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Biology / Bacteria

Prokaryotic Bacteria of Monera Kingdom

Kingdom Monera consists of mostly cyanobacteria and bacteria. All cyanobacteria and bacteria are unicellular and prokaryotic microorganisms, i.e. they are not having any distinctive nucleus. Prokaryotic bacteria is a single cell and acts as an organism. They appear in different shapes, Rod shaped are bacteria called Bacillus, Spherical shaped bacteria are called Coccus, Spiral coiled are called Spirillum, Comma shaped bacteria are called Vibrio, etc.

Facts about Bacteria

  • Bacteria was first observed by Anton Van Leeuwenhoek, who called them "Animalcules". The term bacteria was first coined by Christian Gottfried Ehrenberg.

  • Smallest bacteria is Mycoplasma / PPLO (Pleuropneumonia like Organism) and largest bacteria is Epulopiscium fishelsoni.

  • Based on the properties of cell walls, bacteria is divided into 2 types, Gram positive and Gram negative. Hans Christian Gram developed a special staining technique known as Gram staining to identify the two types of bacterial cells. Thick walled bacteria (Gram positive) will retain the color of staining and the thin walled (Gram negative) bacteria will not retain the color.

    Because of thin cell wall, the Gram negative bacteria have an outer membrane surrounding the cell wall. This is made up of lipid and polysaccharides and hence the outer membrane is also known as LPS layer.

  • In the cytoplasm of the bacteria, the main DNA lies bare without being enclosed in a nucleus. Such DNA is known as Nucleoid/Genophore/Bacterial chromosomes. The bacterial cytoplasm is devoid of all the cell organelles of eukaryotes except ribosomes.

  • The bacterial cytoplasm has extrachromosomal self replicating autonomous circular DNA molecules known as Plasmids. Plasmids provide anti-biotic resistance to the bacterial cells in which they are present. Plasmids also provide the bacteria, a property of using certain unusual substances as source of energy.

  • Antibiotics are chemicals released by one group of organisms against the other. In the year 1929, Alexander Fleming discovered first antibiotic chemical, Penicillin in the fungus Penicillium notatum.

  • Bio-remediation - It is a method of using laboratory cultured microbes and their mixtures to clean up environmental pollution.

Useful and Harmful Bacteria

All the bacteria are not harmful to the human beings. There are some bacteria, which are very much useful to the humankind.

Useful Bacteria

Some important useful bacteria and their usefulness are given below,

  • Rhizobium - It symbiotically lives with roots of the plants known as legumes and fixes atmospheric Nitrogen.

  • Azotobacter, Rhodospirillum and Azospirillum - These 3 are free living Nitrogen fixing soil bacteria. Today in India, Azospirillum is being used as an important bio-fertilizer in crops like Sorghum, Bajra and Ragi.

  • Bacillus thuringiensis (Bt) - It is most widely used bio-pesticide in the world. Cry1Ac gene, which creates protein in the bacteria, is taken out and put into the embryo of a plant. So, when an insect eats any part of the plant, the insect dies. Bt Toxin is a protein that is removed from the bacteria and thrown as a pesticide.

  • Streptomyces - Many antibiotics are produced from the several species of genus Streptomyces, for example anti-biotic Streptomycin.

  • Escherichia coli - E. coli is the most widely used bacterium in genetic experiments.

  • Lactobacillus - It is used for commercial production of lactic acid. It turns milk into curd.

  • Oil Zapper - It is a mixture of 4 different bacteria made by scientists of TERI (The Energy and Resources Institute, previously Tata Energy and Research Institute) to clear away oil pollutants from contaminated soil and water. Bacteria Oilivorous-S is also used for clearing pollution due to oil sludge.

Harmful Bacteria

Some important bacterial diseases and the names of the bacteria causing them are given below,

  • Cholera - Vibrio cholerae

  • TB - Mycobacterium tuberculosis

  • Leprosy - Mycobacterium leprae

  • Typhoid - Salmonella typhi

  • Pneumonia - Streptococcus pneumoniae

  • Tetanus - Clostridium tetani

  • Botulism (Food poisoning) - Clostridium botulinum

  • Diphtheria - Corynebacterium diphtheriae

  • Pertussis - Bordetella pertussis

  • Syphilis - Treponema pallidum

  • Gonorrhoea - Neisseria gonorrhoeae

  • Anthrax - Bacillus anthracis