THE EUBACTERIA
| SYSTEMATIC BIOLOGY |
THE EUBACTERIA |
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| PHYLUM BETAPROTEOBACTERIA | |||||
INTRODUCTION TO THE BETAPROTEOBACTERIA
The Betaproteobacteria are chemoautotrophic bacteria are quite variable in form and grow on the energy supplied by small inorganic compounds, which they fix into the production of all necessary organic compounds. Thus, they convert species of inorganic elements from one form to another and come in three general forms as manifest by their metabolic requirements: nitrogen, sulfur, and small organic molecules (e.g. methanol). Others require and oxidize complex organics. At least three groups include nitrogen fixers, and some of the Burkerholderales can enter into nodule-forming symbioses with plants. Thus, the taxa in this phylum are very important in mediating the cycling of the elements nitrogen, sulfur, and carbon through the ecosystem and biosphere.
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A. Nitrosomonas, organisms that oxidize ammonium to nitrite. |
B. SEM micrograph of Thiobacillus, which use the Calvin Cycle to fix carbon dioxide. They use sulfur compounds, rather than water, as electron donors. |
C. TEM micrograph of Methylobacillus, a motile taxon that utilizes methanol as a carbon source. |
| Images taken from: A: http://web.rollins.edu/~cramirez/Images/nitrobacter.jpg B: http://genome.jgi-psf.org/draft_microbes/images/thide.jpg C: http://genome.jgi-psf.org/finished_microbes/metfl/metfl.home.html |
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SYNOPTIC DESCRIPTION OF THE BETAPROTEOBACTERIA
| The following description comes mainly from Garrity et al. (2003). |
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I. SYNONYMS: β-proteobacteria, nitrogen-fixing bacteria, . II. PHYLUM CHARACTERISTICS: A. Structure Cell Form: Variable; rods, cocci, spirals; and filaments. Cell Wall: Gram-. Motility: Non-motile or motile; some are mobile (move without flagella in contact with a substrate). B. Physiology O2 Tolerance: Aerobes or facultative anaerobes. Substrates: Some obtain their carbon from CO2 and a variety of organic sources. Electron sources are sulfur compounds and hydrogen. Others utilize ammonium and other nitrogen compounds. Most are chemoorganotrophs and chemolithotrophs. Products: They produce a variety of oxidized carbon, nitrogen, and sulfur compounds. C. Other: Very diverse group of bacteria. D. Ecology: Free-living in soils and aquatic sediments; some are nodule-formers. |
SYSTEMATICS OF THE BETAPROTEOBACTERIA
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 Betaproteobacteria seems to be a songle clade; thus, I have a single class within the phylum. The ordinal structure is from Garrity et al. (2003).
HIERARCHICAL CLASSIFICATION OF THE BETAPROTEOBACTERIA
| This is a modification of Garrity et al. (2003). |
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CLASS BETAPROTEOBACTERIAE
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This page is maintained by Jack R. Holt. Last revised: 02/05/2008.
