History of microbiology perfect note

HISTORY OF MICROBIOLOGY

The microscope

i. Zacharias Jansssen

In 1590, Zacharians Janssen developed the first compound microscope in Middleburg,

Holland, Janssen’s microscope consisted of three tubes. One tube served as the outer

casing and contained the other two tubes. At either ends of the inner tubes were lenses

used for magnification. Janssen’s design enabled scientists to enlarge the image of a

specimen three and nine times the specimen’s actual size.

ii. Robert Hooke

In 1665, Robert Hooke, an English scientis, popularized the use of the compound

microscope when he placed lenses over slices of cork and viewed little boxes that he

called cells. It was his discovery that led to the development of cell theory in the

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nineteenth century by Mathias Schleiden. Theoder Schwann, and Rudolf Virchow, Cell

theory states that all living things are composed of cells.

iii. Antoni van Leeuwenhoek

Hooke’s experiments with a crude microscope inspired Antoni van Leenwenhoek to

further explore the micro world. Van Leeuwenhock, an amateur lens grinder, improved

Hooke’s microscope by grinding lenses to achieve magnification. His microscope

required one lens. With his improvement, van Leeuwenhock became the first person to

view a living microorganisms, which he called Animalcules.

This discovery took place during the 1600s, when scientists believed that organisms

generated spontaneously and did not come from another organisms. This sounds

preposterous today; however, back then scientists were just leaning that a cell was the

basic component of an organism.

Origin of Organisms

i. Francesco Redi

In 1668, Italian physician Francesco Redi developed an experiment that demonstrated

that an organisms did not spontaneously appear. He filled jars with rotting meat. Some

jars he sealed and other he left opened. Those that were open eventually contained

maggots, which is the larval stage of the fly. The other jars did not contain maggots

because flies could not enter the jar to lay eggs on the rotting meat.

His critics stated that air was the ingredient required for spontaneous generation of an

organism. Air was absent from the sealed jar and therefore no spontaneous generation

could occur, they said Redi repeated the experiment except this time he placed a screen

over the opened jars. This presented flies from entering the jar. There weren’t any

maggots on the rotting eat.

Until that time scientists did not have a clue about how to fight disease. However, Redi’s

discovery gave scientists an idea. They used Redi’s findings to conclude that killing the

microorganisms that caused a disease could prevent the disease from occurring. A new

microorganisms could only be generated by another microorganisms when it underwent a

reproductive process. Kill that microorganism and you will not have new

microorganisms, the theory went – you could stop the spread of the disease. Scientists

called this the Theory of Biogenesis. The Theory of Biogenesis states that a living cell is

generated from another living cell.

ii. Louis Pasteur

Although the Theory of Biogenesis disproved spontaneous generation, spontaneous

generation was hotly debated among the scientific community until (1861) when Loius

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Pasteur, a French scientific, resolved the issue once and for all. Pasteur showed that

microorganisms were in the air. He proved that sterilized medical instruments became

contaminated once they were exposed to the air.

Pasteur came to this conclusion by boiling beef broth in several short-necked flasks.

Some flasks were left open to cool. Other flasks were sealed after boiling. The opened

flasks became contaminated with microorganisms while no microorganisms appeared in

the closed flasks. Pasteur concluded that airborne microorganisms had contaminated the

opened flaks.

In a follow-up experiment, Pasteur placed beef broth in an open long-necked flask. The

neck was bent into an S-shape. Again he boiled the beef broth and let it cool. The Sshaped

neck trapped the airborne microorganisms.

The beef broth remained uncontaminated even after months of being exposed to the air.

The very same flask containing the original beef broth exists today in Pasteur Institute in

Paris and still shows no sign of contamination. Pasteur’s experiments validated that

microorganisms are not spontaneously generated.

Based on Pasteur’s findings, concerned effort was launched to improve sterilization

techniques to prevent microorganisms from reproducing. Pasteurization, one of the bestknown

sterilization techniques, was developed and named for Pasteur. Pasteurization

kills harmful microorganisms in milk, alcoholic beverages, and other foods and drinks by

heating it enough to kill most bacteria that cause spoilage.

iii. John Tyndall and Ferdinand Cohn

The work of John Tyndall and Ferdinand Cohn in the late 1800s led to one

of the most important discoveries in sterilization. They learned that some

microorganisms are resistant to certain sterilization techniques. Until their

discovery, scientists had assumed that no microorganisms could survive

boiling water, which became a widely accepted method of sterilization. This

was wrong. Some thermophiles resisted heat and could survive a bath in

boiling water. This means that there was not one magic bullet that killed all

harmful microorganisms.

Germ theory

Until the late 1700s, not much was really known about diseases except their impact. It

seemed that anyone who came in contact with an infected person contracted the disease.

A disease that is spread by being exposed to infection is called a contagious disease. The

unknown agent that causes the disease is called a contagion. Today we known that a

contagion is a microorganisms, but in the 1700s many found it hard to believe something

so small could cause such devastation.

i. Rober Koch

see the next post.

ii. Elie Metchnikoff

Elie Metchnikoff, a nineteeth-century Russian zoologist, was interested by Jenner’s work

with vaccinations. Metchnikoff wanted to learn how our bodies react to vaccination by

exploring our body’s immune system. He discovered that white blood cells (leukocytes)

engulf and digest microorganisms that invade the body. He called these cells phagocytes,

which means “cell eating”. “Metchnikoff was one of the first scientists to study the new

area of biology called immunology, the study of the immune system.

Killing the Microorganism

i. Ignaz Semmelwees

Great studies were made during the late 1800s in the development of antiseptic

techniques. It began with a report by Hungarian physician Ignaz Semmelweis on a

dramatic decline in childbirth fever when physicians used antiseptic techniques when

delivering babies. Infections become preventable through the use of antiseptic

techniques.

ii. Joseph Lister

Joseph Lister, an English surgeon, developed one of the most notable antiseptic

techniques. During surgery he sprayed carbolic acid over the patient and then bandged

the patient’s wound with carbolic acid-soaked bandages. Infection following surgery

dramatically dropped when compared with surgery performed without spraying carbolic

acid. Carbolic acid, also known as phenol was one of the first surgical antiseptic.

iii. Paul Ehrlich

Antiseptics prevented microorganisms from infecting a person, but scientists still needed

a way to kill microorganisms after they infected the body. Scientists needed a magic

bullet that cured diseases. At the turned of the nineteeth century, Paul Ehrlich, a German

chemist, discovered the magic bullet. Ehrich blended chemical elements into a

convocation that, when inserted into an infected area, killed microorganisms without

affecting the patient. Today we call Ehrlich’s concoction a drug. Ehrlic’s innovation

has led to chemotherapy using drugs that are produced by chemical synthesis.

iv. Alexander Fleming

Scientists from all over set out to use Ehrlich’s findings to find drugs that could make

infected patients well again. One of the most striking breakthroughs came in 1929 when

Alexander Fleming discovered Penicillin snotatum, the organism that synthesizes

penicillin. Penicillium notatum is a fungus that kills the Staphyloccus aureus

microorganism and similar microorganisms.

Fleming grew cultures of Staphyloccus aureus, a bacterium, in the laboratory. He was

also conducting experiments with Penicillium notatum, a mold. By accident the

Staphyloccous aureus was contaminated with the Penicillium notatum, causing the

Staphyloccocus to stop reproducing and die. Penicillium notatum became one of the first

antibiotic. An antibiotic is a substance that kills bacteria.