Note on Gra1 - bacterial groups; these techniques may...

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Note on Gram-positive bacteria and bacteria taxonomy: One hears a lot about "gram positive" and "gram negative" bacteria. The above tree should illustrate that gram-positive bacteria represent a fairly small proportion the extant bacteria. Gram positive refers to the cell-wall phenotype of these bacteria, the presence of which can be recognized by a "Gram stain" named for the person (Christian Gram) who developed the stain. Mycobacterium tuberculosis (TB) and Mycoplasma pneumoniae (walking pneumonia) are both gram-positive bacteria. Microbiologists have many techniques for characterizing
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Unformatted text preview: bacterial groups; these techniques may distinguish bacterial groups which are phylogenetically distinct, but the techniques are not based on phylogeny (and are therefore taxonomic). Other techniques include relative sensitivities to different antibiotics, antibodies, or more recently DNA sequence analysis (which are phylogenetically based). Taxonomy organizes "things" by convenient and at times unreliable markers (e.g. does the insect have yellow or red wings?). Phylogeny organizes organisms based on their evolutionary relatedness and hence directly or indirectly by genetic markers....
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