Instituto Tecnológico de Chascomús (INTECH), UNSAM-CONICET. Av. Intendente Marino Km 8,200, (7130) Chascomús, Buenos Aires, Argentina.
Instituto Nacional de Limnología (INALI), CONICET-UNL. Ciudad Universitaria - Paraje el Pozo s/n, (3000) Santa Fé, Argentina.
FEMS Microbiol Ecol. 2020 Oct 2;96(10). doi: 10.1093/femsec/fiaa153.
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) on the morphological composition of picocyanobacteria was studied in a natural community, and it was observed that the abundance of CPcy significantly increased in all treatments with zooplankton compared with the control without zooplankton. The aggregation capability was also evaluated in a single-cell strain by adding a conditioned medium of flagellates, rotifers and cladocerans. The proportion of cells forming colonies was significantly higher in all treatments with conditioned medium regardless of the predator. These results suggest that the aggregation of Pcy can be induced as a response to the predation pressure exerted by protists and different zooplankters, and also that Pcy has the capability to aggregate into CPcy even without direct contact with any predator, most probably due to the presence of an infochemical dissolved in the water that does not come from disrupted Pcy cells.
微囊藻（细胞 <2 µm）可以以单细胞（Pcy）形式存在，也可以嵌入黏液鞘中形成微菌落或菌落（CPcy）。已经证明，微囊藻的表型可塑性（即单细胞聚集形成菌落的能力）可以作为对摄食压力的反应而被诱导。在一个自然群落中研究了不同捕食者（枝角类和轮虫）对微囊藻形态组成的影响，结果观察到与无浮游动物的对照组相比，所有有浮游动物的处理组中 CPcy 的丰度显著增加。还通过添加鞭毛虫、轮虫和枝角类的条件培养基来评估单细胞菌株的聚集能力。无论捕食者如何，所有有条件培养基的处理组中形成菌落的细胞比例都明显更高。这些结果表明，Pcy 的聚集可以作为对原生动物和不同浮游动物施加的捕食压力的反应而被诱导，而且 Pcy 即使没有与任何捕食者直接接触也具有聚集形成 CPcy 的能力，这很可能是由于水中存在一种信息素，而这种信息素不是来自被破坏的 Pcy 细胞。
