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Introduction to plant pathogenic microorganism
Learn Agricultural Microbiology with Braimy – B.Sc. agriculture
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They have either of following shapes.

a)Coccus: Micrococcus, Halococcus

b)Bacillus: Lactobacillus, Thiobacillus




  • 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

  1. 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).


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

  1. 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.
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