History of Microbiology

Babylonians were using yeast to make beer over 8000 years ago and acetic acid bacteria to make vinegar over 6000 years ago. About 5000 years ago, Persia (now Iran) region recorded the wine-making.

The Romans had God for that were specific for microorganisms. The roman God of mold and mildew was “Robigus” and “Robigo” which means crop rust. (Rust is one of the plant diseases caused by a fungus). God Robigus was very much feared because of crop loss.

About 2000 years ago, Romans proposed that diseases were caused by tiny animals. But fundamentalist religions had a stronghold over the progress. The real microbiology history starts from the 1600s when people began to make crude lenses and microscopes.

The earliest microscopic observations appear to have been made between 1625 and 1630 on bees and weevils by the Italian Francesco Stelluti, using a microscope probably supplied by Galileo.

In 1665 the first drawing of a microorganism was published in Robert Hooke’s Micrographia.

However, the first person to publish extensive, accurate observations of microorganisms was the amateur microscopist Antony van Leeuwenhoek (1632–1723) of Delft, the Netherlands. Leeuwenhoek earned his living as a draper and haberdasher (a dealer in men’s clothing and accessories) but spent much of his spare time constructing simple microscopes composed of double convex glass lenses held between two silver plates His microscopes could magnify around 50 to 300 times, and he may have illuminated his liquid specimens by placing them between two pieces of glass and shining light on them at a 45° angle to the specimen plane. This would have provided a form of dark-field illumination in which the organisms appeared as bright objects against a dark background and made bacteria clearly visible. Beginning in 1673, Leeuwenhoek sent detailed letters describing his discoveries to the Royal Society of London. It is clear from his descriptions that he saw both prokaryotes and protozoa.

Edward Jenner is credited with the first vaccine – in epidemics of smallpox during the late 1700’s he observed that milkmaids didn’t get the disease, cattle had a similar disease – cowpox, milkmaids had cowpox lesions, but not smallpox, he purposefully took scrapings from a cowpox blister and scraped an 8-year- old volunteer. With the material – child got mild illness but not smallpox, Vaccination comes from Latin word “Vacca” meaning cow. Jenner laid the foundation for Pasteur’s later work with other vaccinations. (Vaccinia virus similar to Variola smallpox virus, today a possible bioterror weapon – genetically engineered variola?)

Louis Pasteur (1822 – 1895) and disproval of Spontaneous generation theory

He performed a “gooseneck experiment”. The nutrient of the flask was heated and the untreated – unfiltered air could pass in or out, but the germs settled in the gooseneck and no microbes were observed in the nutrient solution.

His concept of Germs theory of disease (which means germs are responsible for the disease, not the inert mater) ends the SG theory.

Contributions of Louis Pasteur (1822 – 1895)

• Disproved the SG theory

• Discovered that fermenting fruit to alcohol by microbes – From now the Fermentation started

• Sorted different microbes giving a different taste of wine.

• He selected a particular strain (Yeast) for high-quality wine.

• He developed a method to remove the undesired microbes from juice without affecting its quality. Heating the juice at 62.8°C for half an hour did the job. This technique is called Pasteurization, which is commonly used in the field of the milk industry.

• He discovered that parasites (protozoa) causing the pebrine disease of silkworms. He suggested that disease-free caterpillars can eliminate the disease.

• He isolated anthrax-causing bacilli from the blood of cattle, sheep, and human beings.

• He also demonstrated the virulence (the ability of a microbe to cause disease) of bacteria

• He developed a vaccine (a killed or attenuated microbe to induce the immunity) against rabbis from the brains and spinal cord of the rabbit

John Tyndall (1820 -1893)

• Proved that dust carries the germs and if no dust in the air, the sterile broth remained free of microbial growth for an indefinite period.

• He also developed a sterilization method “Tyndallization”, referred to as intermittent or fractional sterilization. The subsequent cooling and heating by steam for 3 days will remove the germs and their spores.

Martinus Willium Beijerinck (1851 – 1931)

• Developed the enrichment technique to isolate various groups of bacteria.

• Isolated sulfur-reducing bacteria and sulfur-oxidizing bacteria from soil

• Isolated free-living nitrogen-fixing bacterium, Azotobacter from the soil,

• Root nodulating bacterium Rhizobium, Lactobacillus, green algae were identified by him

• He confirmed the Tobacco mosaic virus causes disease and is incorporated into the host plant to reproduce.

Sergei Winogradsky (1856 – 1953)

The following are the contributions of Winogradsky to soil microbiology.

• Microorganisms involved in N cycle, C cycle, S cycle

• Nitrification process in soil

• Autotrophic nutrition of bacteria

• Chemolithotrophic nutrition of soil bacteria

• Discovered anaerobic nitrogen-fixing bacterium Clostridium pasteurianum

Walther Hesse & Fannie E. Hesse (1883)

• They used agar instead of gelatin for the preparation of media. Agar goes to a solution at 100°C and solidifies at 45°C. Till now this was not replaced by any other substance.

Joseph Lister (1878)

• Developed Pure culture technique. A pure culture is referred to as the growth of mass of cells of the same species in a vessel. He developed the pure cultures of bacteria using the serial dilution technique.

• He also discovered that carbolic acid disinfects the surgical equipment and dressings leads the reduction of post-operational deaths/infections.

Alexander Fleming (1928) identified Penicillium notatum inhibiting Staphylococcus aureus and identified the antibiotic Penicillin

• 1929-Discovered antibiotic penicillin –an important milestone in medical microbiology

• Found that natural substances having antimicrobial activity- Saliva, Nasal mucous

• Worked on Staphylococcus aureus,-inhibition of growth-due to Penicillin

• Florey & Chain-isolated Penicillin in pure culture.

Selman A. Waksman, 1945 identified Streptomycin antibiotic from a soil bacterium. He also coined the term antibiotics (referring to a chemical substance of microbial origin which is in small quantity exert antimicrobial activity.

• 1927- Wrote the book on Principles of soil Microbiology

• In 1939 Waksman and his colleagues undertook a systematic effort to identify soil organisms producing soluble substances that might be useful in the control of infectious diseases, what is now known as antibiotics

• Within a decade ten antibiotics were isolated and characterized,

• three of them with important clinical applications

• actinomycin in 1940, streptomycin in 1944, and neomycin in 1949.

• Eighteen antibiotics were discovered under his general direction.

SPONTANEOUS GENERATION THEORY

From earliest times, people had believed in spontaneous generation —that living organisms could develop from non-living matter.

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation or Abiogenesis, the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water.

This theory persisted into the seventeenth century when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain molded, mice appeared. Jan Baptista van Helmont, a seventeenth-century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

This view finally was challenged by the Italian physician, Francesco Redi (1626–1697), who carried out a series of experiments on decaying meat and its ability to produce maggots spontaneously. Redi placed meat in three containers. One was uncovered, a second was covered with paper, and the third was covered with fine gauze that would exclude flies. Flies laid their eggs on the uncovered meat and maggots developed. The other two pieces of meat did not produce maggots spontaneously. However, flies were attracted to the gauze-covered container and laid their eggs on the gauze; these eggs produced maggots. Thus, the generation of maggots by decaying meat resulted from the presence of fly eggs, and meat did not spontaneously generate maggots as previously believed. Similar experiments by others helped discredit the theory for larger organisms.

Leeuwenhoek’s discovery of microorganisms renewed the controversy. Some proposed that microorganisms arose by spontaneous generation even though larger organisms did not. They pointed out that boiled extracts of hay or meat gave rise to microorganisms after sitting for a while.

In 1748 the English priest John Needham (1713–1781) reported the results of his experiments on spontaneous generation. Needham boiled mutton broth in flasks that he then tightly stoppered. Eventually many of the fl asks became cloudy and contained microorganisms. He thought organic matter contained a vital force that could confer the properties of life on non-living matter.

A few years later, the Italian priest and naturalist Lazzaro Spallanzani (1729–1799) improved on Needham’s experimental design by first sealing glass fl asks that contained water and seeds. If the sealed flasks were placed in boiling water for three-quarters of an hour, no growth took place as long as the fl asks remained sealed. He proposed that air carried germs to the culture medium but also commented that the external air might be required for growth of animals already in the medium.

The supporters of spontaneous generation maintained that heating the air in sealed flasks destroyed its ability to support life.

Several investigators attempted to counter such arguments. Theodore Schwann (1810–1882) allowed air to enter a flask containing a sterile nutrient solution after the air had passed through a red-hot tube. The flask remained sterile. Subsequently, Georg Friedrich Schroder (1810–1885) and Theodor von Dutch (1824–1890) allowed air to enter a flask of the heat-sterilized medium after it had passed through sterile cotton wool. No growth occurred in the medium even though the air had not been heated.

Despite these experiments, the French naturalist Felix Pouchet (1800–1872) claimed in 1859 to have carried out experiments conclusively proving that microbial growth could occur without air contamination. This claim provoked Louis Pasteur (1822–1895) to settle the matter.

Pasteur first filtered air through cotton and found that objects resembling plant spores had been trapped. If a piece of the cotton was placed in sterile medium after air had been filtered through it, microbial growth occurred. Next, he placed nutrient solutions in flasks, heated their necks in a flame, and drew them out into a variety of curves. The swan neck flasks that he produced in this way had necks open to the atmosphere. Pasteur then boiled the solutions for a few minutes and allowed them to cool. No growth took place even though the contents of the fl ask were exposed to the air. Pasteur pointed out that no growth occurred because dust and germs had been trapped on the walls of the curved necks. If the necks were broken, growth commenced immediately. Pasteur had not only resolved the controversy by 1861 but also had shown how to keep solutions sterile.

The English physicist John Tyndall (1820–1893) and the German botanist Ferdinand Cohn (1828–1898) dealt a final blow to spontaneous generation. In 1877 Tyndall demonstrated that dust did indeed carry germs and that if dust was absent, broth remained sterile even if directly exposed to air. During the course of his studies, Tyndall provided evidence for the existence of exceptionally heat-resistant forms of bacteria. Working independently, Cohn discovered that the heat-resistant bacteria recognized by Tyndall were species capable of producing bacterial endospores. Cohn later played an instrumental role in establishing a classification system for prokaryotes based on their morphology and physiology.