DIVERSITY OF LIFE

DESCRIPTION OF THE PHYLUM EPSILONPROTEOBACTERIA (STACKENBRANDT ET AL. 1988)

EUBACTERIA>PROTEOBACTERIAE>EPSILONPROTEOBACTERIA

Epsilonproteobacteria (ep-si-lon-PRO-te-o-bak-TE-re-uh) is derived from two Greek roots and a Greek letter meaning "epsilon" (ε) "changeable" (proteakos -πρωτεϊκός) "little stick" (bakterion -βακτήριον).  The name is in reference to Proteus, the name of a Greek sea god who could change his shape (Stackebrandt et al. 1988).

 

INTRODUCTION TO THE EPSILONPROTEOBACTERIA

Epsilonproteobacteria are unicellular Gram negative rods or spirals, with single, unsheathed polar flagella.  Organisms in this group are poorly understood, but they seem to constitute major microbial constituents of sulfur-rich hydrothermal vent and microbial mat communities (Figure 1).  In addition, some taxa like Helicobacter (Figure 2) seem to be opportunistic pathogens that live as "quiet" infections in places like the gums and stomach, where under some circumstances, can cause periodontal disease and stomach ulcers, respectively.  A symbiotic relationship has been reported between a snail of hydrothermal vents and a member of this phylum.

Stackebrandt et al. (1988), using 16S rRNA sequences, defined a seemingly unrelated group of eubacteria as Proteobacteria, the purple bacteria, which they defined as a class that they called Proteobacteria.  Within that group, they defined five separate lines, each defined by a Greek letter: α, β, γ, δ, ε.  The second edition of Bergey's Manual of Systematic Bacteriology (Garrity et al. 2003) adopted Proteobacteria, but raised it to phylum level with each of the five groups becoming classes.  In order to bring the prokaryotes into line with kingdom-level divisions in the eukaryotes, we felt that it was necessary to raise the Proteobacteria to kingdom-level status with each of the five groups also raised to the level of phylum.

The Epsilonproteobacteria is perhaps the least well known of the five phyla.  Garrity et al. (2003) has only a single order (Campylobacteriales).  Campbell et al. (2006) added Nautiliales and four other unnamed orders.  Clearly, the structure of this phylum is more diverse than its current structure would indicate.


FIGURE 1

 

 

FIGURE 3.  Topology of the Proteobacteria with the relationships of the phyla and the single class of the Epsilonproteobacteria (in shaded box).

 


FIGURE 2

FURTHER READING:

DISCOVERY OF THE DOMAINS OF LIFE

DESCRIPTION OF THE DOMAIN ARCHAEA

 

LITERATURE CITED

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By Jack R. Holt.  Last revised: 02/20/2013