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Bacteria : General Characteristics & Its Economic Importance

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Bacteria are the most abundant group of microorganisms in nature. It is found everywhere on the planet,such as hot spring,deep ocean,deserts and even thrive inside our intestine.The term bacterium was given by Ehrenberg.The branch which is deals with bacteria is known as Bacteriology.Unlike many organisms,bacteria have no natural death.

Smallest bacteria: Dialister pneumonsintes

Largest bacteria: Epulopiscium fishelsoni


Microbiology Study Materials

  • Microbiology Multiple Choice Questions (MCQ)
    Multiple Choice Questions on Microbiology: Bacteria, viruses, Bacterial reproduction , Food microbiology, Industrial Microbiology, Industrial Microbiology and more
  • Microbiology Notes
    Microbiology Notes includes: Archaebacteria, Cyanobacteria, Eubacteria, Reproduction in Bacteria, Bacterial diseases and more

General Characteristics of Bacteria

  • Bacteria are prokaryotic organisms (Kingdom:Monera), without cell defined organelles like mitochondria,Golgi bodies,Endoplasmic reticulum.,etc
  • Microscopic,unicellular,they may occur singly or aggregations to form colonies.
  • They possess rigid cell wall. Cell wall is made up of peptidoglycan (Mureins) and Lipo polysaccharides.
  • Absence of well defined nucleus.i.e., DNA is not enclosed in a nuclear membrane.
  • Ribosomes are scattered in the cytoplasmic matrix and are of 70S type.
  • The plasma membrane is invaginated to form mesosomes.
  • Most of the bacteria are heterotrophic.Some bacteria are autotrophic, possess bacteriochlorophyll, which is not in plastids.Instead it is found scattered.
  • Motile bacteria possess one or more flagella.
  • The common method of multiplication is binary fission.
  • True sexual reproduction is lacking,but genetic recombination occurs by conjugation ,transformation and transduction.

Shape of Bacteria

1.Cocci- Spherical or ellipsoidal

  • Micrococci- ex:Micrococcus
  • Diplococci ex:Diplococcus pneumoniae
  • Streptococci- ex:Streptococcus
  • Staphylococci- ex:Staphylococcus aurens
  • Tetracocci- ex:Genus Micrococcus often divide in two planes to form square groups of 4 cells called Tetrad
  • Sarcine- ex:Sarcina lutea

2.Bacilllus- Rod shaped ex:Bacillus subtilis

  • Vibrio- ex: Vibrio chlorae

3.Spirillum- Spiral shaped ex:Spirillum volutans

4.Other shapes

  • Mycellium - ex: Streptomyces
  • Pleomorphic- ex: Corynebacterium diphtheriae

Learn more

Bacteria as decomposers

Soil fertility

  • Nitrifying bacteria –Nitrosomonas & Nitrobacter
  • Ammonifying bacteria
  • Nitrogen fixing type of bacteria-Rhizobium leguminosarum, Clostridium & Azotobacter

Food that use bacteria in their production include

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  • Soy sauce-Pediococcus species
  • Cheese-Lactobacillus
  • Vinegar-Acinetobacter species

Bacteria in various industries

Fibre retting

  • Clostridium felsineum & Clostridium pectinovorum

Industrial production of organic compound

  • Acetone & Isopropanol-Clostridium species
  • Acrylic acid & Proplene Glycol- Bacillus species

Bacteria in dairy products

  • Lactic acid bacteria

Bacteria in the production of vitamins

  • Riboflavin (Vitamin B) - Clostridium butylicum
  • Cobalamine (Vitamin B12) -Pseudomonas denitrificans

Bacteria in the production of antibiotics

  • Bacitracin- Bacillus subtilis
  • Aureomycin – Streptomyces species
  • Terramycin – Streptomyces rimosus
  • Streptomycin-Streptomyces griseus

Bacteria in the production of enzymes

  • Streptokinase-Streptococcus pyogenes
  • Proteokinase- Bacillus subtilis
  • Amylase-Bacillus species

Bacteria in the production of Steroids

  • Cornyebacterium & Streptomyces


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