Thraustochytrids are particle-associated protists, ubiquitous in the marine environment. They are known to display a negative relationship with phytoplankton cells but a positive one with their exudates and detritus. Phytoplankton are known to express allelopathic effects against other organisms, but the exact mechanism by which phytoplankton cause inhibition to thraustochytrids is understudied. This is the first report of examination of bioactivity of lipid extracts of diatom cultures on thraustochytrids. Lipid extracts from four diatom cultures, viz. Cylindrotheca closterium (JB2), Skeletonema sp.1 (JB3), Thalassiosira sp. (JB4) and Skeletonema sp.2 (JB5), were tested against the growth of thraustochytrids: Oblongichytrium spp. (isolates VD4 and VD6), Parietichytrium sp. (isolate VD12) and Schizochytrium sp. (isolate VDC23b). Among the thraustochytrid isolates, Parietichytrium sp. was the most sensitive, whereas Schizochytrium sp. appeared to be the most resistant to the lipid extracts. The lipid extract from C. closterium possessed high amounts of C16:0, C16:1, C18:0, C18:1 and C20:5 fatty acids and bioactivity against the thraustochytrids. Lipids extracted during the late stationary phase of diatoms were inhibitory to thraustochytrid growth. Overall, these observations not only enhance our understanding of the diversity of allelopathic interactions between thraustochytrids and diatoms in the marine ecosystem, but also reveal the pivotal role of diatom lipids in such interactions across trophic levels.

中文翻译：

---

海洋真菌原生生物破囊壶菌对硅藻脂质提取物反应的初步研究

破囊壶菌是与颗粒相关的原生生物，在海洋环境中无处不在。已知它们与浮游植物细胞呈负相关，但与它们的分泌物和碎屑呈正相关。已知浮游植物对其他生物表达化感作用，但浮游植物对破囊壶菌的抑制作用的确切机理尚未得到研究。这是第一个检查硅藻培养物中脂质提取物对破囊壶菌的生物活性的报告。来自四种硅藻培养物的脂质提取物，即。Cylindrotheca closterium（JB2），Skeletonema sp.1（JB3），Thalassiosira sp。（JB4）和Skeletonema sp.2（JB5）已针对破囊壶菌的生长进行了测试：扁线虫属 （隔离VD4和VD6），Parietichytrium sp。（隔离VD12）和Schizochytrium sp。（隔离VDC23b）。在破囊壶菌的分离物中，Parietichytrium sp。是最敏感的，而裂殖壶菌属。似乎对脂质提取物最有抵抗力。梭状芽胞杆菌的脂质提取物拥有大量的C16：0，C16：1，C18：0，C18：1和C20：5脂肪酸，并且具有抗破囊壶菌的生物活性。在硅藻的稳定期后期提取的脂质可抑制破囊壶菌的生长。总体而言，这些观察结果不仅增进了我们对海洋生态系统中破囊壶菌和硅藻之间的化感相互作用的多样性的理解，而且揭示了硅藻脂质在营养级的这种相互作用中的关键作用。