THE EUBACTERIA
| SYSTEMATIC BIOLOGY |
THE EUBACTERIA |
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| HOME | SYLLABUS | WEEKLY ASSIGNMENTS | J. SYSTEMATIC BIOLOGY | TAXA OF LIFE | |
| PHYLUM EPSILONPROTEOBACTERIA | |||||
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. In addition, some taxa like Helicobacter 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.
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A. Photograph of a microbial mat from White Sulfur Springs, Louisiana. |
B. SEM micrograph of Helicobacter pylori, a causative agent of peptic ulcer. |
| Images taken from: A: http://www.geol.lsu.edu/aengel/epsilon.htm B: http://digestive.niddk.nih.gov/ddiseases/pubs/hpylori/ |
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SYNOPTIC DESCRIPTION OF THE EPSILONPROTEOBACTERIA
| The following description comes mainly from Margulis and Schwartz (1998), Barnes (1984), Brock et al. (1994), and Tudge (2000). |
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I. SYNONYMS: ε-proteobacteria, and helical bacteria. II. PHYLUM CHARACTERISTICS: A. Structure Cell Form: Unicellular spiraled rods. Cell Wall: Gram-. Motility: Motile polar flagella. B. Physiology O2 Tolerance: Anaerobic; microaerophilic. Substrates: Inhabitants of hydrothermal vents and microbial mats are chemolithoautotrophic and use a variety of inorganic compounds as electron sources: H2, formate, fumarate, sulfide, elemental sulfur, thiosulfate, and complex organic compounds. Pathogens and commensals oxidize only amino acids or TCA (Kreb's Cycle) intermediates. Products: Include H2S, NH3, N2, nitrite, nitrous oxide. C. Other: Some are important opportunistic pathogens. D. Ecology: Many are thermophiles associated with geothermal vents. They can be important constituents of microbial mats, and live as commensals/opportunistic pathogens. |
SYSTEMATICS OF THE EPSILONPROTEOBACTERIA
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, I 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. I present the following system with a single class and at least two orders.
HIERARCHICAL CLASSIFICATION OF THE EPSILONPROTEOBACTERIA
Here, I place the organisms into Phylum Epsilonproteobacteria which has a single class (Campylobacteriae). The 2 orders correspond to the named taxa of Campbell et al. (2006). |
CLASS CAMPYLOBACTERIAE
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This page is maintained by Jack R. Holt. Last revised: 02/05/2008.
