Bergey’s Manual® of Systematic Bacteriology

pp 471-566

Phylum XV. Spirochaetes Garrity and Holt 2001

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Spirochetes are Gram-stain-negative, helical or spiral-shaped, motile cells that can flex, rotate and translate through liquid and semisolid environments. Most spirochetes possess a cellular ultrastructure unique to bacteria in that they have internal organelles of motility, namely periplasmic flagella. Consequently, the spirochetes are one of the few bacterial phyla whose phenotypic characteristics, e.g., cell morphology, reflect its phylogenetic relationships as based on 16S rRNA gene sequence comparisons (Garrity and Holt, 2001), forming a distinct line of evolutionary descent among the bacteria (Garrity et al., 2005).