Biomedical Engineering Reference
In-Depth Information
6.4.1 Ultrastructure of the Attachment Organelle
Although the structural features of this organelle were originally found in
the early 1970s [75, 76, 77, 73], detailed study of the structure has not been
well-focused. Recently, some EM study on the structure, including electron
cryotomography (ECT), has achieved some progress [78, 79, 71, 80, 81]. The
structure of the attachment organelle is apparently composed of five parts
(see Figure 6.17): i) the surface structure (nap), ii) segmented paired plates
(rod core), iii) the distal end of the rod (terminal button), iv) the proximal
end of the rod (bowl or wheel), and v) the translucent area.
Figure 6.17.
Architecture of attachment organelle of
M. pneumoniae
. The struc-
tures can be divided into five parts. Each part has been suggested to include the
cytadherence proteins.
Surface Structure (i)
Negative-staining EM revealed a surface structure, called a “nap”, at the tip
[82, 4, 83]. Similar structures can also be found on other gliding species of
the
M. pneumoniae
group, including
M. genitalium, M. pulmonis
,and
M.
gallisepticum
. EM has also been used to demonstrate filamentous elements
between
M. pneumoniae
and the host tissue to which it is bound, but the
relationship between this structure and the nap is unknown [72, 73]. Recent
studies using ECT also revealed clustering of membrane proteins on the sur-
face of the attachment organelle [79, 81]. The units are about 16nm in height,
composed of a proximal stalk part about 10nm in length, and a distal globular
