IMPORTANT CHARACTERISTIC OF MICROORGANISMS

•  Last few decades, great progress made three areas profoundly affect microbial classification.
• First, learned about detailed structure of microbial cells
  from the use of electron microscopy.
•  Second, microbiologists has determined biochemical and physiological characteristics of many different microorganisms. 
• Third,Sequences of nucleic acids and proteins from a wide variety of organisms.

COMPARISON OF ribosomalRNA (rRNA):

• Carl Woese in the 1970s, instrumental in demonstrating two very different groups of prokaryotic organisms: Bacteria and Archaea.
• Bacteria and Archaea, which has been classified as Monera in the five-kingdom system.
• Studies based on rRNA comparisons suggested Protista was not cohesive taxonomic unit and that it should be divided into three or more kingdoms.
• Studies and others have led many taxonomists to conclude that the five-kingdom system is too simple.
• A number of alternatives  suggested,that microbiologists believe that organisms should be divided among three domains: Bacteria (the true bacteria or eubacteria), Archaea, and Eucarya (all eucaryotic organisms).

• A brief description of the three domains and of the microorganisms placed in them follows:
• Bacteria are prokaryotes that are usually single-celled organisms .
  
• Most have cell walls that contain the structural molecule peptidoglycan.
• They are abundant in soil, water, and air and are also major inhabitants of our skin, mouth, and intestines. 
• Some bacteria live in environments that have extreme temperatures, pH, or salinity.
• some bacteria cause disease, many play more beneficial roles such as cycling elements in the biosphere, breaking down dead plant and animal material, and producing vitamins. 
• Cyanobacteria produce significant amounts of oxygen through the process of photosynthesis.
• Archaea are prokaryotes that are distinguished from Bacteria by many features, most notably their unique ribosomal RNA sequences.
• Unusual metabolic characteristics, such as the methanogens, which generate methane gas.
• Many archaea are found in extreme environments. Pathogenic archaea have not yet been identified. 
• Domain Eukarya includes microorganisms classified as protists or Fungi. Animals and plants are also placed in this domain.
• Protists are generally larger than prokaryotes and include unicellular algae, protozoa, slime molds, and water molds. 
• Algae are photosynthetic protists that together with the cyanobacteria produce about 75% of the planet’s oxygen. They are also the foundation of aquatic food chains.
• Protozoa are unicellular, animal-like protists that are usually motile. 
• Many free-living protozoa function as the principal hunters and grazers of the microbial world. 
• Nutrients by ingesting organic matter and other microbes.
• Many different environments and normal inhabitants of the intestinal tracts
  of animals, where they aid in digestion of complex materials such as cellulose.
• Slime molds are protists like protozoa in one stage of their life cycle, but are like fungi in another.
•  protozoan phase, they hunt and engulf food particles, consuming decaying vegetation and other microbes. 
• Water molds, implies,that are found on the surface water of freshwater sources and moist soil. They feed on decaying vegetation such as logs and mulch. 
• Some water molds has produced devastating plant infections, including Great Potato Famine of 1846–1847.
• Fungi are   diverse group of microorganisms ranges from unicellular forms (yeasts) to molds and mushrooms.
• Molds and mushrooms are multicellular fungi that form thin, threadlike structures called hyphae.
• They absorb nutrients from their environment, including the organic molecules that they used as a source of carbon and energy. 
• Because of their metabolic capabilities, many fungi play beneficial roles, including making bread rise, producing antibiotics, and decomposing dead organisms. 
• Other fungi cause plant diseases and diseases in humans and other animals.
• Viruses are acellular entities that invade a host cell in
  order to replicate.
•  They are smallest to all microbes (the smallest is 10,000 times smaller than a typical bacterium).
• Small size belives their power—they cause many animal and plant diseases and have caused epidemics that have shaped human history. 
• The diseases that cause include smallpox, rabies, influenza, AIDS, the common cold, and some cancers.

 THIS IS THE  NOTES OF HISTORY AND SCOPE OF MICROBIOLOGY.IF YOU LIKEMY NOTES PLEASE FOLLOW MY BLOG EVERYDAY.THANK YOU