, YB2, capable of lysing multiple algal species. To , YB2 exhibited a maximum algicidal rate of 95.02 % at 120 h. The uniqueness of YB2 lies in its ability to self-produce three algicidal compounds: 2-methyl-1, 3-cyclohexanedione (2-MECHD), N-phenyl-2-naphthylamine, and cyclo (Pro-Leu). The algicidal properties of 2-MECHD have not been previously reported. YB2 significantly affected the chloroplast and mitochondrion, thus decreasing in chlorophyll by 4.74 times for 120 h and succinate dehydrogenase activity by 103 times for 36 h. These physiological damages disrupted reactive oxygen species and Ca homeostasis at the cellular level, increasing cytosolic superoxide dismutase (23 %), catalase (35 %), and Ca influx. Additionally, the disruption of Ca homeostasis rarely reported in algicidal bacteria–algae interaction was observed using the non-invasive micro-test technology. We proposed a putative algicidal mechanism based on the algicidal outcomes and physiological algicidal effects and explored the potential of YB2 through an algicidal simulation test. Overall, this study is the first to report the algicidal bacterium and identify a novel algicidal compound, 2-MECHD, providing new insights and a potent microbial resource for the biocontrol of HAB.

中文翻译：

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新发现的一种杀藻细菌Pseudomonas fragi YB2：杀藻化合物及其作用


有害藻华（HAB）是世界范围内尚未解决的现有问题。在这里，我们报道了一种新型杀藻细菌 YB2，能够裂解多种藻类。 YB2在120 h时的最大杀藻率达到95.02%。 YB2的独特之处在于它能够自行产生三种杀藻化合物：2-甲基-1, 3-环己二酮（2-MECHD）、N-苯基-2-萘胺和环（Pro-Leu）。 2-MECHD 的杀藻特性此前尚未有报道。 YB2显着影响叶绿体和线粒体，导致叶绿素在120小时内下降4.74倍，琥珀酸脱氢酶活性在36小时内下降103倍。这些生理损伤破坏了细胞水平的活性氧和 Ca 稳态，增加了胞质超氧化物歧化酶 (23%)、过氧化氢酶 (35%) 和 Ca 内流。此外，使用非侵入性微测试技术观察到在杀藻细菌-藻类相互作用中很少报道的钙稳态破坏。我们根据杀藻结果和生理杀藻效应提出了一种假定的杀藻机制，并通过杀藻模拟测试探索了YB2的潜力。总体而言，这项研究首次报道了杀藻细菌，并鉴定了一种新型杀藻化合物 2-MECHD，为 HAB 的生物防治提供了新的见解和有效的微生物资源。