Understanding the Molecular Mechanisms of Pyrene in Governing the Critical Metabolic Circuits of Alexandrium pacificum

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 Alexandrium pacificum, a dinoflagellate responsible for harmful algal blooms, and their capability to bioremove pyrene. In a 96 h exposure experiment, A. pacificum 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 A. pacificum 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 A. pacificum. 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 A. pacificum's response to pyrene, reveal the impact of pyrene on PST synthesis, and suggest that A. pacificum holds significant potential for pyrene biodegradation.