Page:Bergey's manual of determinative bacteriology.djvu/914

 ORDER IX. SPIROCHAETALES BUCHANAN, 1918.

Spi.ro.chae. tales. M.L. fem.n. Spirochaeta type genus of the order; -ales ending to denote an order; M.L. fem.pl.n. Spirochaetales the Spirochaeta order.

Slender, flexuous bodies, 6 to 500 microns in length, in the form of spirals with at least one complete turn. Some forms may show an axial filament, a lateral crista, or ridge, or transverse striations; otherwise there is no significant protoplasmic pattern. Smaller forms may have a lower refractive index than that of true bacteria, and therefore they can be seen only with dark-field illumination. Some forms take aniline dyes with diflficulty; Giemsa's stain is uniformly successful. Granules are formed in some species which are found in vector hosts. All forms are motile. In the true bacteria, motility is effected by flagella endowed with a lashing movement; however, no such structures exist among the spirochetes. Terminal projections, whether derived from the periplast or from the axial filament, may assist in the movements, and it is possible that the crista has a similar function, although neither of these structures can explain the violent motion of the spirochetes. This motility consists of a rapid whirling or spinning about the long axis, which activity drives the organism forward or backward, there being no anteroposterior polarity. In addition the spirochetes make violent, lashing movements, curling and uncurling their spirals. Multiplication is by transverse fission, no sexual cycle being known. Free-living, saprophytic and parasitic forms.

I. Spirals 30 to 500 microns in length, possessing definite protoplasmic structures. Family I. Spirochaetaceae, p. 892. II. Spirals 4 to 16 microns in length, possessing no obvious protoplasmic structure. Family II. Treponemataceae, p. 896.

Spi.ro. chae.ta'ce.ae. M.L. fem.n. Spirochaeta type genus of the family; -aceae ending to denote a family; M.L. fem.pl.n. Spirochaetaceae the Spirochaeta family.

Coarse, spiral organisms, 30 to 500 microns in length, possessing definite protoplasmic structures. Found in stagnant, fresh or salt water and in the intestinal tracts of bivalve molluscs (Lamellibranchiata).