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Microbiology

Microbiology (from Ancient Greek|Greek , ''mīkros'', "small"; , ''bios'', "life"; and , ''-logy|-logia'') is the study of ''microorganisms'', which are unicellular or cell-cluster microscopic organisms. This includes eukaryotes such as fungi and protists, and prokaryotes. Viruses, 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. 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. 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.

History

Ancient

The existence of microorganisms was hypothesized for many centuries before their actual discovery in the 17th century. Theories on microorganisms were first made by the Ancient Rome|Roman scholar Marcus Terentius 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.''Varro On Agriculture'' 1,xii Loeb

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.Ibrahim B. Syed, Ph.D. (2002). "Islamic Medicine: 1000 years ahead of its times", ''The Islamic Medical Association of North America|Journal of the Islamic Medical Association'' '''2''', p. 2–9. 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.David W. Tschanz, MSPH, PhD (August 2003). "Arab Roots of European Medicine", ''Heart Views'' '''4''' (2). When the Black Death bubonic plague reached al-Andalus in the 14th century, Ibn Khatima hypothesized that infectious diseases are caused by "Microorganisms|minute bodies" which enter the human body and cause disease. 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 and observed, nor 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.

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. The name "bacterium" was introduced much later, by Christian Gottfried Ehrenberg|Ehrenberg in 1828, derived from the Greek language|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. The field of '''bacteriology''' (later a subdiscipline of microbiology) is generally considered to have been founded in the 19th century by Ferdinand Cohn, a botanist whose studies on algae and Phototroph|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. Louis Pasteur and Robert Koch were contemporaries of Cohn’s and are often considered to be the founders of '''medical microbiology'''. 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. Pasteur also designed methods for food preservation (pasteurization) and vaccines against several diseases such as anthrax, fowl cholera and rabies. 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. 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. Beijerinck made two major contributions to microbiology: the discovery of viruses and the development of enrichment culture techniques. 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. He was responsible for the first isolation and description of both nitrifying bacteria|nitrifying and nitrogen-fixing bacteria.

Fields

The field of microbiology can be generally divided into several subdisciplines:
- '''Microbial physiology''': The study of how the microbial cell functions biochemically. Includes the study of microbial growth, microbial metabolism and bacterial cell structure|microbial cell structure.
- '''Microbial genetics''': The study of how genes are organized and regulated in microbes in relation to their cellular functions. Closely related to the field of molecular biology.
- '''Cellular microbiology''': A discipline bridging microbiology and cell biology.
- '''Medical microbiology''': The study of the pathogenic microbes and the role of microbes in human illness. Includes the study of microbial pathogenesis and epidemiology and is related to the study of disease pathology and immunology.
- '''Veterinary microbiology''': The study of the role in microbes in veterinary medicine or animal taxonomy.
- '''Environmental microbiology''': The study of the function and diversity of microbes in their natural environments. Includes the study of microbial ecology, microbially-mediated nutrient cycle|nutrient cycling, geomicrobiology, microbial diversity and bioremediation. Characterisation of key bacterial habitats such as the rhizosphere and phyllosphere, soil and groundwater ecosystems, open oceans or extreme environments (extremophiles).
- '''Evolutionary microbiology''': The study of the evolution of microbes. Includes the study of bacterial systematics and taxonomy.
- '''Industrial microbiology''': The exploitation of microbes for use in industrial processes. Examples include industrial fermentation and wastewater treatment. Closely linked to the biotechnology industry. This field also includes brewing, an important application of microbiology.
- '''Aeromicrobiology''': The study of airborne microorganisms.
- '''Food microbiology''': The study of microorganisms causing food spoilage and foodborne illness. Using microorganisms to produce foods, for example by fermentation.
- '''Pharmaceutical microbiology''': the study of microorganisms causing pharmaceutical contamination and spoil
- '''Agricultural microbiology''': The study of agriculturaly important microorganisms. (Jobs with the Center For Disease Control and Prevention requires a degree in microbiology for most positions)

Benefits

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 two-hybrid screening|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. 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. 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. 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). Recent research has suggested that microorganisms could be useful in the treatment of cancer. Various strains of non-pathogenic Clostridium|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.