ABSTRACT
Members of the order Spirochaetales are slender, flexuous, unicellular, helically coiled organisms 5 to 500 μm long and 0.1 to 3 μm wide; they have one or more complete turns in the helix. The organisms are Gram-negative, but are best observed by dark-field microscopy or phase-contrast microscopy. They are motile, with a rapid whirling about the long axis of the cell, flection, and movement in a corkscrew or serpentine fashion. Spirochetes consist of an outer cell envelope and an inner protoplasmic cylinder. Between the cell envelope and the protoplasmic cylinder are axial fibrils that are inserted into the cylinder wall at each end of the cell and extend along the cell towards the opposite end of the cell. Bizarre forms of spirochetes may be seen. Bullae, for example, are swellings of the cell envelope. In old cultures, spirochetes may coil up, forming spheres or coccoid forms that may break up into granules. The coccoid forms and granules are also found in cultures treated with chemicals such as penicillin.1 Spirochetes are both aerobic and anaerobic. They are found free-living or saprophitic in nature or are parasitic. Some species are pathogenic for man and animals.
