Understanding the Molecular Mechanisms of Pyrene in Governing the Critical Metabolic Circuits of <i>Alexandrium pacificum</i>

Pyrene, a representative polycyclic aromatic hydrocarbon, frequently occurs in aquatic environments and is associated with lethal impacts on humans and wildlife. This study examined the impact of pyrene on <i>Alexandrium pacificum</i>, a dinoflagellate responsible for harmful algal blooms, and their capability to bioremove pyrene. In a 96 h exposure experiment, <i>A. pacificum</i> effectively reduced the pyrene concentration in seawater to 50, 100, and 200 μg/L, with a combined removal efficiency of 96% in seawater. Furthermore, the study noted a significant reduction in the synthesis of GTX4, GTX1, NEO, and GTX3 toxins in <i>A. pacificum</i> cells exposed to 50 and 200 μg/L of pyrene. Concurrently, exposure to pyrene resulted in marked declines in the growth and photosynthetic efficiency of <i>A. pacificum</i>. Proteomics analysis results showed an upregulation of proteins related to endocytosis, such as HSPA and Arf, while proteins associated with paralytic shellfish toxin (PST) synthesis, specifically SxtU and SxtH, showed a downregulation trend. In summary, the findings of this study preliminarily elucidate the molecular mechanisms underlying <i>A. pacificum</i>'s response to pyrene, reveal the impact of pyrene on PST synthesis, and suggest that <i>A. pacificum</i> holds significant potential for pyrene biodegradation.