Phagotrophy by a flagellate selects for colonial prey: A possible origin of multicellularity
Phagotrophy by a flagellate selects for colonial prey: A possible origin of multicellularity
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DOI：
10.1023/a:1006527528063
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发表时间：
1998-02-01
影响因子：
1.9
通讯作者：
Boxhorn, JE
中科院分区：
文献类型：
--
作者：
Boraas, ME;Seale, DB;Boxhorn, JE
捕食是一种强大的选择性力量，促使在恒定环境条件下保持的单细胞猎物的形态复杂性增加。绿藻普通小球藻是一种被广泛研究的真核生物，在我们实验室的培养中保持了正常的单细胞形态已有数千代。在本文所报道的实验中，将捕食性鞭毛虫Ochromonas vallescia(一种食性鞭毛原生动物)接种于连续培养的单细胞普通隐翅虫。在不到100代的猎物中，多细胞小球藻的生长形式在培养中占主导地位(随后在其他培养中重复)。猎物小球藻首先形成由数十到数百个细胞组成的球状集群。在吞噬菌存在的情况下，经过大约10-20代后，八细胞集落占主导地位。这些菌落在连续培养和接种到琼脂上时，无限期地保留了八细胞形态。这些自我复制、稳定的菌落几乎对鞭毛虫的捕食具有免疫力，但足够小，以至于每个小球藻细胞都直接暴露在营养介质中。
Predation was a powerful selective force promoting increased morphological complexity in a unicellular prey held in constant environmental conditions. The green alga, Chlorella vulgaris, is a well-studied eukaryote, which has retained its normal unicellular form in cultures in our laboratories for thousands of generations. For the experiments reported here, steady-state unicellular C. vulgaris continuous cultures were inoculated with the predator Ochromonas vallescia, a phagotrophic flagellated protist (`flagellate'). Within less than 100 generations of the prey, a multicellular Chlorella growth form became dominant in the culture (subsequently repeated in other cultures). The prey Chlorella first formed globose clusters of tens to hundreds of cells. After about 10-20 generations in the presence of the phagotroph, eight-celled colonies predominated. These colonies retained the eight-celled form indefinitely in continuous culture and when plated onto agar. These self-replicating, stable colonies were virtually immune to predation by the flagellate, but small enough that each Chlorella cell was exposed directly to the nutrient medium.