Co-culturing and using cell-free filtrates are common methods for investigating allelopathy of marine phytoplankton; however, these methods often yield inconsistent or even contradictory results. The induced release of allelopathic compounds has been hypothesized as a mechanism to explain the discrepancy. Here, we used experiments to assess the inducibility of allelopathy by the diatom, Thalassiosira weissflogii, on the colony formation of Phaeocystis globosa. T. weissflogii and its cell-free filtrates showed inhibitory effects on the growth of solitary P. globosa cells. The colony number, colony diameter, and cells per colony decreased by co-occurring T. weissflogii cells but were enhanced by their extracellular filtrates alone. Live T. weissflogii cells possibly affect the colony integrity by reducing colonial cell density of P. globosa. When P. globosa and T. weissflogii were co-cultured but separated with a 2-µm membrane filter, thus allowing the exchange of extracellular secretions without direct cell contact, P. globosa colony concentration, colony diameter, cells per colony and colonial cell density were inhibited. Once T. weissflogii cells were pre-exposed to cell-free filtrates of P. globosa, their filtrates inhibited colony formation. T. weissflogii had allelopathic effects on P. globosa by releasing extracellular compounds that inhibited growth of solitary cells and colony formation, as well as disrupting colony integrity. However, the allelopathic effects of T. weissflogii on colony formation were only induced when the presence of P. globosa was perceived. Chemically mediated allelopathic effects of diatoms on colony formation of P. globosa may play an important role in the succession of diatoms and Phaeocystis.

中文翻译：

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拟南芥对化红囊藻集落形成的化感作用

共培养和使用无细胞滤液是调查海洋浮游植物化感作用的常用方法。但是，这些方法通常会产生不一致甚至矛盾的结果。据推测，化感物质的诱导释放是解释差异的机制。在这里，我们使用实验由硅藻，以评估化感作用的诱导性海链weissflogii，对集落形成的球形棕囊藻。T. weissflogii和其无细胞滤液显示出对孤的生长抑制作用P.藻细胞。共存的魏氏梭菌减少菌落数，菌落直径和每个菌落的细胞细胞，但仅通过细胞外滤液增强。活的T. weissflogii细胞可能通过降低P. globosa的菌落密度影响菌落的完整性。当共培养球藻和魏氏螺旋藻，但用2 µm膜滤器分离时，可以在没有直接细胞接触的情况下交换细胞外分泌物，球藻菌落浓度，菌落直径，每个菌落的细胞和菌落细胞密度被抑制。一旦T. weissflogii细胞被预先暴露于无球菌P. globosa的滤液中，它们的滤液就会抑制菌落的形成。T. weissflogii具有化感作用通过释放抑制单生细胞生长和菌落形成以及破坏菌落完整性的细胞外化合物，使球状疟原虫。然而，化感作用T. weissflogii上的集落形成，当存在的情况下仅诱导P.藻被察觉。化学介导的集落形成的硅藻的化感作用球形棕囊藻可能在硅藻和继承了重要的作用球形棕囊。