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B.Sc. Microbiology II Bacteriology Unit III Microbial Diversity


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Microbial Diversity

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B.Sc. Microbiology II Bacteriology Unit III Microbial Diversity

  1. 1. Microbial Diversity Course: B.Sc. Microbiology Sem II Sub: Bacteriology Unit III
  2. 2. Archaebacteria • The Archaea constitute a domain or kingdom of single-celled microorganisms. • These microbes are prokaryotes, meaning that they have no cell nucleus or any other membrane-bound organelles in their cells. • Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Kingdom Monera), but this classification is outdated. • Archaeal cells have unique properties separating them from the other two domains of life: Bacteria and Eukaryota. • The Archaea are further divided into four recognized phyla. Classification is difficult because the majority have not been studied in the laboratory and have only been detected by analysis of their nucleic acids in samples from their environment.
  3. 3. • Archaea were initially viewed as extremophiles living in harsh environments, such as hot springs and salt lakes, but they have since been found in a broad range of habitats, including soils, oceans, marshlands and the human colon and navel. • Archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. • Archaea are a major part of Earth's life and may play roles in both the carbon cycle and the nitrogen cycle. • No clear examples of archaeal pathogens or parasites are known, but they are often mutualists or commensals. • One example is the methanogens that inhabit the human gut and the ruminant gut, where their vast numbers aid digestion. • Methanogens are used in biogas production and sewage treatment, and enzymes from extremophile archaea that can endure high temperatures and organic solvents are exploited in biotechnology.
  4. 4. Methanogens • Methanogens are microorganisms that produce methane as a metabolic byproduct in anoxic conditions. They are classified as archaea, a domain distinct from bacteria. • They are common in wetlands, where they are responsible for marsh gas, and in the digestive tracts of animals such as ruminants and humans, where they are responsible for the methane content of belching in ruminants and flatulence in humans. • In marine sediments the biological production of methane, also termed methanogenesis, is generally confined to where sulfates are depleted, below the top layers. • Moreover, the methanogenic archaea populations play an indispensable role in anaerobic wastewater treatments. Others are extremophiles, found in environments such as hot springs and submarine hydrothermal vents as well as in the "solid" rock of the Earth's crust, kilometers below the surface. • Not to be confused with methanotrophs which rather consume methane for their carbon and energy requirements.
  5. 5. Halophiles • Halophiles are organisms that live in high salt concentrations. They are a type of extremophile organism. The name comes from the Greek word for "salt-loving". • While most halophiles are classified into the Archaea domain, there are also bacterial halophiles and some eukaryota, such as the alga Dunaliella salina or fungus Wallemia ichthyophaga. • Some well-known species give off a red color from carotenoid compounds, notably bacteriorhodopsin. • Halophiles can be found anywhere with a concentration of salt five times greater than the salt concentration of the ocean, such as the Great Salt Lake in Utah, Owens Lake in California, the Dead Sea, and in evaporation ponds.
  6. 6. Thermophile • A thermophile is an organism — a type of extremophile — that thrives at relatively high temperatures, between 41 and 122 °C (106 and 252 °F). Many thermophiles are archaea. Thermophilic eubacteria are suggested to have been among the earliest bacteria.[ • Thermophiles are found in various geothermally heated regions of the Earth, such as hot springs like those in Yellowstone National Park (see image) and deep sea hydrothermal vents, as well as decaying plant matter, such as peat bogs and compost. • Unlike other types of bacteria, thermophiles can survive at much hotter temperatures, whereas other bacteria would be damaged and sometimes killed if exposed to the same temperatures. • Professor Zachary Studniberg, from Cambridge University, wrote in his book 'The Function of Extremophiles' that they are the most unique organism on the planet in terms of their contribution to modern life. • As a prerequisite for their survival, thermophiles contain enzymes that can function at high temperatures. Some of these enzymes are used in molecular biology (for example, heat-stable DNA polymerases for PCR), and in washing agents.
  7. 7. Eubacteria • Eubacteria is a bacterium of a large group typically having simple cells with rigid cell walls and often flagella for movement. The group comprises the ‘true’ bacteria and cyanobacteria, as distinct from archaea. • Bacteria constitute a large domain of prokaryotic microorganisms. • Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. • Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. • Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. They are also known to have flourished in manned spacecraft.
  8. 8. References Books: 1. Biology of microorganisms By M. T. Madigan, J. M. Martinko, D. A. Stahl and D. P. Clark