The mitochondrion is crucial for ATP generation by oxidative phosphorylation, among other processes. Cristae are invaginations of the mitochondrial inner membrane that house nearly all the macromolecular complexes that perform oxidative phosphorylation. The unicellular parasite Trypanosoma brucei undergoes during its life cycle extensive remodeling of its single mitochondrion, which reflects major changes in its energy metabolism. While the bloodstream form (BSF) generates ATP exclusively by substrate‐level phosphorylation and has a morphologically highly reduced mitochondrion, the insect‐dwelling procyclic form (PCF) performs oxidative phosphorylation and has an expanded and reticulated organelle. Here, we have performed high‐resolution 3D reconstruction of BSF and PCF mitochondria, with a particular focus on their cristae. By measuring the volumes and surface areas of these structures in complete or nearly complete cells, we have found that mitochondrial cristae are more prominent in BSF than previously thought and their biogenesis seems to be maintained during the cell cycle. Furthermore, PCF cristae exhibit a surprising range of volumes in situ, implying that each crista is acting as an independent bioenergetic unit. Cristae appear to be particularly enriched in the region of the organelle between the nucleus and kinetoplast, the mitochondrial genome, suggesting this part has distinctive properties.

中文翻译：

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布氏锥虫生命周期中线粒体的超微结构变化

线粒体对于氧化磷酸化等过程产生 ATP 至关重要。嵴是线粒体内膜的内陷，几乎容纳了所有进行氧化磷酸化的大分子复合物。单细胞寄生虫 布氏锥虫 在其生命周期中，其单个线粒体经历了广泛的重塑，这反映了其能量代谢的重大变化。血流形式 (BSF) 仅通过底物水平磷酸化产生 ATP，并且线粒体在形态上高度减少，而寄居昆虫的前环形式 (PCF) 进行氧化磷酸化并具有扩展的网状细胞器。在这里，我们对 BSF 和 PCF 线粒体进行了高分辨率 3D 重建，特别关注它们的嵴。通过测量完整或接近完整细胞中这些结构的体积和表面积，我们发现 BSF 中的线粒体嵴比以前认为的更为突出，并且它们的生物发生似乎在细胞周期中得以维持。此外，PCF 嵴在原位表现出惊人的体积范围，这意味着每个嵴都充当独立的生物能单元。嵴似乎在细胞核和动质体（线粒体基因组）之间的细胞器区域特别丰富，表明该部分具有独特的特性。