Classification of Bacteria 

The Bergey’s Manual of Determinative Bacteriology published by Williams and  Wilkins Co. Baltimore, U.S.A. (1974), is the international standard for bacterial taxonomy. It deals with the classification of bacteria (19 parts) and contains descriptions of all species known at the time of its publication. 

Bergey’s manual was revised between 1984 and 1989 and appeared in four volumes with a new name Bergey’s Manual of Systematic Bacteriology. In these four volumes, bacteria have been classified into 33 sections based on morphological and biochemical characteristics.  Bacterial groups are divided into four volumes. 

  • Gram-negative bacteria (1984) of general, medical, and industrial importance. 
  • Gram-positive bacteria (1986) other than actinomycetes. 
  • Gram-negative bacteria (1989) with distinctive properties, cyanobacteria, and archaeobacteria.
  • Actinomycetes (1989) as Gram-positive filamentous bacteria. 

The Bergey’s Manual of Systematic Bacteriology places all bacteria in the Kingdom  Procaryotae which in turn is divided into four divisions which are as follows: 

Kingdom Procaryotae 

Division I: Gracilicutes (Thin skin): Prokaryotes with a complex cell wall structure characteristic of Gram-negative bacteria (e.g. non-photosynthetic bacteria). 

Division II: Firmicutes (Strong skin): Prokaryotes with a cell wall structure characteristic of Gram-positive bacteria (e.g. rods, cocci, actinomycetes). 

Division III: Tenericutes (Soft or tender skin): Prokaryotes that lack a cell wall  (e.g. mycoplasma). 

Division IV: Mendosicutes (Skin with faults): Prokaryotes with unusual cell walls  (e.g. archaeobacteria).

All bacteria are classified as kingdom, division, class, order, family, tribe, genus, section,  series, species, and individual. All microorganisms have a double name, usually from Latin or  Greek stems. The name consists of the genus to which the organism belongs and a species modifier that further describes the genus name. Hence this system is called the binomial system e.g. Escherichia coli, Corynebacterium diphtheriae, etc.

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