bacterial cellular, bacterial cell, nucleoid, ribosomes, storage granules, endospore

True  bacteria (which include all microorganisms that infect man) are members of one kingdom (the eubacteria, microorganisms). In supplement, a group of microorganisms often found in extreme environments form a second kingdom (archaebacteria, Archaea). Morphologically, the two kingdoms of organisms appear similar, specifically in the absence of a nucleus, and thus are classified together as prokaryotes. However, they have major biochemical differences. Most archaea live in circumstances such as hot sulfur springs where they knowledge temperatures as high as eighty degrees C and a pH of two. These are called thermoacidophiles. Others live in methane-containing (methanogens) or high salt (extreme halophiles) circumstances. Archaea Based on DNA sequence similarities, it appears that the archaea and eukaryotes diverged from the eubacteria before they diverged from each other (figure 1a) and in some ways, archaea are biochemically more like eukaryotes than they are the eubacteria. For example, the RNA polymerase of archaea is as complex, in terms of variety of subunits, as the eukaryote atomic polymerases and there is appreciable amino acid homology with some of the eukaryotic subunits. Gene promoter structure in archaea is also more similar to that of eukaryotes than eubacteria, although, like the eubacteria, archaea have operons and transcribe these to polycistronic mRNA. Similarity also exists between the protein functionality factors of archaea and eukaryotes recommending that the overall protein synthesis components of eukaryotes and archaea may be similar. The 16S rRNAs of the eubacteria and the archaea are quite distinctive in sequence. Eubacteria (with the exclusion of the genera Mycoplasma and Chlamydia) possess peptidoglycan (synonyms: murein, mucopeptide, cell wall skeleton). Peptidoglycan, contains a special sugar, muramic acid, not found elsewhere in nature. Archaebacteria contain a pseudomurein that is different in structure from eubacterial murein. In view of the increasing number of resemblances between the archaea and the eukaryotes, the term archaebacteria is no longer used. All other cellular forms of life (consisting of plants, animals, and fungi) are referred to as eukaryotes. Users of the Archaea are not people pathogens and will not be mentioned further.

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