Universidade do Grande Rio (UNIGRANRIO), Rio de Janeiro, Duquxe de Caxias, Rio de Janeiro, Brazil.
Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil.
J Eukaryot Microbiol. 2022 Nov;69(6):e12893. doi: 10.1111/jeu.12893. Epub 2022 Mar 2.
Giardia intestinalis has unique characteristics, even in the absence of certain organelles. For instance, Golgi and mitochondria are not found. On the other hand, there is a network of peripheral vacuoles (PVs) and mitosomes. The endoplasmic reticulum (ER), nuclear membrane, peroxisomes, and lipid bodies are present. The peripheral vacuole system seems to play several simultaneous roles. It is involved in the endocytic activity of the trophozoite but also has characteristics of early and late endosomes and even lysosomes, establishing a connection with the ER. Some of the PVs contain small vesicles, acting as multivesicular bodies, including the release of exosomes. The mitosomes are surrounded by two membranes, divide during mitosis, and are distributed throughout the cell. They do not contain DNA, enzymes involved in the citric acid cycle, respiratory chain, or ATP synthesis. However, they contain the iron-sulfur complex and transporters as TOM and TIM. Some mitosomes are linked to flagellar axonemes through a fibrillar connection. During encystation, two types of larger cytoplasmic vesicles appear. One originating from the ER contains the cyst wall proteins. Another contains carbohydrates. Both migrate to the cell periphery and fuse with plasma membrane secreting their contents to give rise to the cell wall.
肠道贾第虫具有独特的特征，即使在缺乏某些细胞器的情况下也是如此。例如，没有发现高尔基体和线粒体。另一方面，存在一个外周液泡（PVs）和线粒体体网络。内质网（ER）、核膜、过氧化物酶体和脂滴都存在。外周液泡系统似乎同时发挥多种作用。它参与滋养体的内吞作用，但也具有早期和晚期内体的特征，甚至是溶酶体的特征，并与 ER 建立联系。一些 PVs 包含小泡，充当多泡体，包括外泌体的释放。线粒体体被两层膜包围，在有丝分裂过程中分裂，并分布在整个细胞中。它们不含有 DNA、柠檬酸循环、呼吸链或 ATP 合成中涉及的酶。然而，它们含有铁硫复合物和转运蛋白，如 TOM 和 TIM。一些线粒体体通过纤维状连接与鞭毛轴丝相连。在包囊形成过程中，会出现两种类型的较大细胞质囊泡。一种源自 ER，包含囊壁蛋白。另一种含有碳水化合物。两者都迁移到细胞外周，并与质膜融合，将其内容物释放出来，形成细胞壁。
