An Overview of Procaryotic Cell Structure
Because much of this chapter is devoted to a discussion of individual cell components, a preliminary overview of the procaryotic cell as a whole is in order.
Size, Shape, and Arrangement
One might expect that small, relatively simple organisms like
procaryotes would be uniform in shape and size. Although it is
true that many procaryotes are similar in morphology, there is a
remarkable amount of variation due to differences in genetics
and ecology. (figures 3.1 and 3.2; see also figures 2.8 and 2.15).
Major morphological patterns are described here, and interesting variants are mentioned in the procaryotic survey (see chapters 20–24).
Most commonly encountered bacteria have one of two
shapes. Cocci (s., coccus) are roughly spherical cells. They can
(a)
(c)
(e)
(b)
(d)
Figure 3.1 Representative Bacteria. Stained bacterial cultures as
seen in the light microscope. (a) Staphylococcus aureus. Note the
gram-positive spheres in irregular clusters. Gram stain (1,000).
(b) Enterococcus faecalis. Note the chains of cocci; phase contrast
(200). (c) Bacillus megaterium, a rod-shaped bacterium in chains.
Gram stain (600). (d) Rhodospirillum rubrum. Phase contrast
(500). (e) Vibrio cholerae. Curved rods with polar flagella (1,000)
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