Taxonomy and Phylogeny

Modern taxonomy (classification) of bacteria is based on phylogeny (evolutionary history) and the domain Bacteria are divided into 24 phyla (major lines of descent). The phylogeny of organisms can be deduced from molecular sequences. Sequence analysis of the 16S rRNA genes has proved to be extremely useful for establishing bacterial phylogeny and evolutionary relations can be represented by phylogenetic trees. Bacteria of the genus Brachyspira belong to the phylum Spirochaetes (trivial name spirochetes), which consists of one class (Spirochaetes) only. This class consists of one order (Spirochaetales), which is divided into three families as shown in Table 1.

These families are further subdivided into genera (Table 1). The phylogenetic relations within the spirochetes are shown in Fig. 1. Seven species have been officially described within the genus Brachyspira, but reports on some other species without standing in nomenclature can also be found in the literature (see Table 2).

The phylogenetic relations between some representative taxa within the genus Brachyspira are shown in Fig. 2. (under construction). A larger number of strains are included in Fig. 3 (under construction) to illustrate the biodiversity within genus Brachyspira.

• Fig. 1. Phylogeny of the order Spirochaetales.
• Table 1. Taxonomy of the order Spirochaetales.
• Table 2. Species of the genus Brachyspira.