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DOMAIN EUBACTERIA

The Eubacteria is a prokaryotic domain of life with a set of characters that unite its extraordinarily diverse taxa.  Unlike the Archaea, the Eubacteria have been known and studied for more than 150 years.  This is because all known bacterial pathogens are Eubacteria (I reserve the use of the term bacteria as a descriptive term that is a synonym of prokaryote).  Also, some of them like Lactobacillus are otherwise economically important.  Perhaps more importantly, many of them inhabit environments that are easily studied and sampled.   The Eubacteria differ from the Archaea in the form and structure of their ribosomes, the type and linkage of their lipids, the structure of their cell covering, and the type of RNA polymerase (Margulis and Schwartz 1998).  Traditionally, the Eubacteria have been separated into the Gram positive and Gram negative groups, based upon a standard stain technique.  As it turns out, the way a cell stains is related to the type and structure of the cell wall.  Gram positive cells have a single membrane with a murien or peptidoglycan wall to the outside of the single membrane.  Gram negative cells have an inner membrane and an outer membrane with a murein layer sandwiched between them.  The system of Margulis and Schwartz (1998) is based on the fundamental separation of gram positive and gram negative cells (called Firmicutes and Gracilicutes, respectively).  Phylogenies based on small subunit r RNA, however, show that the eubacteria are marked by 10 or 11 deep clades that I interpret as kingdoms.  This could just be the tip of the iceberg with respect to their true diversity.  Garrity et al. (2001) separate the Eubacteria (a group that they call "Bacteria") into 23 groups.  Also, the problems of lateral gene transfer further blur the distinctions of the groups.  I present a tentative system for the Eubacteria with 9 kingdoms (see below).  This system is based largely on Margulis and Schwartz (1998), with modifications from Garrity et al. (2001, 2003, and 2005), Tudge (2000), and Black (2002).   (View a 16s rRNA phylogenetic tree based on data from Woese).

A simple taxonomy of the Domain Eubacteria.

REFERENCES.

This page is maintained by Jack R. Holt.  Last revised: 04/22/08.