Higuchi Rina, Song Chihong, Hoshina Ryo, Suzaki Toshinobu
Department of Biology, Graduate School of Science, Kobe University, Nada-ku, Kobe 657-8501, Japan.
Department of Biology, Graduate School of Science, Kobe University, Nada-ku, Kobe 657-8501, Japan; National Institute for Physiological Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi, 444-8787, Japan.
Eur J Protistol. 2018 Oct;66:149-155. doi: 10.1016/j.ejop.2018.09.003. Epub 2018 Sep 19.
Chlorella variabilis, a symbiotic alga, is usually present in the cytoplasm of Paramecium bursaria, although it can be cultured in host-free conditions. Morphological and chemical properties of its cell wall were compared between its free-living and symbiotic states. Transmission electron microscopy (quick-freezing and freeze-substitution methods) revealed that the cell wall thickness of symbiotic C. variabilis was reduced to about half that of the free-living one. Chemical properties of the cell wall were examined by treatment with three fluorescent reagents (calcofluor white M2R, FITC-WGA, and FITC-LFA) having specific binding affinities to different polysaccharides. When the algae were re-introduced into Paramecium host cells, calcofluor fluorescence intensity reduced by about 50%. Calcofluor stains β-d-glucopyranose polysaccharides such as cellulose, N-acetylglucosamine, sialic acid, and glycosaminoglycans. Because treatment with cellulase showed no effect on calcofluor fluorescence intensity, we consider that cellulose is not majorly responsible for the stainability of calcofluor. Staining intensities of FITC-WGA and FITC-LFA were similar in the free-living and symbiotic conditions, suggesting that N-acetylglucosamine and sialic acid are also not responsible for the reduction in the stainability of calcofluor associated with intracellular symbiosis. The amount of glycosaminoglycans on the cell wall may decrease in C. variabilis present in the cytoplasm of P. bursaria.
可变小球藻是一种共生藻类，通常存在于草履虫的细胞质中，不过它也能在无宿主条件下培养。我们比较了其细胞壁在自由生活状态和共生状态下的形态和化学性质。透射电子显微镜（快速冷冻和冷冻置换法）显示，共生的可变小球藻的细胞壁厚度降至自由生活状态下的约一半。通过用三种对不同多糖具有特异性结合亲和力的荧光试剂（荧光增白剂M2R、异硫氰酸荧光素标记的小麦胚凝集素和异硫氰酸荧光素标记的扁豆凝集素）处理来检测细胞壁的化学性质。当藻类重新引入草履虫宿主细胞时，荧光增白剂的荧光强度降低了约50%。荧光增白剂可染色β - D - 吡喃葡萄糖多糖，如纤维素、N - 乙酰葡糖胺、唾液酸和糖胺聚糖。由于用纤维素酶处理对荧光增白剂的荧光强度没有影响，我们认为纤维素并非荧光增白剂染色性的主要原因。在自由生活和共生条件下，异硫氰酸荧光素标记的小麦胚凝集素和异硫氰酸荧光素标记的扁豆凝集素的染色强度相似，这表明N - 乙酰葡糖胺和唾液酸也不是与细胞内共生相关的荧光增白剂染色性降低的原因。存在于草履虫细胞质中的可变小球藻细胞壁上的糖胺聚糖量可能会减少。
