Here is a compilation of term papers on ‘Microbiology’. Find paragraphs, long and short term papers on ‘Microbiology’ especially written for school and college students.
Term Paper on Microbiology
Term Paper Contents:
- Term Paper on the Definition of Microbiology
- Term Paper on the History of Microbiology
- Term Paper on the Beginnings of Microbiology
- Term Paper on the Scope and Future of Microbiology
- Term Paper on the Transition Period of Microbiology
- Term Paper on the Golden Age of Microbiology
- Term Paper on the Types of Microbiology
- Term Paper on the Development of Microbiology
- Term Paper on the Benefits of Microbiology
- Term Paper on Modern Microbiology
Term Paper # 1. Definition of Microbiology:
Microbiology is the branch of science that deals with the study of small organisms that can be seen only under microscope. Such organisms are called microorganisms which are believed to be the most primitive life on earth. They are existing since long but could be discovered only after the invention of microscope.
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It ia a multi-disciplinary science of microorganisms and the prefix ‘micro’ generally refers to an object small enough so that microscopic examination is required for detailed visualization. Thus it is the scientific study of microorganisms, including a diverse group of simple life forms like protozoa, algae, molds, bacteria and viruses.
Microbiology is concerned with the structure, function, classification and ways of controlling and using their activities. The earlier works done by Antony Van Leauwenhoek (1632 – 1723), and later in 19th century by Louis Pasteur (1822- 1893) and Robert Koch (1843-1910) etc. laid the foundations of this subject.
Microbiology is the science which includes the study of the occurrence and significance of bacteria, fungi, protozoa and algae which are the beginning and ending of intricate food chains upon which all life depends.
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These food chains begin wherever photosynthetic organisms can trap light energy and use it to synthesize large molecules from carbon dioxide, water and mineral salts forming the proteins, fats and carbohydrates which all other living creatures use for food.
Within and on the bodies of all living creatures, as well as in soil and water, micro-organisms build up and change molecules, extracting energy and growth substances. They also help to control population levels of higher animals and plants by parasitism and pathogenicity.
When plants and animals die, their protective antimicrobial systems cease to function so that, sooner or later, decay begins liberating the smaller molecules for re-use by plants.
Without human intervention, growth, death, decay and re-growth would form an intricate web of plants, animals and micro-organisms, varying with changes in climate and often showing apparently chaotic fluctuations in populations of individual species, but inherently balanced in numbers between producing, consuming and recycling groups.
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In the distant past, these cycles of growth and decay would have been little influenced by the small human population that could be supported by the hunting and gathering of food. From around 10000 BC however, the deliberate cultivation of plants and herding of animals started in some areas of the world.
The increased productivity of the land and the improved nutrition that resulted led to population growth and a probable increase in the average lifespan. The availability of food surpluses also liberated some from daily toil in the fields and stimulated the development of specialized crafts, urban centres, and trade – in short, civilization.
Term Paper # 2. History of Microbiology:
Bacteria were first observed by Anton van Leeuwenhoek in 1676 using a single-lens microscope of his own design. While Antony 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.
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The field of bacteriology (later a sub-discipline 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. Ferdinand Cohn was also the first to formulate a scheme for the taxonomic classification of bacteria.
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.
Louis 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.
Robert Koch is best known for his contributions to the germ theory of disease, proving that specific diseases were caused specific pathogenic microorganisms by the application of what has become known as the Koch’s postulates.
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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 Louis Pasteur and Robert 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 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.
Martinus 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.
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Sergei 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 and nitrogen-fixing bacteria.
Term Paper # 3. Beginnings of Microbiology:
Ironically, an interest in microscopic objects was developing even as the tragedy and sacrifice of Eyam were unfolding. In 1665, a scientist named Robert Hooke published a major work called Micrographie. Hooke did not invent the microscope (that distinction is generally attributed to Zacharias Janssen, a spectacle-maker from Middleburg, the Netherlands), but he did give it respectability.
Hooke’s writings awakened the learned of Europe to the world of very small objects and creatures. Among his illustrations were representations of the eye of a fly, stinger of a bee, structure of a feather, shell of a protozoan, and plantlike form of a mold. He also described a slice of cork and suggested that the cork was composed of compartments, which he called cells. By this account he secured for himself a place in the history of cell biology.
Other scientists were quick to follow Hooke’s lead. For example, the Dutch naturalist Jan Swammerdam described tiny bodies, the red blood cells, in samples of blood. Another Dutchman, Regnier de Graaf, discovered cell clusters called follicles in the animal ovary (known today as Graffian follicles). Still another scientist, the Italian physiologist Marcello Malpighi, described the tiny capillaries of an animal’s cardiovascular system.
The discoveries by Hooke, Swammerdam, and other scientists showed that the microscope was an important tool for unlocking the secrets of nature. It is not surprising, therefore, that genuine interest was forthcoming when Anton van Leeuwenhoek revealed his descriptions of microorganisms in the 1670s.
Anton Van Leeuwenhoek:
Anton van Leeuwenhoek was a draper and haberdasher and the owner of a dry goods business in Delft, the Netherlands. His father had made the baskets used to pack Delft china off to world markets, and van Leeuwenhoek enjoyed a comfortable living selling silk, wool, cotton, buttons, and other supplies. He was head of the City Council, inspector of weights and measures, and court surveyor.
In his spare time, he ground pieces of glass into fine lenses, placing them between two silver or brass plates riveted together. Later he added an adjustable device for holding tiny specimens. Gradually, he developed a skill that would remain unmatched for many generations.
Van Leeuwenhoek’s lenses were no larger than the head of a pin, but they served him well. By most accounts they could magnify an object over 200 times. Initially he used the lenses to inspect the quality of cloth, but as his fascination with microscopic objects developed, he examined hair fibers, skin scales, eye lenses, blood cells, and even samples of his own feces. At one point, van Leeuwenhoek observed tiny sperm cells and speculated that they contain microscopic embryos transferred to the female for nourishment and development.
Van Leeuwenhoek’s work did not go unnoticed or unreported. Probably the only scientific group of that period was the Royal Society of London, but correspondence with this group was tenuous because England and the Netherlands were bitter rivals for commercial treasures Regnier de Graaf, a fellow of the Royal Society, dispatched a letter to the members in 1673 urging them to contact van Leeuwenhoek. They did so, and van Leeuwenhoek was soon sending along his illustrations and observations. The contact was maintained for the next 50 years.
In September 1674, van Leeuwenhoek filled a glass with greenish, cloudy water from a marshy lake outside Delft and placed a sample under his lens. The water teemed with tiny microorganisms, which he called animalcules. His curiosity aroused, van Leeuwenhoek soon located the animalcules in rainwater, in material from his own teeth and feces, and eventually in most of the specimens he examined. The creatures astonished him at first, then delighted and perplexed him as he pondered their origin and purpose.
Van Leeuwenhoek’s sketches were elegant in detail and clarity. In succeeding letters, he outlined structural details of the familiar protozoa known today as Paramecium and Amoeba, and he described the thread like fungi, as well as certain microscopic algae. A particularly noteworthy letter, written in 1683, included drawings of what are now believed to be bacteria in the form of rods, spheres, and spirals.
His work was performed exclusively with single-lens microscopes, of which he constructed about 550. His studies opened the door to a completely new concept of the makeup of all living things.
In 1680, van Leeuwenhoek was elected to fellowship in the Royal Society and, with Isaac Newton and Robert Boyle, he became one of the most famous men of his times. Peter the Great of Russia and the Queen of England came to peer into his microscopes.
His technique was so fastidious that when some of his slides were discovered 300 years later, scientists found perfectly preserved specimens of cotton seeds, slices of cork, and the optic nerve of a cow. In all, van Leeuwenhoek bombarded the Royal Society with over 200 letters about his findings. He died in 1723 at the age of 90, his advanced age itself a notable achievement.
Van Leeuwenhoek was a very suspicious and secretive person. He invited no one to work with him, nor did he show anyone how to grind lenses or construct a microscope. This is one reason why interest in the microorganisms waned after his death. Another reason, and perhaps of more significance, is that scientists of the day saw the microorganisms merely as curiosities of nature.
In the 1700s, disease was still shrouded in magic and mysticism, and few people believed that microorganisms could cause disease in so lofty a creature as the human being. Thus, the substantial development of microbiology would be delayed until the technology for an efficient microscope emerged and until an association was drawn between microorganisms and disease. This was not to happen until the late 1800s.
Term Paper # 4. Scope and Future of Microbiology:
The microbes not only need to be understood as causative agents of diseases but are also useful to us as contributors in food production, antibiotic manufacture, vaccine development and environmental management.
Recently the subject had also allowed us to explore and control the following diseases; Foot and mouth disease, Asian Bird Flu, SARS (Severe Acute Respiratory Syndrome), West Nile Virus, and Monkey-pox.
We are now also exploring more Prions related diseases causing a type of amyloid diseases (characterized by normal brain protein being altered and changing into fibres); at times called as: Transmissible Spongiform Encephalopathy (TCS).
Creutzfeldt-Jakob disease in humans (CJD), Bovine Spongiform Encephalopathy (BSE) also known as mad-cow disease, chronic wasting disease (CWD) in deer and elk Kuri in human Feline spongiform Encephalopathy (FSE), and Transmissible mink Encephalopathy (TME). The interest is growing in various zoonotic diseases (of animals that can pass to humans) due to their close proximity of rearing or habitation.
Due to undergoing environmental changes, global warming and related climate changes, various mathematical models are trying to understand the impact of these factors on disease causing microbes of their respective hosts. Immunoparasitology has helped us in the past to understand various pathogens. As the bacteria alone account for 50% of the biomass of carbon and over 90% of the biomass of Nitrogen and phosphorus combined on our planet, such claims seem to be true.
The future microbiology is already an integrative microbiology incorporating inputs from microbial physiology, microbial genetics, microbial ecology and microbial pathogenesis using tools and dialects of various sub disciplines.
The use of microbes in nanotechnology has brought microbiology to engineering and physics. And recent discoveries indicate that microbes also play roles in determining animal behaviour, bringing microbiology to the realm of psychology. Hence the 21st century microbiology is already an integrative science with lots of challenges and benefits to reap.
Term Paper # 5. The Transition Period of Microbiology:
Biology of the 1700s was a body of knowledge without a focus. Basically, it consisted of observations of plant and animal life and the attempts by scientists to place the organisms in some logical order.
New World explorers returned to Europe regularly with specimens to be described and catalogued, and interest in the variety of life forms grew steadily. The dominant figure of the era was Carolus Linnaeus, a Swedish botanist who brought all the plant and animal forms together under one great classification scheme. His book, Systema Naturae, was first published in 1735.
A few scientists continued to explore the microscopic world. In 1718, for example, Louis Joblot published a treatise on protozoa, and in 1725 Abraham Tremblay described the simple animal known as the hydra. However, scientists generally did not think that tiny living organisms could cause infection.
Rather, they believed that an infectious disease spread by an altered chemical quality of the atmosphere, an entity called miasma. Miasma arose from decaying or diseased bodies known as miasms. The miasma theory figured prominently in medical thinking well into the 1800s.
As the years unfolded, some biologists began to scrutinize the laws of nature and to question the origin of living things as they exist today. The resulting controversy surrounding spontaneous generation could be answered only by experimentation. Explorations of this type reached to the very essence of biology and bridged the gap between van Leeuwenhoek’s time and the mid-1800s.
Spontaneous Generation:
In the fourth century B.C., Aristotle wrote that flies, worms, and other small animals arose from decaying matter without the need of parent organisms. His observations laid the basis for the doctrine of spontaneous generation, a belief that lifeless substances could give rise to living creatures.
Indeed, in the early 1600s, the eminent Flemish physician Jan Baptista van Helmont lent credence to the belief when he observed rats “originate” from wheat bran and old rags. Common people embraced the idea, for even they could see slime “breeding” toads and meat “generating” wormlike maggots.
Among the first to dispute the theory of spontaneous generation was the Florentine scientist Francesco Redi. Noting van Leeuwenhoek’s complex descriptions of tiny animals, Redi reasoned that flies had reproductive organs. He suggested that flies land on pieces of exposed meat and lay their eggs, which then hatch to maggots.
This would explain the “spontaneous” appearance of maggots. In the 1670s, Redi performed a series of tests in which he covered jars of meat with fine lace, thereby preventing the entry of flies. So protected, the meat would not produce maggots and Redi temporarily put to rest the notion of spontaneous generation. His work was one of history’s first experiments in biology.
Although Redi’s work became widely known, the doctrine of spontaneous generation was too firmly entrenched to be abandoned. Science of the 1700s had theological overtones, and some radical philosophers found spontaneous generation to be a useful way of showing that God had no place in creation.
Reports of microorganisms were becoming widespread during that period, and in 1748 a British clergyman named John Needham put forth the notion that in flasks of mutton gravy microorganisms arise by spontaneous generation. Needham even boiled several flasks of gravy and sealed the flasks with corks, as Redi had sealed his jars. Still, the microorganisms appeared. The Royal Society of London was duly impressed and elected Needham to membership.
However, an Italian cleric and scientist, Abbe Lazzaro Spallanzani, criticized Needham’s work. In 1767, Spallanzani boiled meat and vegetable broths for long periods of time and then sealed the necks by melting the glass. As control experiments, he left some flasks open to the air, stoppered some loosely with corks, and boiled some briefly, as Needham had done.
After two days, he found the control flasks swarming with organisms, but the sealed flasks contained none. Spallanzani’s experiment did not settle the issue, though. Needham countered that Spallanzani had destroyed the “vital force” of life with excessive amounts of heat.
Other scientists suggested that the air necessary for life had been excluded. When oxygen was discovered in 1774, Spallanzani’s opponents pointed to this gas as the vital element eliminated.
The controversy on spontaneous generation was no closer to being resolved as the 1800s began. Indeed, resolution would not come until Louis Pasteur’s work in the 1870s. However, the debate focused attention on the fundamental nature of life and encouraged scientists to experiment in biology.
Disease Transmission:
While the doctrine of spontaneous generation was being debated, other scientists were more concerned with how disease was transmitted. As early as 1546, the Italian poet and scientist Girolamo Fracostoro wrote – “Contagion is an infection that passes from one thing to another.” Fracostoro recognized three forms of passage – contact, lifeless objects, and air. His ideas were later interwoven with the miasma theory, and “contagion” came to imply a mechanism by which miasma could be passed to a susceptible person.
The notion that microorganisms were the substance of contagion received little credibility, however. Thus the German priest Athanasius Kircher was paid little attention when in the mid-1600s he reported “microscopic worms” in the blood of plague victims; nor was Christian Fabricius taken seriously in the 1700s when he suggested that fungi might be the cause of rust and smut diseases in plants.
On the contrary, Edward Jenner was accorded many honors in 1798 when he discovered immunization for smallpox, despite the fact that he could not explain the cause of the disease.
By the mid-1800s enough understanding had accumulated to convince physicians that disease could be transmitted among individuals and that the transmission could be interrupted. The works of two investigators, Semmelweis and Snow, intensified this belief.
Ignaz Semmelweis was a Hungarian physician employed by the Vienna Hospital in Austria. In 1847, he reported that the agent of blood poisoning was transmitted to maternity patients by physicians fresh from performing autopsies in the mortuary. Semmelweis showed that hand washing in chlorine water could stop the spread of disease. However, his call for disinfection practices went largely unheeded because it implied that physicians were at fault.
John Snow, a British physician, traced the source of cholera to the municipal water supply of London during an 1854 outbreak. He reasoned that by avoiding the contaminated water source, people could avoid the disease. Snow’s recommendations were adopted, and the spread of disease was halted. In their work, both Semmelweis and Snow also drew attention to the fact that a poison or unseen object in the environment, not a miasma, was responsible for disease. Proof, however, was still lacking.
Term Paper # 6. The Golden Age of Microbiology:
The science of microbiology blossomed during a period of about 60 years referred to as the Golden Age of Microbiology. The period began in 1857 with the work of Louis Pasteur and continued into the twentieth century until the advent of World War I. During these years, numerous branches of microbiology were established and the foundations were laid for the maturing process that has led to modern microbiology.
Louis Pasteur:
In a world ravaged by plague, tuberculosis, typhoid fever, and diphtheria, a large family was often necessary to ensure the next generation. Neither royalty nor common-folk were immune to disease. There were virtually no cures for disease. Indeed, no one was really sure what caused it.
Such were the times in which Louis Pasteur studied at the French school, Ecole Normale Superieure. In 1848, he achieved distinction in organic chemistry for his discovery that tartaric acid a four-carbon organic compound, forms two different types of crystals. Pasteur successfully separated the crystals while looking through a microscope. In doing so, he developed a skill that aided his later studies microorganisms. In 1854, at the age of 32, he was appointed Professor of Chemistry at the University of Lille in northern France.
Pasteur believed that the discoveries of science should have practical applications. He therefore grasped the opportunity in 1857 to try and unravel the mystery of why local wines were turning sour, almost immediately stirring controversy. The prevailing theory held that wine fermentation results from the chemical breakdown of grape juice to alcohol.
No living thing seemed to be involved. But Pasteur’s microscope consistently revealed large numbers of tiny yeast cells overlooked by other scientists. Pasteur believed that yeasts played a major role in fermentation. Moreover, he noticed that sour wines contained populations of barely visible sticks and rods, known to physicians then and now as bacteria.
In a classic series of experiments, Pasteur clarified the role of yeasts in fermentation and showed that bacteria were responsible for sour wine. First he removed all traces of yeast from a sample of grape juice and set the juice aside to ferment. Nothing happened. Next he added yeasts back to the grape juice, and soon the fermentation was proceeding normally. He then found that if he could remove all traces of bacteria from the grape juice, the wine would not turn sour.
Pasteur’s work shook the scientific community. His results demonstrated that yeast cells and bacteria were tiny, living factories where important chemical changes took place. His work also drew attention to microorganisms as the agents of change, because bacteria appeared to make the wine “sick.”
For years, physicians had interpreted bacteria as an effect of disease; that is, they were thought to arise in the body during illness. Pasteur’s work appeared to indicate that they could be a cause of disease, for if they could sour the wine, perhaps they could also make the body ill.
In 1857, Pasteur wrote a short paper on souring by bacteria. In the paper, he implied that microorganisms were related to human illness, and in doing so he set down the foundation for the germ theory of disease. Essentially this theory holds that microorganisms are responsible for infectious diseases.
Pasteur also recommended a practical solution to the sour wine problem. He suggested that grape juice be heated to destroy all the evidence of life, after which yeasts could be added to begin the fermentation. An alternative was to heat the wine before the bacteria soured it. Acceptance of his technique, known as pasteurization, gradually ended the problem. Pasteur’s elation was tempered with sadness, however. In 1859, his daughter Jeanne died of typhoid fever.
Pasteur and Disease:
Pasteur’s interest in microorganisms rose as he learned more about them. He found bacteria in soil, water, air, and the blood of disease victims. Extending his germ theory of disease, he reasoned that if microorganisms were acquired from the environment, their spread could be controlled. If so, perhaps the chain of disease transmission could also be broken.
However, many scientists stubbornly stuck to the notion that bacteria arose spontaneously from organic matter and that disease was inevitable so long as the “life force” was present. Pasteur was therefore drawn into the lingering debate on spontaneous generation, and he sought to discredit the doctrine in order to salvage his own germ theory of disease.
Pasteur first showed that where disease was rampant, the air was full of microorganisms, but where disease was uncommon, the air was clean. He opened flasks of nutrient-laden broth to air from the crowded city, then from the countryside, and next, from a high mountain.
In each succeeding experiment, fewer flasks became contaminated with microorganisms. Still, his critics were vocal. When he boiled broths and showed that they remained free of life, the critics argued that boiling destroyed the “life force” believed to reside in the air.
Finally, in an elegant series of experiments, Pasteur silenced all but the most extreme supporters of spontaneous generation. In the early 1860s, he prepared broth in a series of swan-neck flasks, so named because their S-shaped necks resembled a swan’s. Pasteur boiled the flasks of broth, then left them open to the air and any “life force.”
However, the S-shaped curvature of the neck trapped airborne dust and microorganisms and prevented their entry to the flask. No microorganisms grew in the broth. When the neck was later cut off, however, airborne organisms quickly fell into the broth, and growth appeared within hours.
Pasteur’s work brought to an end the long and tenacious debate on spontaneous generation begun two centuries earlier. By now he was a national celebrity. Once more, however, tragedy entered his life; his daughter Camille developed a tumor and died of blood poisoning in 1865. Pasteur realized that he was no closer to solving the riddle of disease.
That same year, 1865, cholera engulfed Paris, killing 200 people a day. Pasteur attempted to capture the responsible bacterium by filtering the hospital air and trapping the bacteria in cotton. The cotton was then placed in broth medium where a mixture of bacteria grew.
Unfortunately, Pasteur was unable to cultivate one bacterium apart from the others because he was using broth. (In later experiments Koch would use solid culture media instead of broth media.) Although Pasteur demonstrated that bacterial inoculations made animals ill, he could not pinpoint an exact cause. Some of his critics claimed that a poison, or toxin, in the broth was responsible for the disease.
In an effort to help French industry, Pasteur turned his attention to pebrine, the disease of silkworms. Late in 1865, he identified a protozoan infesting the sick silkworms and the mulberry leaves fed to them. Next he separated the healthy silkworms from the diseased silkworms and their food, and he managed to quell the spread of disease.
The achievement strengthened the germ theory of disease. For Pasteur, however, it was another time of grief. Cecille, another of his daughters, died of typhoid fever in 1866. Again he returned to the study of human disease.
Robert Koch:
Although Pasteur failed to relate a specific organism to a specific disease, his work stimulated others to investigate the nature of microorganisms and to ponder their association with disease. For example, Gerhard Hansen, a Norwegian physician, identified bacteria in the tissues of leprosy patients in 1871, and Otto H. F. Obermeier of Germany described bacteria in the blood of relapsing fever patients in 1873.
Another German bacteriologist Ferdinand J. Cohn discovered that bacteria multiply by dividing into two cells. He also observed that certain ones form an extremely resistant structure called the spore. In England, Joseph Lister was sufficiently impressed with Pasteur’s writings on disease to begin applying antiseptics to wound infections.
However, the definitive proof of the germ theory of disease was offered by Robert Koch, a country doctor from East Prussia, now part of Germany. Koch’s primary interest was anthrax, a deadly blood disease in cattle and sheep. Anthrax was a threat to farmers because it ravaged their herds periodically and seemed to reappear time and again in the same district without warning. In 1863 Casimir Davaine, a French physician, had cultivated a bacillus from diseased animals.
Koch was determined to learn more about anthrax. In 1875, in a makeshift laboratory with the blood of diseased sheep and cattle. He then performed meticulous autopsies and noted that the same symptoms appeared regularly.
Next, he isolated a few rod-shaped bacilli from a mouse’s blood by placing the bacilli in the sterile aqueous humor from an ox’s eye. Koch watched for hours as the bacilli multiplied, formed tangled threads, and finally reverted to the resistant spores described by Cohn.
At this point, he took several spores on a sliver of wood and injected them into healthy mice. The symptoms of anthrax appeared within hours. Koch autopsied the animals and found their blood swarming with bacilli. He re-isolated the bacilli in sterile aqueous humor. The cycle was now complete.
Koch communicated his findings to Cohn, and in 1876 Cohn invited the 35year-old physician to present his work at the University of Breslau. Scientists there were astonished. Here was the proof for the germ theory of disease that had eluded Pasteur and for which many of them were waiting. Koch’s procedures came to be known as Koch’s postulates.
These techniques were quickly adopted as a guide for relating specific organisms to specific diseases. They state that the same microorganism must be identified in all cases of the disease, the microorganism must be isolated and grown in pure culture, and the disease must be reproduced in experimental animals inoculated with these pure cultures. The same microorganism must then be recovered. Originally the postulates had been outlined in 1840 by Jakob Henle, a German researcher. One of his students had been Robert Koch.
Pure Culture Techniques:
After the sensation at Breslau subsided, Koch returned to his laboratory and developed numerous staining methods for bacteria. In 1880 he accepted an appointment to the Imperial Health Office, and during this period he happened upon the cultivation techniques that sparked the further development of microbiology.
Koch chanced to observe that a slice of potato contained small masses of bacteria, which he termed colonies. Colonies contained millions of just one kind of bacteria. Koch concluded that bacteria could grow and multiply on solid surfaces, and he added gelatin to his broth to prepare a solid culture medium. He then inoculated bacteria to the surface and set the medium aside to incubate.
Next morning, visible colonies were present on the surface. When colonies of the same bacterium grew together, a pure culture formed. Koch could now inoculate laboratory animals with a pure culture of bacteria and be certain that only one species of bacterium was involved. His work also proved that bacteria, not toxins in the broth, were the cause of disease.
The Competition Period:
At another point in history, Pasteur and Koch might have become friends and colleagues in their mutual search for the agents of disease. However, the years following the 1870 Franco-Prussian war were accompanied by fierce national pride.
Both France and Germany were undergoing unification, and heroes played an important role in the spirit of nationalism. Pasteur became a symbol of French achievement and Koch, his German rival. There sprung up a competition that would last into the next century.
Koch’s proof of the germ theory was presented in 1876. Within two years. Pasteur had verified the proof and gone a step further. He reported that bacteria were temperature-sensitive because chickens did not acquire anthrax at their normal body temperature of 42°C but did so when the animals were cooled down to 37°C.
He also recovered anthrax spores from the soil and pointed out that cattle were probably infected during grazing. This explained the periodic recurrence of the disease. Pasteur suggested that dead animals be burned or buried deeply in soil unfit for grazing.
One of Pasteur’s more remarkable discoveries was made in 1880 when a group of inoculated chickens failed to develop chicken cholera. For months he had been working on ways to enfeeble bacteria using heat, different growth media, passages among animals, and virtually anything he thought might weaken them. Finally, he had developed two cultures whose ability to cause disease was reduced.
The trick, according to his notebooks, was to suspend the bacteria in a mildly acidic medium and allow the culture to remain undisturbed for a long period of time. When it was inoculated to chickens and later followed by a dose of lethal cholera bacilli, the animals did not become sick. This principle is the basis for the use of many vaccines for immunity. Pasteur applied the principle to anthrax in 1881 and found he could protect sheep against the disease.
Pasteur’s experiments put France once more in the forefront of science. However, Koch’s 1881 announcement of pure culture techniques drew attention back to Germany, and within a year Koch isolated the tubercle bacillus, the cause of tuberculosis. In 1884 his associate, Georg Gaffky, cultivated the typhoid bacillus, and that same year another co-worker, Friederich Loeffler, isolated the diphtheria bacillus.
Soon, news was forthcoming from France that Emile Roux and Alexandre Yersin of Pasteur’s group had linked diphtheria to a toxin produced in the body. In later years, Koch’s co-worker, Emil von Behring, successfully treated diphtheria by injecting antitoxin, a blood product (actually a preparation of antibodies) obtained from animals given injections of the toxin. For his work, von Behring was awarded the first Nobel Prize in Physiology or Medicine.
There was also an international flavor in the French and German laboratories. Shibasaburo Kitasato of Japan studied with Koch and successfully cultivated the tetanus bacillus, an organism that grows only in the absence of oxygen. One of Pasteur’s associates was Elie Metchnikoff, a native of the Ukraine.
In 1884, Metchnikoff published an account of phagocytosis, a defensive process in which the body’s white blood cells engulf and destroy microorganisms. This period also witnessed two improvements in microscopy, both attributed to the German physicist Ernst Karl Abbe. In 1878, Abbe introduced the oil immersion lens, a standard feature of modern microscopes.
Eight years later he invented the system of lenses and mirrors known as the Abbe condenser. This apparatus concentrates light on objects being viewed and makes increased magnification feasible. Thus, the improved technology for seeing microorganisms dovetailed the interest in microorganisms.
In 1885, Pasteur reached the zenith of his career when he successfully immunized young Joseph Meister against the dreaded disease rabies. Although he never saw the agent of rabies, Pasteur was able to cultivate it in the brain of animals and inject the boy with bits of the tissue.
Other Pioneers of Microbiology:
With the aging of Pasteur and Koch, a new generation of scientists stepped in to expand their work. For example, a Pasteur Institute scientist, Charles Nicolle, proved that typhus fever was transmitted by lice. Albert Calmette, also of the Institute, developed a harmless strain of the tubercle bacillus used for immunization. Jules Bordet, another French scientist, isolated the bacillus of pertussis (whooping cough) and developed the complement fixation test, a procedure once widely used in the diagnosis of disease.
Koch’s successors included Emil von Behring and Richard Pfeiffer, who isolated one of several organisms that cause meningitis. Still another co-worker was Paul Ehrlich, a chemist who explored the mechanisms of immunity and synthesized the “magic bullet,” an arsenic compound that would seek out and destroy syphilis organisms in the human body.
By the turn of the century, microbiology had moved far beyond the boundaries of France and Germany. Ronald Ross, an English physician working in the Far East, proved that the mosquitoes were the vital link in malaria transmission. The discovery earned him the 1902 Nobel Prize.
Another Englishman, David Bruce, isolated the cause of undulant fever. While working in Africa, Bruce also showed that tsetse flies transmit sleeping sickness. The control of this insect opened the African continent to British colonization. A third British subject, Almroth Wright, described opsonins, the chemical substances that assist phagocytosis in the body. Thirty years later, one of his students, Alexander Fleming, discovered the antibiotic penicillin.
Two Japanese investigators also achieved distinction in these years. In 1897, the Tokyo physician Masaki Ogata reported that rat fleas transmit bubonic plague. This discovery solved a centuries-old mystery of how plague spread. A year later, Kiyoshi Shiga isolated the bacterium that causes bacterial dysentery, an important intestinal disease. The organism was later named Shigella.
The American group of microbiologists was represented by several researchers, among them Daniel E. Salmon and Theobald Smith. These investigators were among the first to use heat-killed bacteria for immunizations. Salmon later studied swine plague and lent his name to Salmonella, the cause of typhoid fever. Smith showed that Texas fever, a disease of cattle, was transmitted by ticks.
In addition, the University of Chicago pathologist Howard Taylor Ricketts located the agent of Rocky Mountain spotted fever in the human bloodstream and demonstrated its transmission via ticks. Another American, William Welch, isolated the gas gangrene bacillus at his laboratory at Johns Hopkins University.
And, Walter Reed led a contingent to Cuba and pinpointed mosquitoes as the insects involved in yellow fever transmission. His discovery led to the mosquito eradication programs that made possible the building of the Panama Canal.
Amid the burgeoning interest in medical microbiology, other scientists devoted their research to the environmental importance of microorganisms. The Russian scientist Sergius Winogradsky, for example, discovered that soil-borne bacteria could bring about chemical changes in ammonia and in iron and sulfur compounds to obtain life-sustaining energy. One of his more significant observations was that certain bacteria utilize carbon dioxide to synthesize carbohydrates, much as plants do in photosynthesis.
Another environmental microbiologist was Martinus Beijerinck, a Dutch investigator. Beijerinck isolated bacteria that could trap nitrogen in the soil and make it available to plants for use in constructing amino acids. He also studied the bacteria prominent in sulfur cycles of the soil and devoted much of his time to the properties of viruses. Together with Winogradsky, he developed many of the laboratory media essential for the study of environmental microbiology.
Term Paper # 7. Types of Microbiology:
The field of microbiology can be generally divided into several sub-disciplines:
1. Microbial Physiology:
The study of how the microbial cell functions biochemically. Includes the study of microbial growth, microbial metabolism and microbial cell structure.
2. Microbial Genetics:
The study of how genes are organised and regulated in microbes in relation to their cellular functions. Closely related to the field of molecular biology.
3. Medical Microbiology:
The study of 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.
4. Veterinary Microbiology:
The study of the role in microbes in veterinary medicine.
5. Environmental Microbiology:
The study of the function and diversity of microbes in their natural environments. Includes the study of microbial ecology, microbially-mediated nutrient cycling, geo-microbiology, microbial diversity and bioremediation.
6. Evolutionary Microbiology:
The study of the evolution of microbes. Includes the study of bacterial systematics and taxonomy.
7. 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.
8. Aero-Microbiology:
The study of Airborne Microorganisms.
9. Food Microbiology:
The study of Microorganisms causing Food Spoilage.
Term Paper # 8. Development of Microbiology:
A microorganism or microbe is an organism that is microscopic (invisible to the naked eye). Microorganisms are often described as single-celled, or unicellular organisms; however, some unicellular protists are visible to the naked eye, and some multicellular species are microscopic.
Microorganisms can be found almost anywhere in the taxonomic organisation of life on the planet. Unicellular organisms carry out all the functions of life. Bacteria and archaea are almost always microscopic, whilst a number of eukaryotes are also microscopic, including most protists and a number of fungi.
Unicellular species are those whose members consist of a single cell throughout their life cycle. This qualification is significant since most multicellular organisms consist of a single cell at the beginning of their life cycles. Unicellular organisms usually contain only a single copy of their genome when not undergoing cell division, although some organisms have multiple cell nuclei.
Microorganisms are found in virtually every habitat present in nature. Even in hostile environments such as the poles, deserts, geysers, rocks, and the deep sea, some types of microorganisms have adapted to the extreme conditions and sustained colonies; these organisms are known as extremophiles.
Some extremophiles have been known to survive for a prolonged time in a vacuum, and some are unusually resistant to radiation. Many types of microorganisms have intimate symbiotic relationships with other larger organisms; some of which are mutually beneficial (mutualism), while others can be damaging to the host organism (parasitism). If microorganisms can cause disease in a host they are known as pathogens.
Microorganisms are used in brewing, baking and other food-making processes. They are also essential tools in biotechnology and the study of biochemistry, genetics and molecular biology. They can also be harmful as a significant cause of human disease, and some have uses as biological weapons.
Microorganisms have an important place in all ecosystems and in most higher-order multicellular organisms (as symbionts). They are vital to the environment, as they participate in the Earth’s element cycles (such as the carbon cycle and nitrogen cycle). They are also involved in the recycling of other organisms’ dead remains (see decomposition) and waste products.
Microbiology is the study of microorganisms, which are unicellular or cell-cluster microscopic organisms. This includes eukaryotes (with a nucleus) such as fungi and protists, and prokaryotes (without a nucleus) such as bacteria, protozoa and viruses (though viruses are not strictly classed as living organisms).
Although much is now known in the field of microbiology, advances are being made regularly. In actual fact, the most common estimates suggest that we have studied only about 1 % of all of the microbes in any given environment.
Thus, despite the fact that over three hundred years have passed since the discovery of microbes, the field of microbiology is clearly in its infancy relative to other biological disciplines such as zoology, botany or even entomology.
Term Paper # 9. Benefits of Microbiology:
While microbes are often viewed negatively due to their association with many human illnesses, 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.
Term Paper # 10. Modern Microbiology
:
Modern microbiology reaches into many fields of humans including the development of pharmaceutical products, the use of quality-control and dairy product production, the control of disease-causing microorganisms in water, and the industrial applications of microorganisms.
Microorganisms are used to produce vitamins, amino acids, enzymes, and growth supplements. They manufacture many foods including fermented dairy products (sour cream, yogurt, and buttermilk), as well as other fermented foods such as pickles, sauerkraut, breads, and alcoholic beverages.
One of the major areas of applied microbiology is biotechnology. In this discipline microorganisms are used as living factories to produce pharmaceuticals that otherwise could not be manufactured.
These substances include the human hormone insulin, the antiviral substance interferon, numerous blood-clotting factors and clot dissolving enzymes, and a number of bacteria can be engineered to increase plant resistance to insects and frost and biotechnology will represent a major application of microorganisms in the next century.