THE EUBACTERIA
| SYSTEMATIC BIOLOGY |
THE EUBACTERIA |
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| HOME | SYLLABUS | WEEKLY ASSIGNMENTS | J. SYSTEMATIC BIOLOGY | TAXA OF LIFE | |
| KINGDOM CHLOROFLEXAE | |||||
INTRODUCTION TO THE CHLOROFLEXAE AND ITS SINGLE PHYLUM, CHLOROFLEXOBACTERIA
Chloroflexae (klo-ro-FLEX-e) is a standization for this system from the phylum name, Chloroflexi (Garrity and Holt 2001 emend. Hugenholtz and Stackebrandt 2004). It is formed from a common genus, Chloroflexuss, which is formed from a Greek and Latin root meaning green (chloros χλοερός) and bend (flexus). The reference is to the green pigment in a filamentous organism that can bend and glide.
The Chloroflexae is a kingdom with a single phylum, Chloroflexobacteria. The Chloroflexae are filamentous green non-sulfur bacteria that tolerate oxygen and have unique photosynthetic structures and accessory pigments. The carbon fixation pathway is unique with CO2 combining with Acetyl CoA to make hydroxypropionate. They seem to be ubiquitous and have been found in open freshwater and ocean, sediments (marine and freshwater), and soil (Morris et al. 2004), as well as common components of activated sludge in sewage treatment plants (Bjornsson et al. 2002). The filaments look and behave like small Oscillatoria (see the Cyanobacteria) in that they can glide when attached to surfaces.
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A. Chloroflexus |
| Image taken from: http://microscope.mbl.edu/baypaul/microscope/images/t_imgAZ/chloroflexus_msw.jpg |
SYNOPTIC DESCRIPTION OF THE CHLOROFLEXOBACTERIA
| 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: Green nonsulfur phototrophs. II. PHYLUM CHARACTERISTICS A. Structure Cell Form: Filaments, some cells quite large. Cell Wall: Gram-. Motility: Non-motile with gliding filaments.. B. Physiology O2 Tolerance: Tolerant of free oxygen. Substrates: Photoautotrophs with fixation of CO2 and reduction by H2S or H2. Facultative heterotrophs with a variety of small organic compounds as food sources. Products: C. Other: No gas vesicles in cells. Instead, pigmented, photosynthetic vesicles with plant-like carotenoids and chlorosomes (thylakoid-like structures) that contain bacteriochlorophylls. D. Ecology: Grow as mats in aquatic habitats, some tolerant of high temperatures (up to 70C). |
SYSTEMATICS OF THE CHLOROFLEXOBACTERIA
Once grouped with Chlorobia as the Green Non-Sulfur Bacteria, the Chloroflexus group was separated on the basis of its 16S rRNA. I follow the system of Margulis and Schwartz (1998) in which the phylum is designated B-7. At present, the phylum has only five genera that are placed in a single class (CHLOROFLEXI) with a single order (CHLOROFLEXIALES). Bergey's Manual of Systematic Bacteriology, 2nd edition (Garrity et al 2001) treats the taxa that I include in the Chloroflexae as a phylum (B VI. "Chloroflexi") of Bacteria.
HIERARCHICAL CLASSIFICATION OF THE CHLOROFLEXOBACTERIA
| This system comes from that of Margulis and Schwartz (1998) with some modifications based on Garrity et al. (2001 and 2003). |
CLASS CHLOROFLEXI
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This page is maintained by Jack R. Holt. Last revised: 04/22/2008.
