Introduction to Microbes and Classification

Here today we will study which organisms do we have to study in microbiology.

Microbiology includes study of all micro-organisms i.e. it includes Bacteria's , Viruses , Fungi , Protozoans and Algae. Some of them are prokaryotic and some of them are Eukaryotic. Now let us see the difference between them-
Image result for prokaryotic and eukaryotic cells


Now let us study each of the type of microbes mentioned above -

 1. Bacterias



  • Usually size ranges from 0.2 to 100 micrometres
  • Prokaryotic , unicellular , simple internal structure 
  • Can be grown on artificial laboratory media
  • Reproduction is usually asexual characteristically by simple cell division
  • Significance- Some cause disease , some perform important role in nutrient cycles leading to fertility of soil, Useful in industries for production of compounds, some spoil while so make foods.
  • Examples - Methanococcus , Mycoplasma , etc.
Related image
2. Viruses

  • Acellular and size varies from 0.015 to 0.2 micrometres
  • They all are obligate parasites so need living host 
  • Do not grow on artifical media
  • Electron microscope is needed to see them
  • Usually they have just genetic material surrounded by protein coat 
  • Significance-Cause diseases in humans , animals , plants as well as bacteria's
  • Examples - HIV virus that causes aids , TMV(Tobacco mosaic virus) that affects plants ,etc.
Image result for hiv
3. Fungi
  • Yeasts(Unicellular)-
  1. Eukaryotic ,unicellular fungi
  2. Size varies from 5 to 10 micrometres
  3. Laboratory cultivation like bacteria's is possible
  4. Reproduction by budding , cell division or sexually
  5. Significance - Useful in production of alcoholic beverages, also used as food supplement , some cause diseases.
  6. Example-Saccharomyces cerevisiae
Image result for yeast
  • Moulds(Multicellular)
  1. Eukaryotic , multicellular fungi
  2. Size varies from 2 to 10 micrometres
  3. They have many distinctive features 
  4. Can be cultivated in laboratory
  5. reproduction by sexual or asexual processes 
  6. Significance-Responsible of decomposition of many materials, useful for industrial production of many chemicals ( including penicillin), some cause diseases in plants ,animals and humans.
  7. Example - Aspergillus niger

4. Protozoan's 

  •  Size varies from 2 to 200 micrometres
  • Eukaryotic , unicellular
  • Some can be cultivated in laboratory
  • some are intracellular parasites
  • reproduction by asexual or sexual processes
  • Significance- Food for aquatic animals and some are disease causing
  • Example- Amoeba
Image result for protozoan
5. Algae

  • Size ranges from 1 micrometre to many feet
  • Eukaryotic , can be unicellular or multicellular
  • Most occur in aquatic environments
  • contain chlorophyll and are thus photosynthetic
  • reproduction can be sexual or asexual
  • Significance- Important to production of food in aquatic environments , used as food supplements and in pharmaceutical preparations , source of agar , some produce toxic products.
  • Example - Chlamydomonas , chlorella ,etc.
Image result for chlamydomonas

  Carl Woese had used RNA studies to group all the organisms into three domains

  1. Archaea
  2. Bacteria(Eubacteria)
  3. Eukarya
But later on R.H.Whittaker divided all living organisms into five kingdoms on the basis of three criteria's-

  1. Cell type- Prokaryotic or eukaryotic
  2. Level of organisation - Solitary or colonial and unicellular or multicellular
  3. Nutritional type - Ingestive , absorptive or autotrophic
So the five kingdoms proposed by him were
  1.  Monera
  2.  Protista
  3.  Fungii
  4.  Plantae
  5.  Animalia
Image result for whittaker's five kingdom concept
The five kingdom system was not accepted by many scientists because of the lack of distinction between Archaebacteria and Eubacteria. So new six kingdom system was introduced as follows-
Image result for six kingdom concept


Hope this was easy to understand , if you have doubt you can contact me.
Now we will study the Monera kingdom , Archaebacteria , cyanobacteria and bacteria's in the next post.

 For any Query or suggestion please mail me or leave comments

 Thank you

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