DESCRIPTION OF THE PHYLUM THERMOPLASMOBACTERIA1
| ARCHAEA> EURYARCHAEOTA> THERMOPLASMOBACTERIA |
PHYLUM THERMOPLASMOBACTERIA LINKS
| Thermoplasmobacteria (ther-mo-bak-TE-re-a) is derived from three Greek words that mean “hot” (θερμός -hot), moldable (plasma -πλάσμα) and “little stick” (bakterion -βακτήριον). The name is a reference to their high thermal requirement and variable cell shape. |
| INTRODUCTION TO THE THERMOPLASMOBACTERIA The thermoacidophils are quite distinctive as a group. They are unicellular but lack cell walls, giving them the appearance of microbial amebae (Figures 1and 2). Most have been found in association with hot (36-85C), sulfur-rich acidic conditions that occur in coal mine tailings. Obviously, they must occur in widely-scattered environments with the same characteristics across the globe (and deep underground?). Thermoacidophils have histones (text with tooltip) Histones are particular basic proteins associated with DNA in almost all eukaryotes and one or a few prokaryotes (e.g. <em>Thermoplasma</em>). associated with the bacterial chromosome which may be the smallest of all the free-living bacteria. The cell membrane contains a lipopolysaccharide and glycoproteins (but no sterols) which allow it to be stable in extremely acidic (pH 1-3) environments. Margulis and Schwartz (1998) lump all the thermoacidophils together into a taxon called Crenarchaeota, which we treat as a kingdom. However, Garrity et al. (2001 and 2003) place these organisms in a class Thermoplasmata within their phylum Euryarchaeota. We have followed the relative placement of Garrity et al. (2001) and moved them into the Kingdom Euryarchaeota together with the methanogens and extreme halophiles. We separated Thermoplasma and its relatives from other thermophiles (text with tooltip) Thermophiles are organisms (usually bacteria) that have thermal optima of 45C or higher. because they are only mildly thermophilic, they do not contain sterols in their membranes, they lack a cell wall, and they do contain histones in association with their chromosome. |
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| FIGURE 1. TEM micrograph of Thermoplasma. Image from http://www.biochem.mpg.de/baumeister/genome/home.html | FIGURE 2. SEM micrograph of Thermoplasma that was fixed in an aqueous medium showing the amoeboid nature of the cell. Image from MicrobeWiki, hosted by Kenyon College |
FIGURE 2. The relationships between the Thermoplasmobacteria (in shaded box) relative to other taxa in the Archaea.
C = CRENARCHAEOTA
E = EURYARCHAEOTA
Eu = EURYTHERMEA CLADE
Ne = NEOBACTERIA
| 1. This name is of our invention and refers to taxa that are Euryarchaeota, mildly thermophilic, lack cell walls, have no sterols in their membranes, and have histones associated with the chromosome. |
| FURTHER READING: DISCOVERY OF THE DOMAINS OF LIFE |
| LITERATURE CITED Black, J. G. 2002. Microbiology, Principles and Explorations. 5th ed. John Wiley and Sons, Inc. New York. Gao, B. and R. S. Gupta. 2007. Phylogenetic analysis of proteins that are distinctive of Archaea and its main subgroups and the origin of methanogenesis. BMC Genomics. 8:86. http://www.biomedcentral.com/1471-2164/8/86. Garrity, G. M., M. Winters, and D. Searles. 2001. Bergey’s manual of systematic bacteriology. 2nd ed. Springer-Verlag. New York. Garrity, G. M., J. A. Bell, and T. G. Lilburn. 2003. Taxonomic Outline of the Prokaryotes. Bergey’s Manual of Systematic Bacteriology. 2nd edition. Release 4.0. Springer-Verlag. New York. pp. 1-397. Margulis, L. and K. Schwartz. 1988. Five kingdoms, an illustrated guide to the phyla of life on earth. 2nd Edition. W. H. Freeman and Co. New York. Margulis, L. and K. Schwartz. 1998. Five kingdoms, an illustrated guide to the phyla of life on earth. 3rd Edition. W. H. Freeman and Co. New York. Woese, C. R. and G. E. Fox. 1977. Phylogenetic structure of the prokaryotic domain: the primary kingdoms. Proceedings of the National Academy of Sciences USA. 74:5088-5090. Woese, C. R., O. Kandler, and M. L. Wheelis. 1990. Towards a natural system of organisms: Proposal for the domains Archaea, Bacteria, and Eucarya. Proc. Natl. Acad. Sci. USA. 87: 4576-4579. |
| By Jack R. Holt. Last revised: 02/05/2013 |
