Contributions of Anton van Leeuwenhoek, Joseph Lister, Paul Ehrlich, Edward Jenner, Louis Pasteur, Robert Koch, Martinus W. Beijerinck, Sergei N. Winogradsky, Alexander Fleming, Selman A. Waksman
Anton van
Leeuwenhoek (1632-1723)
Anton van
Leeuwenhoek was a Dutch draper, but spent much of his time constructing simple
microscopes composed of double convex glass lenses held between two silver
plates. His microscopes could magnify
around 50 to 300 times. With these
tools, he was the first to observe and document the world of microbes. Discovery of "Animalcules": In the
1670s, he began sharing his observations with the Royal Society of London. He
described tiny, moving organisms in water, which he called
"animalcules." These were the first recorded observations of bacteria
and protozoa. He also meticulously documented other microscopic life, including
Bacteria in dental plaque and rainwater, Spermatozoa, Blood cells, etc.
Joseph Lister
(1827-1912)
Joseph Lister, a
British surgeon, is known as the "Father of Modern Surgery". Before his
time, post-operative infections often lead to gangrene and sepsis, and were a
major cause of death. Surgeons were unaware that invisible germs were the
source of these infections.
Inspired by Louis
Pasteur's research on fermentation and putrefaction, Lister hypothesized that
microorganisms were responsible for surgical infections. He believed that if
germs could be prevented from entering a wound, infection could be avoided. Lister began using carbolic acid (phenol) as
a disinfectant. This method was introduced in 1867 and it involved a rigorous
antiseptic protocol of Handwashing where
Surgeons and nurses washed their hands with carbolic acid solution, Sterilization
of instruments by soaking in the solution, Wound dressing by bandages and
dressings which were soaked in carbolic acid to prevent airborne bacteria from
entering the wound and adopting an aseptic environment by using a carbolic acid
spray to mist the air in the operating room.
These antiseptic
techniques dramatically reduced the mortality rates associated with surgery.
His work transformed surgery from a dangerous, high-risk procedure into a much
safer and effective medical practice.
Paul Ehrlich
(1854-1915)
Paul Ehrlich was a
German physician and scientist who is considered the "Father of
Chemotherapy". His work bridged the gap between chemistry and medicine,
leading to the development of the first synthetic drugs.
The "Magic
Bullet" Concept: Ehrlich's core idea was to create a "magic
bullet"—a chemical compound that could target and kill a specific
disease-causing organism without harming the host's healthy cells.
In his search for
a treatment for syphilis, Ehrlich and his team synthesized hundreds of
arsenic-based compounds. Their 606th compound, arsphenamine was
marketed as Salvarsan ("the saving arsenic") and became the first
effective cure for syphilis, a previously incurable disease.
Ehrlich also made
significant contributions to immunology. He developed the side-chain theory,
which laid the groundwork for our modern understanding of immune system and he
received the Nobel Prize in Medicine in 1908.
Edward Jenner
(1749-1823)
Edward Jenner was
an English physician known as the "Father of Immunology" for his work
on the smallpox vaccine. Smallpox was a devastating disease with a high
mortality rate and often left survivors with severe scarring.
Jenner observed
that milkmaids who had been infected with cowpox, a much milder disease, seemed
to be immune to smallpox. This led him to the idea that exposure to cowpox
could protect a person from smallpox.
In 1796, Jenner took
pus from a cowpox lesion on the hand of a milkmaid and inoculated it into the
arm of a young boy named James Phipps. The boy developed a mild fever but
quickly recovered. A few weeks later, Jenner inoculated the boy with smallpox
material, but the boy did not get sick.
Jenner's
procedure, which he named vaccination (from the Latin vacca, meaning
"cow"), was published in his 1798 paper, An Inquiry into the
Causes and Effects of the Variolae Vaccinae. This work laid the foundation
for modern immunology and the global campaign that eventually led to the
eradication of smallpox in 1980.
Louis Pasteur
Pasteur is known
as the father of modern microbiology
In 1849 Pasteur
observed that Tartaric acid and racemic acid found in the sediment of
fermenting wine have identical chemical composition. Upon intense inspection using a microscope,
Pasteur noticed that these identical molecules have a different spatial
arrangement. One was the mirror image of the other. This discovery led to the branch of science
known as ‘stereochemistry’.
Until the second
half of the 19th century, Many scientists and philosophers believed in
Spontaneous generation-life could arise spontaneously from non-living matter.
Louis Pasteur disproved Spontaneous Generation and proved that all life comes
from preexisting life. Pasteur
demonstrated that in sterilised and sealed flasks, no life forms develop, and
in sterilised but open flasks, microbes could grow. Microorganisms from the air contaminate
sterile solutions, but air itself does not create microbes.
His studies showed
that living cells, yeast, are responsible for forming alcohol from sugar and
contaminating microorganisms make the fermentation sour
To prevent
contamination, Pasteur heated wine to 50–60 °C, a process now known as pasteurisation.
It is used for the preservation of many foods and beverages, particularly milk
Pebrine, or
"pepper disease," a disease of silkworms, caused by protozoa, mainly Nosema
bombycis and other species. The
silkworm larvae having pebrine are covered in brown dots and are unable to spin
thread. Louis Pasteur identified the
cause and developed a method called ‘graining’ when a plague of the disease
spread across France. Graining enabled
elimination of contaminated females and the preservation of healthy eggs. This technique was adopted by silk producers
throughout the world.
Pasteur identified
that the fermentation process could be arrested by passing air (oxygen) through
the fermenting fluid - known today as the Pasteur effect. He concluded that this is due to a
microorganism that could ferment only in the absence of oxygen. He introduced the terms aerobic and anaerobic
to designate organisms that live in the presence or absence of oxygen
In 1879, Pasteur
worked with the disease fowl cholera, or chicken cholera which was rampant in
chicken coops at the time. When inoculated into a chicken, the bacteria kill
the bird - Pasteurella multocida.
Pasteur used a weakened culture of bacteria to inoculate chickens which
resulted in immune birds and thus the principle of vaccination with attenuated
pathogens was discovered.
In 1879 Pasteur
worked with the disease Anthrax caused by Bacillus anthracis. Anthrax is an infectious disease that affects
cattle, sheep, etc that can be transmitted to man. It was responsible for killing large
populations of sheep in France, detrimental to the economy. Pasteur developed a mild, harmless culture of
anthrax bacteria. Used this culture to vaccinate hundreds of livestock, and
they became immune to the disease.
In anthrax or
chicken cholera vaccination the causative agents are artificially weakened or
attenuated to immunize the animals Pasteur gave these artificially weakened
diseases the generic name of "vaccines", in honour of Jenner's
discovery
In 1882, Pasteur
worked with an epizootic of Swine erysipelas and he developed a vaccine against
this bacterial infection.
He carefully
studied and discovered several other infectious diseases such as those caused
by staphylococcus, streptococcus and pneumococcus.
Pasteur then
worked with rabies. Rabies is a highly
contagious, infectious viral disease that attacks the central nervous system,
transmitted via the bite of rabid animals.
On 1885, Pasteur administered his rabies vaccine on Joseph Meister, a
young man bitten by a rabid dog and saved his life. To help treat future cases of rabies, the
Pasteur Institute was established in 1888 with monetary donations coming from
all over the world.
His medical
discoveries provided direct support for the germ theory of disease and its
application in clinical medicine.
Although Pasteur was not the first to propose the germ theory, his
experiments indicated its correctness.
He is regarded as one of the three main founders of bacteriology,
together with Ferdinand Cohn and Robert Koch
Robert Koch
Robert Koch was a
German physician and microbiologist.
Koch's Postulates:
Koch formulated a set of four criteria, known as Koch's Postulates, to
establish a causal relationship between a specific microorganism and a disease.
These postulates are still used today as a gold standard in microbiology:
1. The
microorganism must be found in abundance in all organisms suffering from the
disease, but not 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 re-isolated from the inoculated, diseased experimental
host and identified as identical to the original specific causative agent.
He
identified the specific causative agents of tuberculosis, cholera, and
anthrax. Robert Koch discovered the
causative agent of Anthrax to be Bacillus
anthracis. He reported the causative agent of the
disease tuberculosis to be the slow-growing Mycobacterium
tuberculosis. Koch studied cholera in Egypt and in India
and identified the causative agent of cholera to be Vibrio cholerae.
Koch
observed the phenomenon of acquired immunity while studying Plasmodium
parasites, the cause of malaria
Koch
cultured bacteria on the sterile surfaces of cut, boiled potatoes, but without
success and tried to solidify regular liquid media by adding gelatin. Gelatin
was not an ideal solidifying agent because it was digested by many bacteria and
melted when the temperature rose above 28°C. Fannie Hesse, the wife of Walther
Hesse, one of Koch’s assistants suggested the use of agar as a solidifying
agent. Agar was not attacked by most bacteria and did not melt until reaching a
temperature of 100°C.
One
of Koch’s assistants, Richard Petri, developed the petri dish (plate), a
container for solid culture media. These developments made possible the
isolation of pure cultures that contained only one type of bacterium.
Koch
also developed media suitable for growing bacteria with meat extracts and
protein digests as nutrient sources and resulted in the development of nutrient
broth and nutrient agar.
For
his research on tuberculosis, Koch received the Nobel Prize in Physiology or
Medicine in 1905. The Robert Koch Institute which monitors public health is
named in his honor and is located in Berlin and Wernigerode
Martinus W. Beijerinck
(1851–1931)
Martinus W. Beijerinck made fundamental contributions
to microbial ecology. He is often considered one of the founders of virology
and environmental microbiology.
He isolated the aerobic
nitrogen fixing bacterium Azotobacter; a root nodule bacterium also capable of
fixing nitrogen (Rhizobium); and sulfate reducing bacteria.
Beijerinck proved that a
virus causes the tobacco mosaic disease
Beijerinck
invented the enrichment culture, a fundamental method of studying microbes from
the environment.
Beijerinckia
(a genus of bacteria), Beijerinckiaceae
(a family of Rhizobiales), and Beijerinck
(crater in moon) are named after him.
Sergei
N. Winogradsky (1856–1953)
The Russian
microbiologist Sergei N. Winogradsky made many contributions to soil
microbiology.
He
discovered that soil bacteria could oxidize iron, sulfur, and ammonia to obtain
energy, and that many bacteria could incorporate CO2 into organic matter much
like photosynthetic organisms do. This is chemoautotrophy or chemosynthesis,
the process by which organisms derive energy from a number of different
inorganic compounds.
Winogradsky
also isolated anaerobic nitrogen-fixing soil bacteria and studied the decomposition
of cellulose.
Winogradsky
discovered the first known form of lithotrophy (using inorganic substrate to
obtain energy via aerobic or anaerobic respiration) during his research with
Beggiatoa in 1887. He reported that Beggiatoa oxidized hydrogen sulfide (H2S)
as an energy source and formed intracellular sulfur droplets.
The
Winogradsky column remains an important display of chemoautotrophy and
microbial ecology. This is a simple
device for culturing a large diversity of microorganisms. the device is a column of pond mud and water
mixed with a carbon source such as newspaper (containing cellulose), egg-shells
(containing calcium carbonate), and a sulfur source such as gypsum (calcium
sulfate) or egg yolk. Incubating the column in sunlight for months will results
in an aerobic/anaerobic gradient as well as a sulfide gradient and promote the
growth of different microorganisms such as bacteria, cyanobacteria, and algae.
Alexander Fleming
(1881 - 1955)
Alexander Fleming
was a Scottish physician and microbiologist.
Discovery of
Penicillin: In 1928, Fleming discovered the first true antibiotic, penicillin.
While studying Staphylococcus bacteria, he noticed that a mold, Penicillium
notatum, had contaminated one of his petri dishes. He observed that the
bacteria colonies around the mold were dying. He correctly identified that the
mold was producing a substance that was killing the bacteria, and he named it
penicillin.
In 1922, Fleming
discovered lysozyme, an enzyme with antibacterial properties found in human
tears, saliva, and other body fluids.
He shared the Nobel
Prize in Physiology or Medicine with Howard Florey and Ernst Chain in 1945.
Selman A. Waksman (1888–1973)
Selman A. Waksman
was a Ukrainian-American biochemist and soil microbiologist.
Waksman and his
team systematically screened thousands of soil microorganisms for antibacterial
properties. In 1943, they isolated streptomycin from the bacterium Streptomyces
griseus. This was the first effective antibiotic against tuberculosis and
other Gram-negative bacterial infections.
Waksman's work
established a methodical approach to finding antimicrobial agents from soil
microbes and lead to the discovery of over a dozen other antibiotics, including
neomycin. He also coined the term "antibiotics" to describe these
substances produced by microorganisms that inhibit the growth of other
microorganisms.
