The motile surface structures were ignored or assumed, with good reason, to be cilia or undulipodia (eukaryotic "flagella") until careful study by superb observers (Kirby, 1941; Copeland, 1956) or electron microscopic studies (e.g., Grimstone and Cleveland, 1964) demonstrated otherwise (Fig.
Whereas undulipodia in their kinetids are beneath the eukaryotic plasma membrane, by contrast both ecto-and endosymbiotic spirochetes are covered by their own cell walls (Figs.
3), the kineto-some at the protist cell surface, and the portion of the axoneme illustrate the typical position of standard eukaryotic mature undulipodia at the membrane (pcm).
This favorite habitat of spirochetes between the undulipodia of the dense populations of archaeprotists in termite organic-rich viscous intestinal fluid has been described for years (Bloodgood and Fitzharris, 1976).
The bacteria are attached to at least one distinctive unknown amitochondriate cellulolytic protist covered with undulipodia and likely to be uninucleate, suggesting that it is a hypermastigote class Parabasalia, order Hypermastigida.
(2) The karyomastigont organellar system (a chromosome-containing membrane-bounded nucleus with a proteinaceous connector that attaches to the centriole-kinetosomes at the base of the undulipodia) evolved in response to selection pressures that tended to separate attached spirochetes (eubacteria that became undulipodia) from their sulfidogenic archaebacterial partners (the rest of the cytoplasm).
Complex eukaryotic cells (some as much as 10,000 times the size of a bacterium) can also be characterized as cooperative ventures--obligate federations that may have originated as symbiotic unions (parasitic, predatory or perhaps mutualistic) between ancient prokaryote hosts and what have now become cytoplasmic organelles, particularly the mitochondria, the chloroplasts and, possibly, eukaryotic undulipodia
(cilia) and certain other internal structures that may have evolved from structurallysimilar spirochete ancestors (Margulis 1993).
Complex eukaryotic cells (several thousand times the size of a bacterium on average) can also be characterized as cooperative ventures--obligate federations that may have originated as symbiotic unions (parasitic, predatory or perhaps mutualistic) between ancient prokaryote hosts and what have now become cytoplasmic organelles, particularly the mitochondria, the chloroplasts and, possibly, eukaryotic undulipodia
(cilia) and certain internal structures that may have evolved from structurally similar spirochete ancestors (Margulis, 1993).
They advance by flexing their sensory undulipodia
, but, like garbage trucks, they take in the suitable wood fragments through the hind end.
Briefly, biological work can be broken down into five overlapping but functionally distinct categories: (1) chemical (e.g., the biosynthesis of proteins, nucleic acids, lipids and polysaccharides, or the production of ATP); (2) active transport, such as the energy-dependent `uphill' movement of molecules against a gradient or the `pumping' and excretion of unwanted substances; (3) mechanical, ranging from cell division and muscle contraction to the propulsion provided by flagella and undulipodia
(cilia); (4) electrical, from the transmission of nerve impulses to osmotic activity and firefly illumination; and (5) thermal, including especially homeothermy (see Figure 1).