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Microbiology

An agar plate streaked with microorganisms

Microbiology (from Greek îΌá¿‘îΊΟî¿Ο‚, mä«kros, "small"; î²î―î¿Ο‚, bios, "life"; and -î»î¿î³î―î±, -logia) is the study of microorganisms, which are unicellular or cell-cluster microscopic organisms.[1] This includes eukaryotes such as fungi and protists, and prokaryotes. Viruses[2] and prions, though not strictly classed as living organisms, are also studied. In short; microbiology refers to the study of life and organisms that are too small to be seen with the naked eye. Microbiology typically includes the study of the immune system, or Immunology. Generally, immune systems interact with pathogenic microbes; these two disciplines often intersect which is why many colleges offer a paired degree such as "Microbiology and Immunology".

Microbiology is a broad term which includes virology, mycology, parasitology, bacteriology and other branches. A microbiologist is a specialist in microbiology and these other topics.

Microbiology is researched actively, and the field is advancing continually. It is estimated only about one percent of all of the microbe species on Earth have been studied.[3] Although microbes were directly observed over three hundred years ago, the field of microbiology can be said to be in its infancy relative to older biological disciplines such as zoology and botany.

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[edit] History

[edit] Ancient

The existence of microorganisms was hypothesized for many centuries before their actual discovery. The existence of unseen microbiological life was postulated by Jainism which is based on Mahavira’s teachings as early as 6th century BCE.[4]. Paul Dundas notes that Mahavira asserted existence of unseen microbiological creatures living in earth, water, air and fire.[5] Jain scriptures also describe nigodas which are sub-microscopic creatures living in large clusters and having a very short life and are said to pervade each and every part of the universe, even in tissues of plants and flesh of animals.[6] The Roman Marcus Terentius Varro made references to microbes when he warned against locating a homestead in the vicinity of swamps "because there are bred certain minute creatures which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there cause serious diseases."[7][citation needed]

In 1546 Girolamo Fracastoro proposed that epidemic diseases were caused by transferable seedlike entities that could transmit infection by direct or indirect contact, or even without contact over long distances.[citation needed]

However, early claims about the existence of microorganisms were speculative, and not based on any data or observation. Actual observation and discovery of microbes had to await the invention of the microscope in the 17th century.

[edit] Modern

Antonie van Leeuwenhoek, known as the "father of microbiology", was the first to observe microorganisms using a microscope.

in 1676, Antonie van Leeuwenhoek first observed bacteria and other microorganisms, using a single-lens microscope of his own design.[1] While Van Leeuwenhoek is often cited as the first microbiologist, Robert Hooke made the first recorded microbiological observation, of the fruiting bodies of molds, in 1665.[8]

The field of bacteriology (later a subdiscipline of microbiology) was founded in the 19th century by Ferdinand Cohn, a botanist whose studies on algae and photosynthetic bacteria led him to describe several bacteria including Bacillus and Beggiatoa. Cohn was also the first to formulate a scheme for the taxonomic classification of bacteria.[9] Louis Pasteur and Robert Koch were contemporaries of Cohn’s and are often considered to be the founders of medical microbiology.[10] Pasteur is most famous for his series of experiments designed to disprove the then widely held theory of spontaneous generation, thereby solidifying microbiology’s identity as a biological science.[11] Pasteur also designed methods for food preservation (pasteurization) and vaccines against several diseases such as anthrax, fowl cholera and rabies.[1] Koch is best known for his contributions to the germ theory of disease, proving that specific diseases were caused by specific pathogenic microorganisms. He developed a series of criteria that have become known as the Koch's postulates. Koch was one of the first scientists to focus on the isolation of bacteria in pure culture resulting in his description of several novel bacteria including Mycobacterium tuberculosis, the causative agent of tuberculosis.[1]

While Pasteur and Koch are often considered the founders of microbiology, their work did not accurately reflect the true diversity of the microbial world because of their exclusive focus on microorganisms having direct medical relevance. It was not until the late 19th century and the work of Martinus Beijerinck and Sergei Winogradsky, the founders of general microbiology (an older term encompassing aspects of microbial physiology, diversity and ecology), that the true breadth of microbiology was revealed.[1] Beijerinck made two major contributions to microbiology: the discovery of viruses and the development of enrichment culture techniques.[12] While his work on the Tobacco Mosaic Virus established the basic principles of virology, it was his development of enrichment culturing that had the most immediate impact on microbiology by allowing for the cultivation of a wide range of microbes with wildly different physiologies. Winogradsky was the first to develop the concept of chemolithotrophy and to thereby reveal the essential role played by microorganisms in geochemical processes.[13] He was responsible for the first isolation and description of both nitrifying and nitrogen-fixing bacteria.[1]

[edit] Fields

The field of microbiology can be generally divided into several subdisciplines:

(Jobs with the Center For Disease Control and Prevention requires a degree in microbiology for most positions)

[edit] Benefits

Fermenting tanks with yeast being used to brew beer

Whilst there are undoubtedly some who fear all microbes due to the association of some microbes with various human illnesses, many microbes are also responsible for numerous beneficial processes such as industrial fermentation (e.g. the production of alcohol, vinegar and dairy products), antibiotic production and as vehicles for cloning in higher organisms such as plants. Scientists have also exploited their knowledge of microbes to produce biotechnologically important enzymes such as Taq polymerase, reporter genes for use in other genetic systems and novel molecular biology techniques such as the yeast two-hybrid system.

Bacteria can be used for the industrial production of amino acids. Corynebacterium glutamicum is one of the most important bacterial species with an annual production of more than two million tons of amino acids, mainly L-glutamate and L-lysine.[14]

A variety of biopolymers, such as polysaccharides, polyesters, and polyamides, are produced by microorganisms. Microorganisms are used for the biotechnological production of biopolymers with tailored properties suitable for high-value medical application such as tissue engineering and drug delivery. Microorganisms are used for the biosynthesis of xanthan, alginate, cellulose, cyanophycin, poly(gamma-glutamic acid), levan, hyaluronic acid, organic acids, oligosaccharides and polysaccharide, and polyhydroxyalkanoates.[15]

Microorganisms are beneficial for microbial biodegradation or bioremediation of domestic, agricultural and industrial wastes and subsurface pollution in soils, sediments and marine environments. The ability of each microorganism to degrade toxic waste depends on the nature of each contaminant. Since sites typically have multiple pollutant types, the most effective approach to microbial biodegradation is to use a mixture of bacterial species and strains, each specific to the biodegradation of one or more types of contaminants.[16]

There are also various claims concerning the contributions to human and animal health by consuming probiotics (bacteria potentially beneficial to the digestive system) and/or prebiotics (substances consumed to promote the growth of probiotic microorganisms).[17]

Recent research has suggested that microorganisms could be useful in the treatment of cancer. Various strains of non-pathogenic clostridia can infiltrate and replicate within solid tumors. Clostridial vectors can be safely administered and their potential to deliver therapeutic proteins has been demonstrated in a variety of preclinical models.[18]


[edit] See also

[edit] References

  1. ^ a b c d e f Madigan M, Martinko J (editors) (2006). Brock Biology of Microorganisms (11th ed.). Prentice Hall. ISBN 0-13-144329-1. 
  2. ^ Rice G (2007-03-27). "Are Viruses Alive?". http://serc.carleton.edu/microbelife/yellowstone/viruslive.html. Retrieved 2007-07-23. 
  3. ^ Amann RI, Ludwig W, Schleifer KH (1995). "Phylogenetic identification and in situ detection of individual microbial cells without cultivation". Microbiol. Rev. 59 (1): 143–169. PMID 7535888. 
  4. ^ Mahavira is dated 599 BCE - 527 BC. See. Dundas, Paul; John Hinnels ed. (2002). The Jains. London: Routledge. ISBN 0-415-26606-8.  p. 24
  5. ^ Dundas, Paul (2002) p. 88
  6. ^ *Jaini, Padmanabh (1998). The Jaina Path of Purification. New Delhi: Motilal Banarsidass. ISBN 81-208-1578-5.  p. 109
  7. ^ Varro on Agriculture 1, xii Loeb.
  8. ^ Gest H (2005). "The remarkable vision of Robert Hooke (1635-1703): first observer of the microbial world". Perspect. Biol. Med. 48 (2): 266–72. doi:10.1353/pbm.2005.0053. PMID 15834198. 
  9. ^ Drews G (1999). "Ferdinand Cohn, a Founder of Modern Microbiology". ASM News 65 (8): 547. 
  10. ^ Ryan KJ, Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0-8385-8529-9. 
  11. ^ Bordenave G (2003). "Louis Pasteur (1822-1895)". Microbes Infect. 5 (6): 553–60. doi:10.1016/S1286-4579(03)00075-3. PMID 12758285. 
  12. ^ Johnson J (2001). "Martinus Willem Beijerinck". APSnet. American Phytopathological Society. http://www.apsnet.org/Education/feature/TMV/intro.html. Retrieved May 2, 2010. 
  13. ^ Paustian T, Roberts G (2009). "Beijerinck and Winogradsky Initiate the Field of Environmental Microbiology". Through the Microscope: A Look at All Things Small (3rd ed.). Textbook Consortia. ⧠1–14. http://www.microbiologytext.com/index.php?module=Book&func=displayarticle&art_id=32. Retrieved May 2, 2010. 
  14. ^ Burkovski A (editor). (2008). Corynebacteria: Genomics and Molecular Biology. Caister Academic Press. ISBN 978-1-904455-30-1. http://www.horizonpress.com/cory. 
  15. ^ Rehm BHA (editor). (2008). Microbial Production of Biopolymers and Polymer Precursors: Applications and Perspectives. Caister Academic Press. ISBN 978-1-904455-36-3. http://www.horizonpress.com/biopolymers. 
  16. ^ Diaz E (editor). (2008). Microbial Biodegradation: Genomics and Molecular Biology (1st ed.). Caister Academic Press. ISBN 978-1-904455-17-2. http://www.horizonpress.com/biod. 
  17. ^ Tannock GW (editor). (2005). Probiotics and Prebiotics: Scientific Aspects. Caister Academic Press. ISBN 978-1-904455-01-1. http://www.horizonpress.com/pro3. 
  18. ^ Mengesha et al. (2009). "Clostridia in Anti-tumor Therapy". Clostridia: Molecular Biology in the Post-genomic Era. Caister Academic Press. ISBN 978-1-904455-38-7. 


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