Picocyanobacteria (cells <2 µm) can be found either as single-cells (Pcy) or embedded in a mucilaginous sheath as microcolonies or colonies (CPcy). It has been demonstrated that phenotypic plasticity in picocyanobacteria (i.e. the capability of single-cells to aggregate into colonies) can be induced as a response to grazing pressure. The effect of the presence of different predators (cladocerans and rotifers) over the morphological composition of picocyanobacteria were studied in a natural community, and it was observed that the abundance of CPcy significantly increased in all treatments with zooplankton with respect to the Control without zooplankton. The aggregation capability was also evaluated in a single-cell strain, by adding conditioned medium of flagellates, rotifers and cladocerans. The proportion of cells forming colonies was significantly higher in all treatments with conditioned medium regardless the predator. These results suggest that the aggregation of Pcy can be induced as a response of the predation pressure exerted by protists and different zooplankters, and also that Pcy has the capability to aggregate into CPcy even without a direct contact with any predator, most probably due to the presence of an infochemical dissolved into the water that would not come from disrupted Pcy cells.

中文翻译：

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蓝藻细菌聚集作为捕食压力的响应：不需要直接接触。

微型蓝细菌（细胞<2 µm）可以单细胞（Pcy）的形式发现，也可以微菌落或菌落（CPcy）的形式包埋在粘膜鞘中。已经证明，作为对放牧压力的响应，可以诱导微蓝细菌中的表型可塑性（即单细胞聚集到菌落中的能力）。在一个自然群落中研究了不同捕食者（cladocerans和轮虫）的存在对微蓝细菌形态组成的影响，并且观察到，与没有浮游动物的对照相比，在所有浮游动物处理中，CPcy的含量均显着增加。还通过添加鞭毛，轮虫和锁角形的条件培养基，在单细胞菌株中评估了聚集能力。不论掠食者如何，在所有用条件培养基处理的情况下，形成菌落的细胞比例均显着较高。这些结果表明，Pcy的聚集可作为对原生生物和不同的浮游动物施加的捕食压力的响应而诱发，并且即使没有与任何捕食者直接接触，Pcy仍具有聚集成CPcy的能力，这很可能是由于溶解在水中的信息化学物质的存在，并非来自破坏了的Pcy细胞。