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In this article we will discuss about the ten main orders under which bacteria has been classified.
Order I. Pseudomonadales:
It includes some photosynthetic, some chemosynthetic and many heterotrophic bacteria with straight, curved or spiral rods usually with polar flagellation. They are gram-negative and reproduce always by fission. The order includes 7 families.
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Of these the two important ones are:
Family 1. Nitrobacteriaceae:
It includes nitrogen-fixing bacteria and chemosynthetic species which convert ammonia to nitrites or nitrites to nitrates.
Family 2. Pseudomonadaceae:
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It includes common heterotrophic bacteria of soil and water. Some of these cause plant diseases and others fermentation. The important genera are Pseudomonas, Xanthomonas, some Vibrios and Spirilla.
Order II. Chlamydobacteriales:
They form trichomes usually with sheaths and are found in water.
Order III. Hyphomicrobiales:
Cells are ovoid or spherical and reproduce by budding. They are gram-negative and found in water or mud.
Order IV. Eubacteriales:
Includes straight rods or spherical, simple, motile or non-motile, flagellation non-polar and peritrichous, reproduce usually by fission.
The order includes a number of families:
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Family 1. Azotobacteriaceae:
It includes soil forms which are non-symbiotic nitrogen fixers, cocci or large rods. Example Azotobacter sp.
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Family 2. Rhizobiaceae:
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It includes gram-negative rods. Some are plant pathogens and some nitrogen-fixing symbionts in leguminous roots (Rhizobium sp.).
The other families included in this order are Achromobacteriaceae, Enterobacteriaceae, Brucellaceae, Bacteriodaceae, Micrococcaceae, Neisseriaceae, Bacillaceae, Lactobacillaceae and Corynebacteriaceae.
Order V. Actinomycetales:
The order includes filamentous forms, filaments branched, reproduce by conidia, oidiospores and the like. The order comprises three families, namely, Mycobacteriaceae, Actinomycetaceae (Actinomyces) and Streptomycetaceae (Streptomyces).
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Order VI. Caryophanales:
Cells in filaments, or shorter structures, reproduce by conidia.
Order VII. Beggiatoales:
Cells solitary or in filaments, aflagellate, reproduce by fission.
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Order VIII. Myxobacteriales:
It includes rods with slime, reproduce by fission and are found in soil or dung.
Order IX. Spirochaetales:
Free living in water; body slender, spiral, aflagellate; reproduce by fission. The order comprises two familes, namely, Spirochaetaceae and Treponemataceae.
Order X. Mycoplasmatales:
It includes mostly parasitic pleomorphic forms. The order comprise one family Mycoplasmataceae.
