1.Eubacteria:

They have either of following shapes.

a)Coccus: Micrococcus, Halococcus

b)Bacillus: Lactobacillus, Thiobacillus

c)Comma

d)Spirillum

e)Vibrio

• They reproduce by binary fission.
• Cell wall is made up of peptidoglycan.
• On the basis of gram strain; Gram +ve: Peptidoglycan thick and Gram –ve: peptidoglycan thin.
• Can occur in both oxygen abundant & oxygen deficient regions

2. Archaebacteria:

• Cell wall do not contain peptidoglycan but contain other polysaccharides.
• Cell membrane contains a single layer of glycerol hydrocarbons glycerol chains instead of bicay of phospholipid arranged tail to tail.
• Their ribosomes are insensitive to chloramphenicol (Antibiotics).
• Include methanogens (methane generating bacteria): Halophiles (salt loving) & Thermoacidophile (high temp. & acidic pH, sulfur spring, cools waste).

3.Cyanobacteria:

• Typical prokaryotes
• Evolve O2 during photosynthesis.
• Found in terrestrial and aquatic environment e.g.: Nostoc, Anabaena, Oscillatoria etc.

4. Actinomycetes:

• Majority of Actinomycetes are mycelial (as in fungi) and gram +ve.
• Reproduce by unicellular specialized spores.
• g.: Streptomycetes, Micromonospora etc.
• While in other the mycelia state is transitory and of ten limited producing no specialized spores & reproducing by fragmentation forming short rod-shaped cells.
• g.: Actinomycetes, Nocardia and Mycobacterium: medicinally important.