Microbiology

An agar plate streaked with microorganisms

Microbiology (from Greek μῑκρος, mīkros, "small"; βίος, bios, "life"; and -λογία, -logia) is the study of microorganisms, which are unicellular or cell-cluster microscopic organisms.[1] This includes eukaryote such as fungi and protists, and prokaryotes, which are bacteria and archaea. Viruses, though not strictly classed as living organisms, are also studied.[2] In short; microbiology refers to the study of life and organisms that are too small to be seen with the naked eye.

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

Microbiology is researched actively, and the field is advancing continually. We have probably only studied about one percent of all of the microbe species on Earth.[3] Although microbes were first 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.

Contents

History

Ancient

The existence of microorganisms was hypothesized for many centuries before their actual discovery in the 17th century. The first theories on microorganisms was made by Roman scholar Marcus Terentis Varro in a book titled On Agriculture in which he warns against locating a homestead in the vicinity of swamps:

“ ...and 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.[4] ”

This passage seems to indicate that the ancients were aware of the possibility that diseases could be spread by yet unseen organisms.

In The Canon of Medicine (1020), Abū Alī ibn Sīnā (Avicenna) stated that bodily secretion is contaminated by foul foreign earthly bodies before being infected.[5] He also hypothesized on the contagious nature of tuberculosis and other infectious diseases, and used quarantine as a means of limiting the spread of contagious diseases.[6]

When the Black Death bubonic plague reached al-Andalus in the 14th century, Ibn Khatima hypothesized that infectious diseases are caused by "minute bodies" which enter the human body and cause disease.[5]

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.

All these early claims about the existence of microorganisms were speculative in nature and not based on any data or science. Microorganisms were neither proven, observed, and correctly and accurately described until the 17th century. The reason for this was that all these early inquiries lacked the most fundamental tool in order for microbiology and bacteriology to exist as a science, and that was the microscope.

Antonie van Leeuwenhoek, the first microbiologist and the first to observe microorganisms using a microscope. Known as the 'Father of Microbiology'. Whilst he did not invent the microscope, he greatly developed it.

Modern

Bacteria, and other microorganisms, were first observed by Antonie van Leeuwenhoek in 1676 using a single-lens microscope of his own design. In doing so Leeuwenhoek made one of the most important discoveries in biology and initiated the scientific fields of bacteriology and microbiology.[1] The name "bacterium" was introduced much later, by Ehrenberg in 1828, derived from the Greek βακτηριον meaning "small stick". While Van Leeuwenhoek is often cited as the first microbiologist, the first recorded microbiological observation, that of the fruiting bodies of molds, was made earlier in 1665 by Robert Hooke.[7]

The field of bacteriology (later a subdiscipline of microbiology) is generally considered to have been founded by Ferdinand Cohn (1828–1898), 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.[8] Louis Pasteur (1822–1895) and Robert Koch (1843–1910) were contemporaries of Cohn’s and are often considered to be the founders of medical microbiology.[9] 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.[10] 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 work of Martinus Beijerinck (1851–1931) and Sergei Winogradsky (1856–1953), 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.[11] 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.[12] He was responsible for the first isolation and description of both nitrifying and nitrogen-fixing bacteria.[1]

Types

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

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 many human illnesses, many microbes are also responsible for many beneficial processes such as industrial fermentation (e.g. the production of alcohol 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. [13]

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.[14]

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 most sites are typically comprised of 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.[15]

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).[16]

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.[17]


References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 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?". Retrieved on 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: 143–169. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=7535888. 
  4. ↑ Varro On Agriculture 1,xii Loeb
  5. ↑ 5.0 5.1 Ibrahim B. Syed, Ph.D. (2002). "Islamic Medicine: 1000 years ahead of its times", Journal of the Islamic Medical Association 2, p. 2-9.
  6. ↑ David W. Tschanz, MSPH, PhD (August 2003). "Arab Roots of European Medicine", Heart Views 4 (2).
  7. ↑ 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. 
  8. ↑ Drews G (1999). "Ferdinand Cohn, a Founder of Modern Microbiology". ASM News 65 (8). http://www.asm.org/Articles/Ferdinand.html. 
  9. ↑ Ryan KJ, Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0-8385-8529-9. 
  10. ↑ Bordenave G (2003). "Louis Pasteur (1822-1895)". Microbes Infect. 5 (6): 553–60. PMID 12758285. 
  11. ↑ Johnson J (1998-07-01). "Martinus Willem Beijerinck". American Phytopathological Society. Retrieved on 2007-07-23.
  12. ↑ Paustian T, Roberts G. "Beijerinck and Winogradsky initiate the field of environmental microbiology". The Microbial World. Retrieved on 2007-07-23.
  13. ↑ Burkovski A (editor). (2008). Corynebacteria: Genomics and Molecular Biology. Caister Academic Press. ISBN 978-1-904455-30-1. http://www.horizonpress.com/cory. 
  14. ↑ 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. 
  15. ↑ 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. 
  16. ↑ Tannock GW (editor). (2005). Probiotics and Prebiotics: Scientific Aspects. Caister Academic Press. ISBN 978-1-904455-01-1. http://www.horizonpress.com/pro3. 
  17. ↑ 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. 

Further reading

  • Lerner, Brenda Wilmoth & K. Lee Lerner (eds) (2006). Medicine, health, and bioethics : essential primary sources (1st ed.). Thomson Gale. ISBN 1414406231. 
  • Witzany, Guenther (2008). Bio-Communication of Bacteria and its Evolutionary Interrelations to Natural Genome Editing Competences of Viruses.. Nature Precedings. hdl:10101/npre.2008.1738.1. 

See also
  • Food microbiology
  • Genetics
  • Geomicrobiology
  • Good Hygiene Practice
  • Good Microbiological Practice
  • Immunology
  • Important publications in microbiology
  • Industrial microbiology

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Microbiology: Bacteria
Pathogenic bacteria

Bacterial disease · Coley's Toxins · Exotoxin · Lysogenic cycle
Human flora

Gut flora · Skin flora · Vaginal flora
Substrate preference
Lipophilic · Saccharophilic
Oxygen preference
Aerobic · Anaerobic (Facultative, Obligate) · Microaerophile · Nanaerobe · Aerotolerant
Structures
Cell envelope
Cell membrane

Cell wall: Peptidoglycan (NAM, NAG, DAP)

Gram-positive bacteria only: Teichoic acid · Lipoteichoic acid · Endospore

Gram-negative bacteria only: Bacterial outer membrane (Porin, Lipopolysaccharide) · Periplasmic space
Outside envelope
Bacterial capsule · Slime layer · Glycocalyx
Pilus · Fimbria
Composite
Shapes
Coccus (Diplococcus)  · Bacillus · Coccobacillus
Microbiology: Virus topics
Components
Viral envelope · Capsid
Other
Table of clinically important viruses · Bacteriophage · Virus cancer link · Laboratory diagnosis of viral infections · Antiviral drug · Neurotropic virus · Oncovirus
Microbiology: Fungus
Structure
Reproduction/spore
teleomorph/sexual: Zygospore · Ascospore/Ascus · Basidiospore/Basidium/Teliospore
anamorph/asexual: Sporangium · Conidium · Chlamydospore
Other
Hypha · Haustorium · Mycelium · Cell wall
Growth patterns
Dimorphic fungi · Mold · Yeast · Mushroom