The Genus Brachyspira

Abstract

Brachyspira is the sole genus assigned to the pro- posed Family “Brachyspiraceae” in the Order Spirochaetales (Paster and Dewhirst, 2000). The Order Spirochaetales contains all spirochetes. The spirochetes represent a monophyletic lin- eage and a major early branch in eubacterial evolution (Paster et al., 1984; Paster and Dew- hirst, 2000). Brachyspira cells share with other spirochetes several properties that distinguish them from other bacteria. These include a helical cell shape (Fig. 1) and a cell ultrastructure that features internal periplasmic flagella, 16S rDNA sequences with spirochete signature nucleotide bases, and a natural resistance to the antibiotic rifampin (Paster and Dewhirst, 1997; Paster and Dewhirst, 2000). Brachyspira species are readily differentiated from other spirochete genera based on comparisons of their 16S rDNA sequences (Paster et al., 1991; Paster and Dew- hirst, 1997).