Title |
Minireview] Electron microscopic observations of prokaryotic surface appendages |
Author |
Ki Woo Kim1,2* |
Address |
1School of Ecology and Environmental System, Kyungpook National University, Sangju 37224, Republic of Korea, 2Tree Diagnostic Center, Kyungpook National University, Sangju 37224, Republic of Korea |
Bibliography |
Journal of Microbiology, 55(12),919–926, 2017,
|
DOI |
10.1007/s12275-017-7369-4
|
Key Words |
appendages, archaea, bacteria, extracellular filaments |
Abstract |
Prokaryotic microbes possess a variety of appendages on their
cell surfaces. The most commonly known surface appendages
of bacteria include flagella, pili, curli, and spinae. Although
archaea have archaella (archaeal flagella) and various types
of pili that resemble those in bacteria, cannulae, and hami
are unique to archaea. Typically involved in cell motility, flagella,
the thickest appendages, are 20–26 nm and 10–14 nm
wide in bacteria and archaea, respectively. Bacterial and archaeal
pili are distinguished by their thin, short, hair-like
structures. Curli appear as coiled and aggregative thin fibers,
whereas spinae are tubular structures 50–70 nm in diameter
in bacteria. Cannulae are characterized by ~25 nm-wide tubules
that enter periplasmic spaces and connect neighboring
archaeal cells. Hami are 1–3 μm in length and similar to
barbed grappling hooks for attachment to bacteria. Recent
advances in specimen preparation methods and image processing
techniques have made cryo-transmission electron
microscopy an essential tool for in situ structural analysis of
microbes and their extracellular structures. |