Parasitology meets cryo-electron tomography – exciting prospects await.

Cryo-electron tomography (cryo-ET) is a cryo-electron microscopy (EM) approach that allows 3D imaging of cellular structures in near-native, frozen-hydrated conditions with molecular resolution. Continued development of technologies, including direct electron detectors, phase plates, and energy filters, has improved the information yield from cellular samples, which is further extended by newly developed workflows for data collection and analyses. Moreover, advanced sample-thinning techniques, such as cryogenic focused ion-beam (cryo-FIB) milling, provide access to parasitic events and structures that were previously inaccessible for cryo-ET. Cryo-ET has therefore become more versatile and capable of transforming our understanding of parasite biology, particularly that of apicomplexans. This review discusses cryo-ET's implementation, its recent contributions, and how it can reveal pathogenesis mechanisms in the near future using apicomplexans as a case study. This review discusses recent advances in cryo-electron tomography (cryo-ET) data collection schemes, imaging technologies, and data processing and analyses such as annotation and subtomogram averaging that have augmented its impact on parasitology. The review illustrates workflows for cryo-ET incorporating additional technologies such as cryogenic focused ion-beam (cryo-FIB) milling that grant cryo-ET access to previously inaccessible biology. The review demonstrates the use of cryogenic correlative light and electron microscopy (cryo-CLEM) and other microscopy techniques to aid in targeted cryo-FIB milling and/or cryo-ET. The review cites studies on apicomplexan biology that demonstrate the current capabilities of cryo-ET. These include cryo-ET structures of apical complex components such as the conoid and the rhoptry secretion system, cytoskeletal elements such as actin and microtubule filaments, and other cellular organelles. [ABSTRACT FROM AUTHOR]