HISTORY AND DEVELOPMENTS OF MICROBIOLOGY

 Pre-17th Century to Late 17th Century:

For centuries, people speculated about invisible entities causing disease and decay. Girolamo Fracastoro, an Italian scholar in the mid-1500s, proposed that contagion was an infection passed by "seed-like entities."

Robert Hooke (1665): Made the first recorded microscopic observation of the fruiting bodies of molds, describing what he called "cells" in plant tissues.

Antonie van Leeuwenhoek (1670s): called the "Father of Microbiology," Leeuwenhoek, a Dutch draper, perfected his own simple, single-lens microscopes. He was the first to accurately observe and describe a wide range of microorganisms, which he called "animalcules,". His meticulous documentation and drawings sent to the British Royal Society provided the first concrete evidence of a microscopic world.

Francesco Redi (mid-17th century): Through experiments with decaying meat, he showed that maggots did not spontaneously generate but came from flies.

18th - 19th Centuries:

Lazzaro Spallanzani (late 18th century): Demonstrated that boiling broth would sterilize it and prevent microbial growth if kept sealed from the air, further challenging spontaneous generation.

Louis Pasteur (mid-19th century): performed his famous "swan-necked flask" experiments. He showed that airborne microbes, not spontaneous generation, were responsible for contaminating sterilized broths.

Germ Theory of Disease:

Louis Pasteur: Pasteur made seminal discoveries in vaccination (anthrax, rabies) and food safety (pasteurization).

Joseph Lister (mid-19th century): Applying Pasteur's findings, this English surgeon introduced antiseptic surgical procedures using carbolic acid, drastically reducing post-operative infections and mortality. He is considered the "Father of Antiseptic Surgery."

Robert Koch (late 19th century): A German physician, Koch perfected bacteriological techniques, including staining and solid media isolation (using gelatin, then agar). He established a systematic approach to proving that specific microbes cause specific diseases, known as Koch's Postulates.

Late 19th Century - Present:

Ferdinand Cohn (19th century): A botanist, he laid foundational work in bacteriology, classifying bacteria and discovering bacterial spores.

Fanny Hesse (late 19th century): Developed the use of agar as a solidifying agent for culture media, revolutionizing the isolation and study of pure bacterial cultures.

Richard J. Petri (late 19th century): Developed the Petri dish, an essential tool for culturing microorganisms.

Martinus Beijerinck and Sergei Winogradsky (late 19th century): Considered the founders of general microbiology, they revealed the true breadth of microbial diversity and their ecological roles.

Edward Jenner (late 18th century): Developed vaccination techniques against smallpox.

Paul Ehrlich (early 20th century): Contributed significantly to chemotherapy, searching for "magic bullets" that could kill microbes without harming the host.

Alexander Fleming (1928): Discovered penicillin, the first widely used antibiotic, ushering in the era of antimicrobial therapy.

spontaneous generation:

Spontaneous generation was a long-held, now-disproven, scientific theory that posited living organisms could arise from non-living matter.

• The core belief was that certain conditions could cause life to spontaneously emerge from inanimate objects.

The main observations were of 

• Maggots appearing on decaying meat.
• Mice seemingly appearing from dirty rags and grains.
• Frogs emerging from mud.
• Microorganisms appearing in spoiled broth.

Some proponents, like Aristotle, believed that non-living matter contained a "pneuma" or "vital heat" that, under the right circumstances, could imbue it with life.

 Controversy and Disproval:

Francesco Redi (17th Century):

• Redi challenged the idea that maggots spontaneously arose from meat. He set up three jars with meat: one open, one sealed, and one covered with fine mesh.
• Maggots only appeared in the open jar, where flies could lay eggs. No maggots appeared in the sealed jar, and maggots appeared on the mesh (but not the meat) in the mesh-covered jar, showing that flies were necessary for maggot production.
• This experiment provided strong evidence against spontaneous generation for larger organisms.

Lazzaro Spallanzani (18th Century):

• Spallanzani boiled broth in sealed flasks and unsealed flasks.
• The broth in the sealed flasks remained clear (no microbial growth), while the unsealed flasks became cloudy with microorganisms.
• that microbes did not spontaneously generate but came from the air. However, critics argued that boiling had destroyed a "vital force" in the air, preventing spontaneous generation in the sealed flasks.

Louis Pasteur (19th Century):

• Pasteur conducted his famous "swan-necked flask" experiment. He boiled broth in flasks with long, S-shaped necks that allowed air to enter but trapped airborne dust particles and microbes in the curves of the neck.
• The broth in the swan-necked flasks remained sterile for long periods because microbes could not reach it. If the neck was broken, allowing dust and microbes to enter, the broth quickly became contaminated.
• Pasteur's elegant experiment conclusively disproved spontaneous generation for microorganisms. He demonstrated that "life only comes from life" (biogenesis).

Germ theory of disease:

It states that many diseases are caused by microorganisms, too small to be seen with the naked eye, which invade the body and disrupt its normal functions. These microorganisms, often referred to as "germs," include bacteria, viruses, fungi, protozoa, and other pathogens.

Beliefs before germ theory:

1. The prevailing theory for centuries, it held that diseases like cholera or the Black Death were caused by "miasma" – a noxious, invisible vapor emanating from rotting organic matter or "bad air."
2. Diseases were often attributed to divine punishment, evil spirits, or imbalances of the body's humors.
3. The belief that living organisms, including disease-causing ones, could spontaneously arise from non-living matter

Main contributors towards germ theory:

Louis Pasteur (French Chemist and Microbiologist):

• His famous swan-necked flask experiments conclusively showed that microbes do not spontaneously arise in sterile broths but come from pre-existing microbes in the air.
• He demonstrated that specific microorganisms were responsible for specific types of fermentation (e.g., yeast for alcohol, bacteria for souring wine).
• He showed that a microscopic organism caused a devastating silkworm disease.
• His development of vaccines for anthrax and rabies.

Joseph Lister (English Surgeon):

• Inspired by Pasteur's work on airborne microbes, Lister realized that microorganisms were responsible for surgical wound infections.
• He pioneered the use of carbolic acid (phenol) to sterilize surgical instruments, dressings, and even the air in the operating room.

Robert Koch (German Physician):

Koch postulates:

1. The microorganism must be found in abundance in all organisms suffering from the disease but should not be found in healthy organisms.
2. The microorganism must be isolated from a diseased organism and grown in a pure culture.
3. The cultured microorganism should cause disease when introduced into a healthy organism.
4. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

Cell theory:

 It states that all living organisms are composed of cells, and that cells are the basic units of structure and function in all living things.

 Historical Foundation and Development:

17th Century:

•  Hooke used an early compound microscope, observed thin slices of cork and saw tiny, box-like compartments, which he called "cells" because they reminded him of the small rooms in a monastery. 
• Leeuwenhoek developed more powerful simple microscopes, he was the first to observe and describe living cells, including bacteria and protozoa, which he called "animalcules," in various samples like pond water, blood, and dental plaque.

18th century:

• A German botanist, Schleiden concluded after extensive observations that all plants are composed of cells.
• A German zoologist, building on Schleiden's work and his own observations of animal tissues, concluded that all animals are also composed of cells and also proposed that cells are the basic units of life for both plants and animals.
• A German physician, Virchow famously stated "Omnis cellula e cellula", which means "all cells arise from pre-existing cells."

Modern cell theory:

1. Energy flow (metabolism and biochemistry) occurs within cells.
2. Cells contain hereditary information (DNA) which is passed from cell to cell during cell division.
3. All cells are basically the same in chemical composition in organisms of similar species.
4. The activity of an organism depends on the total activity of independent cells.