All microsporidia share a unique, extracellular spore stage, containing the infective sporoplasm and the apparatus for initiating infection. The polar filament/polar tube when exiting the spore transports the sporoplasm through it into a host cell. While universal, these structures and processes have been enigmatic. This study utilized several types of microscopy, describing and extending our understanding of these structures and their functions. Cryogenically preserved polar tubes vary in diameter from 155 to over 200 nm, noticeably larger than fixed‐sectioned or negatively stained samples. The polar tube surface is pleated and covered with fine fibrillar material that projects from the surface and is organized in clusters or tufts. These fibrils may be the sites of glycoproteins providing protection and aiding infectivity. The polar tube surface is ridged with 5–6 nm spacing between ridges, enabling the polar tube to rapidly increase its diameter to facilitate the passage of the various cargo including cylinders, sacs or vesicles filled with particulate material and the intact sporoplasm containing a diplokaryon. The lumen of the tube is lined with a membrane that facilitates this passage. Careful examination of the terminus of the tube indicates that it has a closed tip where the membranes for the terminal sac are located.

中文翻译：

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Anncaliia algerae（小孢子虫）挤压极管的超微结构研究

所有微孢子虫都有一个独特的细胞外孢子阶段，包含感染性孢子质和引发感染的装置。当离开孢子时，极丝/极管将孢子质通过它输送到宿主细胞中。虽然普遍，但这些结构和过程一直是神秘的。这项研究使用了几种类型的显微镜，描述并扩展了我们对这些结构及其功能的理解。低温保存的极管直径从 155 纳米到超过 200 纳米不等，明显大于固定切片或负染色样品。极管表面打褶并覆盖有从表面突出并组织成簇或簇的细纤维状材料。这些原纤维可能是提供保护和辅助感染性的糖蛋白位点。极管表面以 5-6 nm 的脊间距排列，使极管能够迅速增加其直径，以促进各种货物的通过，包括充满颗粒物质的圆柱体、囊或囊泡以及含有双核体的完整孢子质。管腔衬有促进该通道的膜。仔细检查管子的末端表明它有一个封闭的尖端，末端囊的膜位于此处。管腔衬有促进该通道的膜。仔细检查管子的末端表明它有一个封闭的尖端，末端囊的膜位于此处。管腔衬有促进该通道的膜。仔细检查管子的末端表明它有一个封闭的尖端，末端囊的膜位于此处。