Laboratory of Aquatic Pathobiology, Environmental and Marine Biology, Department of Biosciences, Åbo Akademi University, Tykistökatu 6, FIN-20520 Turku, Finland.
Microb Pathog. 2012 Nov-Dec;53(5-6):214-8. doi: 10.1016/j.micpath.2012.08.004. Epub 2012 Aug 27.
The cytotoxic activity of smooth and rough phenotypic cells of the fish pathogenic Gram-negative bacterium Flavobacterium psychrophilum to rainbow trout (Oncorhynchus mykiss) head kidney macrophages was investigated in vitro. The cytotoxicity to macrophages was significantly higher for rough cells compared with the smooth cells. The cytotoxic activity increased for both cell types with increasing temperature and the cells retained their cytotoxic nature after metabolical inactivation by heat, suggesting a cell-bound cytotoxic mechanism. The cytotoxicity was significantly reduced in both cell types after treatment with sodium (meta)periodate, indicating that the major bacterial structure involved in the cytotoxicity is of carbohydrate nature. Trypsin treatment further reduced the cytotoxicity in smooth cells, while sialic acid treatment reduced the cytotoxicity in rough cells, suggesting different lysing mechanisms for the two phenotypic variants. The results from the present study therefore suggest that the cytotoxic activity of F. psychrophilum to rainbow trout macrophages in vitro is stronger expressed in the rough phenotype and that it is opsonin-independent and initiated by binding of bacterial surface carbohydrates to lectins on the surface of the macrophages. How the lysis of the macrophages is executed is still unclear but it is suggested to function by different mechanisms in the smooth and the rough cells. The migration of rainbow trout macrophages toward smooth and rough cells of F. psychrophilum was further investigated. The results show that the macrophages were able to recognize both cell types, but the migration rate did not differ between the two phenotypes.
本研究调查了鱼类病原菌嗜冷性杀鲑气单胞菌光滑型和粗糙型细胞对虹鳟头肾巨噬细胞的体外细胞毒性。与光滑型细胞相比，粗糙型细胞对巨噬细胞的细胞毒性明显更高。两种细胞类型的细胞毒性均随温度升高而增加，并且细胞经热代谢失活后仍保持其细胞毒性，表明存在细胞结合的细胞毒性机制。两种细胞类型经（偏）高碘酸钠处理后，细胞毒性均显著降低，表明与细胞毒性相关的主要细菌结构具有碳水化合物性质。经胰蛋白酶处理后，光滑型细胞的细胞毒性进一步降低，而唾液酸处理后粗糙型细胞的细胞毒性降低，表明两种表型变体的裂解机制不同。因此，本研究结果表明，嗜冷性杀鲑气单胞菌对虹鳟巨噬细胞的体外细胞毒性在粗糙型中表达更强，并且该毒性是补体非依赖性的，由细菌表面碳水化合物与巨噬细胞表面的凝集素结合引发。巨噬细胞的裂解机制尚不清楚，但据推测，光滑型和粗糙型细胞的裂解机制不同。本研究进一步研究了虹鳟巨噬细胞向嗜冷性杀鲑气单胞菌光滑型和粗糙型细胞的迁移。结果表明，巨噬细胞能够识别两种细胞类型，但两种表型之间的迁移率没有差异。
