Identification & Classification Systems
1-Numerical Taxonomy
Numerical taxonomy (also called computer taxonomy, phenetics, or
taxometrics) became widely used in the 1960s. Numerical classification
schemes use a large number (frequently 100 or more) of unweighted
taxonomically useful characteristics.
2-Phylogenetic Classifications:
Toward an Understanding of Evolutionary Relationships among
Bacteria Phylogenetic classifications are measures of the genetic
divergence of different phyla (biologic divisions). Close phylogenetic
relatedness of two organisms implies that they share a recent ancestor,
The formal ranks used in the taxonomy of bacteria are listed in Table 1.
Table 1. Taxonomic Ranks.
Formal Rank
Example
Kingdom
Prokaryotae
Division
Gracilicutes
Class
Scotobacteria
Order
Eubacteriales
Family Enterobacteriaceae
Genus
Escherichia
Species
coli
3-Bergey's Manual of Systematic Bacteriology
Bergey's Manual of Systematic Bacteriology. First published in 1923,
the Manual is an effort to classify known bacteria and to make this
information accessible in the form of a key. A companion volume,
Bergey's Manual of Determinative Bacteriology, serves as an aid in the
identification of those bacteria that have been described and cultured.
Description of the Major Categories & Groups of Bacteria
There are two different groups of prokaryotic organisms: eubacteria
and archaebacteria. Eubacteria contain the more common bacteria,
Archaebacteria do not produce peptidoglycan, a major difference between
them and typical eubacteria. They also differ from eubacteria in that they
live in extreme environments (eg, high temperature, high salt, or low pH)
and carry out unusual metabolic reactions, such as the formation of
methane.
Eubacteria Lacking Cell Walls
These are microorganisms that lack cell walls (commonly called
mycoplasmas and comprising the class Mollicutes) and do not synthesize
the precursors of peptidoglycan. They are enclosed by a unit membrane,
the plasma membrane They resemble the L forms that can be generated
from many species of bacteria (notably gram-positive eubacteria); unlike
L forms, however, mycoplasmas never revert to the walled state, and
there are no antigenic relationships between mycoplasmas and eubacterial
L forms.