Introduction to the Spirochetes
The order Spirochaetales consists of helically shaped bacteria with a distinguishing anatomy and locomotion. Although these bacteria are morphologically similar, their physiology and habitats are heterogeneous. The order Spirochaetales contains obligate a
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Introduction to the Spirochetes RUSSELL C. JOHNSON
The order Spirochaetales consists of helically shaped bacteria with a distinguishing anatomy and locomotion. Although these bacteria are morphologically similar, their physiology and habitats are heterogeneous. The order Spirochaetales contains obligate anaerobes, facultative anaerobes, and obligate aerobes. Substrate requirements range from fatty acids to amino acids. Habitats are extremely diverse, and range from mud to the convoluted tubules of the mammalian kidney. In the eighth edition of Bergey's Manual of Determinative Bacteriology, five genera of spirochetes, Spirochaeta, Cristispira, Treponema, Borrelia, and Leptospira, are recognized as members of the order Spirochaetales. Three additional genera, Pillotina, Hollandina, and Diplocalyx, have been proposed as members of this order (see this Handbook, Chapter 47). In addition to the above spirochetes, there are many that have not been fully classified, such as the brine shrimp spirochete. This spirochete infects the brine shrimp, Artemia salina, and is found in both extracellular and intracellular locations (1Yson, 1974a). Its presence is associated with lesions in the renal tubules of the brine shrimp (Tyson, 1974b). The genera Cristispira, Pillotina, Hollandina, and Diplocalyx represent large spirochetes that have cell diameters of 0.4-10 ILm; their cell lengths may be greater than 100 ILm. The Cristispira species are commensal in mollusks. The Pillotina, Hollandina, and Diplocalyx species are commensal in the hindgut of termites, where they are usually associated with flagellates. Spirochetes in the genera Treponema, Borrelia, and Leptospira are capable of causing disease in humans and animals. These spirochetes have cell diameters of 0.09-0.5 ILm and an average length of 6- 7 ILm. The genus Spirochaeta consists of free-living spirochetes which are present in mud and polluted waters, and range in size from 0.2 X 5 ILm to 0.75 x 500 ILm. All spirochetes have the following structural features: (0 a helically shaped protoplasmic cylinder (PC), which consists of the cell wall, cytoplasmic membrane, and the enclosed cytoplasmic components; (ii) surrounding the PC is a multilayered outer envelope (OE) or outer sheath; (iii) located between the OE and PC are the flagella (axial filaments or M. P. Starr et al. (eds.), The Prokaryotes © Springer-Verlag Berlin Heidelberg 1981
axial fibrils). The flagella are attached subterminally at opposite ends of the PC with the free ends extended toward the center of the cell. The OE of the large spirochetes is somewhat more complex than those of the other spirochetes (see this Handbook, Chapter 47). Pillotina species have an OE that has three electron-dense and two interposed, electron-transparent layers. The outer two electron-dense layers take part in the protruding crenulations that occur on the surface of the cell. The third electron-dense layer is not part of the crenulations. A fuzzy, amorphous layer covers the OE of Hollandina and crenulations are not present. The ou
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