At an EMBO workshop in Copenhagen in 2006 on 'Cell cycle and cytoskeletal elements in bacteria,' I was almost unable to stay put in my seat during one presentation: Grant Jensen showed the 3D-montage of cryoET images of magnetosomes in Magnetospirillum magnetotacticum. It was a visual journey into and through the interior of a cell, and entirely based on the results described in their paper (Figure 1, and Frontispiece). Admittedly, I was never particularly impressed by the movie Fantastic Voyage, but these here weren't stunts, trick shots or CGI animations, unavailable in 1966. These were real data! Processed with computationally intensive algorithms, notwithstanding. Perhaps you can relate to my enthusiasm after you view the 34‑second video, it is still available on Youtube.
That was in 2006, and Grant Jensen was keen to point out that better resolution and contrast were not yet possible, and, almost as an excuse, stated that electron-dense magnetosomes were a particularly easy study object. Today, cryogenic electron microscopy (cryo-EM) is a burgeoning field involving many labs (not gobbling up as much research money as the Large Hadron Collider (LHC) but still...) Cryo-EM and, more specifically, electron cryotomography (cryoET) with subtomographic averaging achieve resolutions in the range of a few Ångström (1 Å=0.1 nm) that were previously reserved for protein crystallographers. And crystallographers and microscopists "meet" successfully in this realm of near-atomic resolution: Xiang et al. (2021), for example, virtually "carved-out stencils" from crystal data in the PDB collection to unmistakably pinpoint ribosomes including their orientation in electron cryotomograms of E. coli cells (see here in STC.)
As a technique, cryoET was − and still is − instrumental in elucidating the fine structure of membrane‑bound macromolecular protein complexes like flagellar motors or the F pilus-associated platforms for conjugation (see here in STC.) As you may know, crystallographers regularly tore their hair out when it came to membrane-bound protein complexes. But CryoET could do even more, visualizing structures that other imaging techniques could not and thus did not find. I am talking about the 'chemosensory arrays' that were discovered and thoroughly studied by Ariane Briegel and co-workers in the Jensen lab (and now in her lab at Leiden University, NL.) Briefly, these arrays represent the sophisticated arrangement of cellular receptors for extracellular signals that are, via a phosphorelay, transmitted to the flagellar motor to trigger, or un-trigger, flagellar rotation. Structure meets function, you might say. Figure 2 shows a chemosensory array of B. burgdorferi in side view, you can see the top-view of E. coli and Treponema arrays here. (An aside. Certainly not in 2006, but now I tend to see a membrane-attached chemosensory array apical to the cell tip on the right at 00:04 sec in the M. magnetotacticum video.)
Now the Jensen lab have summarized and structured their work − and that of their numerous collaborators − of the last fifteen-or-so years in a milestone publication, The Atlas of Bacterial & Archaeal Cell Structure. As the authors say: "The book addresses a fundamental gap in existing textbooks, namely, what bacterial and archaeal cells look like" at near-atomic resolution, "and how the macromolecular structures they contain give rise to their diverse and complex functions." It does not take much to predict that this atlas will be to microbiologists what Gray's Anatomy is to physicians, and a welcome upgrade of The Cell by D.W. Fawcett (2nd. Ed.,1981), the standard work for the electron microscopy of cells, mainly eukaryotic cells.
The atlas is explicitly meant as study material for students and teachers as "the interactive, multimedia resource features real data from more than 150 cells belonging to approximately 70 different species, imaged by cutting-edge cryogenic electron microscopy (cryo-EM). Complementary animations show the cellular machinery in action." I encourage STC readers to dive into the atlas right away by clicking cellstructureatlas.org. This is possible without prior registration and at no cost, as the Jensen lab has published the atlas, hosted by the Caltech Library, under the Creative Commons CC BY-NC 4.0 license.