Figure 1. (a) Photograph of a piece of the gunflint chert from the northern shore of Lake Superior, Ontario, Canada. The rock measures about 20 cm along the long axis and the wavey striations of the layers of an ancient ~3000 million-year-old stromatolite can be seen in the middle of the rock. (b) Bright-field light micrograph of a thin section of the gunflint chert showing the mineralized remains of prokaryotic cells. (c) Light micrograph using phase optics of a living modern-day biofilm from a stream in southern Ontario for comparison with (b). These figures were originally supplied by F.G. Ferris, University of Toronto and are reprinted from Beveridge (1988) with permission of the Canadian Journal of Microbiology. Copyright © 1988 NRC Research Press.

Figure 2. Electron micrograph of a thin section of Leptothrix discophera which shows many structural attributes of a bacterial cell. This is a Gram-negative cell and the inner bilayer of the cell envelope is called the plasma membrane which encloses the cytoplasm. Reprinted from Beveridge (1988) with permission of the Canadian Journal of Microbiology. Copyright © 1988 NRC Research Press.

Figure 3. Thin section of a magnetotactic spirillum (a Gram-negative bacterium) which contains a chain of magnetosomes containing small particles of magnetite ( Fe₃O₄). This sample was supplied by D. Bazylinski, University of Iowa.

Figure 4. (a) Thin section of the cyanobacterium Synechococcus GL-24 showing the concentric arrangement of the photosynthetic membranes and the carboxysomes. (b) Thin section of a Chlorobium sp. which is a green sulfur bacterium showing the photosynthetic chlorosomes. Both (a) and (b) were provided by S. Douglas, University of Guelph and reprinted from Schultze-Lam S et al. (1992) Journal of Bacteriology 174: 7971–7981, with permission from the American Society for Microbiology.

Figure 5. Electron micrograph of a negatively stained Caulobacter sp. showing its unusual shape complete with stalk and holdfast. Reprinted from Beveridge (1988) with permission of the Canadian Journal of Microbiology. Copyright © 1988 NRC Research Press.

Figure 6. Negative stain of the proximal end of a flagellum from Campylobacter fetus subsp. fetus which shows the filament, hook and basal body (L, P and S-M rings).

Figure 7. Thin section of a Bacillus megaterium endospore.