CRYO-ELECTRON TOMOGRAPHY OF GIARDIA INTESTINALIS

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。所列机构为 中心，不一定是研究者的机构。 贾第鞭毛虫（Giardia lamblia）是一种单细胞的原生生物，具有两个阶段的生命周期。贾第鞭毛虫病是由于摄入了囊状的寄生虫，然后在十二指肠中排出成滋养体。滋养体形式具有高度特化的微管细胞骨架（八个鞭毛、“中间体”和“腹盘”），其允许寄生虫逃避宿主肠道中的蠕动。贾第虫感染是寄生虫直接附着在肠上皮上的结果;从上皮层的粘膜分泌物中获得营养。附着的机制尚未完全了解，但最近的证据表明，寄生虫使用腹盘构象变化产生的吸力。腹盘由一个逆时针方向排列的微管，起源于电子致密带直接前面的尾部和后侧鞭毛基体。微管的腹面与质膜相连。在每个微管的背侧是通过交联剂连接到相邻微带的微载体。以前的研究贾第鞭毛虫细胞骨架的重点是了解基本的光盘结构，使用低分辨率的技术，如光学显微镜，化学固定塑料包埋样品，和负染色。在我们的研究中，我们正在使用冷冻电子断层扫描分离洗涤剂提取的细胞骨架，以确定腹盘的各个组成部分之间的结构-功能关系。我们已经使用我们的程序PEET平均腹盘的微管。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Giardia intestinalis (also known as Giardia lamblia) is a unicellular, flagellated protist with a two-stage lifecycle. Giardiasis is caused by ingestion of the cyst form of the parasite which then excysts in the duodenum into the trophozoite form. The trophozoite form has a highly specialized microtubule cytoskeleton (eight flagella, the "median body" and the "ventral disc"), which permits the parasite to evade peristaltic movement in the host's intestine. Infection with Giardia is the results of parasite attachment directly to the intestinal epithelium; deriving nutrients from the mucosal secretions of the epithelial layer. The mechanism of attachment is not fully understood, but recent evidence suggests the parasite uses suction created by conformational changes of the ventral disc. The ventral disc consists of a counterclockwise array of microtubules that originate from electron dense bands directly anterior to the caudal and posterior-lateral flagellar basal bodies. The ventral surface of the microtubules is attached to the plasma membrane. On the dorsal side of each microtubule is a microribbon that is connected to neighbor microribbons by cross-linkers. Previous studies of the Giardia cytoskeleton have focused on understanding the basic disc structure using low-resolution techniques such as light microscopy, chemically fixed plastic embedded samples, and negative stain. In our study, we are using cryo-electron tomography of isolated detergent-extracted cytoskeletons to determine the structural-functional relationships between the various components of the ventral disc. We have used our program PEET to average the microtubules of the ventral disc.