A. Definition: Microbiology
Microbiology is a
branch of biology, it is the study of
microorganisms. It can be defined as the biology of microscopic organisms as the microorganisms in microbiology visible only under
a microscope. Microbiology covers several
disciplines, including virology (study of viruses), bacteriology (study of
bacteria), mycology (study of fungi) and parasitology (study of parasites).
Each of these disciplines may include but is not limited
to studies of infectious disease-causing microorganisms only. For example,
specialties within microbiology may include microbial physiology (i.e.,
microbial growth, metabolism, structure), microbial genetics and evolution,
environmental microbiology (i.e., microbial ecology), industrial microbiology
(i.e., industrial fermentation, wastewater treatment) and food microbiology
(i.e., use of microbes for food production, fermentation).
Microorganisms are
widespread in the nature. Some bacteria inhabit the inner and outer surfaces of
the human body and these are non-pathogenic micro-organisms as they produced no
disease. The bacteria of the small and large intestine are even useful
digestive aid since it provides among other things important for blood clotting
vitamin K. Such a union between two organisms is called symbiosis.
There are microorganisms
that act cause disease and are therefore pathogenic, for example the causative
agent of bacterial infection and viral diseases. Living beings that live at the
expense of another organism are called a parasite such as arthropods and worms.
B. Classification of microbiology
1. Bacteria are unicellular
organisms, they come in many shapes and sizes and are either a parasite or live independently. Common shapes are rod-shaped (bacillus), sphere-shaped (coccus) and helix-shaped (spirilla). These shapes are caused by
the growth of the cell wall of the bacterium. Bacteria multiply in a
straightforward manner which each single celled bacterium grows until there is
enough material to form two separate bacteria. The one parent bacterium then splits into 2 progeny bacteria. Many
bacteria can actively move through small appendages (flagella). There are 2
types of bacteria, aerobic bacteria which need oxygen to live and anaerobic
bacteria that live without oxygen. Antibiotics can
usually kill them. An example of bacteria is meningitis and pneumonia.
2. Viruses are microscopically small and are the simplest
microbiological entity. A virus is not an independent living
organism and needs a host cell to replicate. They are sub-microscopic parasitic
particles of nucleic acid (RNA or DNA) that are wrapped
in protein. It has no cell structure but rather consist
of a protein coat (capsid), nucleic acids, which contain the genetic
information and possibly a case. Viruses can reproduce only by using living
cells. They penetrate to it with their nucleic acids into cells and alter cell
metabolism so that it forms new viruses - so call this kind cell parasites. The
affected cells are called the host cells, they perish in consequence of virus
infection in the rule. Viruses are immune to antibiotics and are spread in the
air or by direct contact. They can lead to serious or sometimes deadly diseases
such as AIDS.
3. Mushrooms (fungi) as the plants have a rigid cell
wall, a nucleus and are motile but has no chlorophyll so
they are not capable of photosynthesis which means they cannot use light to
build energy-rich compounds. Fungi reproduce by spores and are about ten times
larger than bacteria. They live by absorbing certain nutrients from any organic matter. There are over 120,000 different species of
fungi that cause of which about 100 human diseases. Fungal infections commonly
indicate a defensive weakness of the patient. Penicillin is made from a fungus.
4. Protozoa is a single celled organism which is able to
move and will feed on any organic compound of carbon and nitrogen, for example
an amoeba. They has an identifiable nucleus and can be parasites or live
independently. They are usually found in water or soil. Protozoa have different
shapes and will produce asexually. They can inhabit the human body for example
in the large intestine as a parasite.
5. Algae are photosynthetic organisms of a group which
live mostly in water. It includes the different seaweeds. Algae are different
to plants because they have no true stems, roots or leaves. Algae also cause
red tide, which can be fatal to fish and people eating contaminated shellfish.
They will reproduce asexually.
C. History of Microbiology
1. Antonie van Leeuwenhoek
(1632 – 1723)
Antonie van Leeuwenhoek was born in Delft on 24 October 1632. In 1648,
van Leeuwenhoek was apprenticed to a textile merchant, which is where he
probably first encountered magnifying glasses, which were used in the textile
trade to count thread densities for quality control purposes. Aged 20, he
returned to Delft and set himself up as a linen-draper. He prospered and was
appointed chamberlain to the sheriffs of Delft in 1660, and becoming a surveyor
nine years later.
In 1668, van Leeuwenhoek paid his first and only visit to London, where
he probably saw a copy of Robert Hooke's 'Micrographia' (1665) which included
pictures of textiles that would have been of interest to him. In 1673, he
reported his first observations - bee mouthparts and stings, a human louse and
a fungus - to the Royal Society. He was elected a member of the society in 1680
and continued his association for the rest of his life by correspondence.
In 1676, van Leeuwenhoek observed water closely and was surprised to see
tiny organisms - the first bacteria observed by man. His letter announcing this
discovery caused widespread doubt at the Royal Society but Robert Hooke later
repeated the experiment and was able to confirm his discoveries.
As well as being the father of microbiology, van Leeuwenhoek laid the
foundations of plant anatomy and became an expert on animal reproduction. He
discovered blood cells and microscopic nematodes and studied the structure of
wood and crystals. He also made over 500 microscopes to view specific objects.
He also discovered sperm, which he considered one of the most important
discoveries of his career and described the spermatozoa from molluscs, fish,
amphibians, birds and mammals, coming to the novel conclusion that
fertilisation occurred when the spermatozoa penetrated the egg. Van Leeuwenhoek
died on 30 August 1723.
2. Edward Jenner (1749 –
1823)
Edward Jenner was born in Berkeley, Gloucestershire on 17 May 1749, the
son of the local vicar. At the age of 14, he was apprenticed to a local surgeon
and then trained in London. In 1772, he returned to Berkeley and spent most the
rest of his career as a doctor in his native town.
In 1796, he carried out his now famous experiment on eight-year-old
James Phipps. Jenner inserted pus taken from a cowpox pustule and inserted it
into an incision on the boy's arm. He was testing his theory, drawn from the
folklore of the countryside, that milkmaids who suffered the mild disease of
cowpox never contracted smallpox, one of the greatest killers of the period,
particularly among children. Jenner subsequently proved that having been
inoculated with cowpox Phipps was immune to smallpox. He submitted a paper to
the Royal Society in 1797 describing his experiment, but was told that his
ideas were too revolutionary and that he needed more proof. Undaunted, Jenner
experimented on several other children, including his own 11-month-old son. In
1798, the results were finally published and Jenner coined the word vaccine
from the Latin 'vacca' for cow.
Jenner was
widely ridiculed. Critics, especially the clergy, claimed it was repulsive and
ungodly to inocculate someone with material from a diseased animal. A satirical
cartoon of 1802 showed people who had been vaccinated sprouting cow's heads.
But the obvious advantages of vaccination and the protection it provided won
out and vaccination soon became widespread. Jenner became famous and now spent
much of his time researching and advising on developments in his vaccine.
Jenner carried out research in a number of other areas of medicine and was also
keen on fossil collecting and horticulture. He died on 26 January 1823.
Louis Pasteur was born on 27 December 1822 in Dole in the Jura region of
France. His father was a tanner. In 1847, he earned a doctorate from the École
Normale in Paris. After several years of research and teaching in Dijon and
Strasbourg, in 1854, Pasteur was appointed professor of chemistry at the
University of Lille. Part of the remit of the faculty of sciences was to find
solutions to the practical problems of local industries, particularly the
manufacture of alcoholic drinks. He was able to demonstrate that organisms such
as bacteria were responsible for souring wine and beer (he later extended his studies
to prove that milk was the same) and that the bacteria could be removed by
boiling and then cooling the liquid. This process is now called pasteurisation.
Pasteur then undertook experiments to find where these bacteria came
from and was able to prove that they were introduced from the environment. This
was disputed by scientists who believed they could spontaneously generate. In
1864, the French Academy of Sciences accepted Pasteur's results. By 1865,
Pasteur was director of scientific studies at the École Normale, where he had
studied. He was asked to help the silk industry in southern France, where there
was an epidemic amongst the silkworms. With no experience of the subject,
Pasteur identified parasitic infections as the cause and advocated that only
disease-free eggs should be selected. The industry was saved.
Pasteur's
various investigations convinced him of the rightness of the germ theory of
disease, which holds that germs attack the body from outside. Many felt that
such tiny organisms as germs could not possibly kill larger ones such as
humans. Pasteur now extended this theory to explain the causes of many diseases
- including anthrax, cholera, TB and smallpox - and their prevention by
vaccination. He is best known for his work on the development of vaccines for
rabies. In 1888, a special institute was founded in Paris for the treatment of
diseases. It became known as the Institute Pasteur. Pasteur was its director
until his death on 28 September 1895. He was a national hero and was given a
state funeral.
4. Joseph Lister (1827 –
1912)
Joseph Lister did not discover a new
drug but he did make the like between lack of cleanliness in hospitals and deaths
after operations. Lister was born in 1827 and died in 1912. As Professor of
Surgery at Glasgow University, he was very aware that many people survived the
trauma of an operation but died afterwards of what was known as ‘ward fever’.
Work on ward cleanliness and the link
between germs and good post-operative health had already been studied by a
Hungarian doctor called Ignaz Semmelweiss. He argued that if a doctor went from
one patient to another after doing surgery, that doctor would pass on to the next
visited patient a potentially life threatening disease. He insisted that those
doctors who worked for him wash their hands in calcium chloride after an
operation and before visiting a new patient.
Deaths on the wards Semmelweiss was in
charge of fell from 12% to just 1%. But despite this, he came up against the
conservatism of those who dominated Hungarian medicine and his findings were
ignored. Semmelweiss died in 1865 of blood poisoning.
In 1865, Lister read about the work
done by Louis Pasteur on how wine was soured. Lister believed that it was
microbes carried in the air that caused diseases to be spread in wards. People
who had been operated on were especially vulnerable as their bodies were weak
and their skin had been cut open so that germs could get into the body with
more ease.
Lister decided that the wound itself
had to be thoroughly cleaned. He then covered the wound with a piece of lint
covered in carbolic acid. He used this treatment on patients who had a compound
fracture. This is where the broken bone had penetrated the skin thus leaving a
wound that was open to germs. Death by gangrene was common after such an
accident. Lister covered the wound made with lint soaked in carbolic acid. His
success rate for survival was very high.
Lister then developed his idea further
by devising a machine that pumped out a fine mist of carbolic acid into the air
around an operation. The number of patients operated on by Lister who died fell
dramatically.
5. Robert Koch (1843 – 1910)
Robert Koch was born in 1843. Koch
worked on anthrax and tuberculosis (TB) and he further developed the work of Louis Pasteur. Koch came from a poor mining family and it took him a
lot of determination to get a university place where he first studied
mathematics and natural science and then studied medicine.
Pasteur was convinced that microbes caused diseases in humans but his work
on cholera had failed. He was never able to directly link one microbe with a
disease but Koch succeeded in doing this.
Koch was a doctor and he had a detailed knowledge of the human body –
something that Pasteur, as a research scientist – lacked. He was also skilled
in experiments, the result of his work in natural sciences. Qualities that also
proved to be important were his ability to work for long periods of time and his
patience. However, Koch was also difficult to work with and could not tolerate
anyone telling him that his theories were wrong.
In 1872, Koch became district medical officer for a rural area near Berlin.
He started to experiment with microbes in a small laboratory he had built for
himself in his surgery. The first disease that Koch investigated was anthrax. This was a disease
that could seriously affect herds of farm animals and farmers were rightly in
fear of it. Other scientists had also been working on anthrax. In 1868, a
French scientist called Davaine had proved that a healthy animal that did not
have anthrax could get the disease if it was injected with blood containing
anthrax. Koch developed this work further and for three years he spent all his
spare time finding out what he could about the disease, including its life
cycle.
Koch found out that the anthrax microbe produced spores that lived for a
long time after an animal had died. He also proved that these spores could then
develop into the anthrax germ and could infect other animals. After this, Koch moved onto germs that specifically affected humans. In
1878, he identified the germ that caused blood poisoning and septicemia. He
also developed new techniques for conducting experiments that influenced the
way many other scientists carried out their experiments. He knew that infected
blood contained the septicemia germ but he could not see these germs under a
microscope, and therefore other scientists were unlikely to believe what he
thought to be true without the evidence.
Koch discovered that methyl violet dye showed up the septicemia germ under
a microscope by staining it. He also photographed the germs so that people
outside of his laboratory could see them.
Koch also devised a method of proving which germ caused an infection. His
work was rewarded in 1880 when he was appointed to a post at the Imperial
Health Office in Berlin. Here, Koch perfected the technique of growing pure
cultures of germs using a mix of potatoes and gelatin. This was a solid enough
substance to allow for the germs to be studied better. Koch gathered round him
a team of researchers in Berlin in 1881 and began to work on one of the worst
diseases of the nineteenth century – tuberculosis (TB).
The TB germ was much smaller than the anthrax germ so the search for it was
difficult. Using a more specialized version of his dye technique, Koch and his
team searched for the TB germ. In May 1882, Koch announced that his team had
found the germ. His announcement caused great excitement. It also generated
what became known as ‘microbe hunters’ – a new generation of young scientists
who were inspired by the work of both Koch and Pasteur. One of those who was
inspired by Koch was Paul Ehrlich.
What was Koch’s legacy? He had finally laid to rest the belief that ‘bad
air’ caused disease. He had inspired many other younger researchers to build on
his work. He had found the germs of two feared diseases– anthrax and TB. He had
developed research techniques that others could use throughout the world. By 1900, twenty-one germs that caused diseases had been identified in just
21 years. "As soon as the right method was found, discoveries came as
easily as ripe apples from a tree." (Koch) It was Koch who had developed
the right methods.
6. Paul Ehrlich (1854 – 1915)
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTBJVdQHz9GojQOmG5fUZnJrxpf-azh_hTi9rdO_0BAr1Rz8y7BH9IGAOcEZMNk-bSnwst7xjXFgScFS5RXT63bIPyCFM_my-mVjUp_CAcn63ylzVQ8zEp_RQb4j0n42x38Mx1zTUA8EE/s320/paul.jpg)
Ehrlich was born on March 14, 1854, in Strehlen, Silesia (then part of
Germany), to a prosperous Jewish family. He was the son of Ismar Ehrlich and
his wife, Rosa, the aunt of bacteriologist Karl Weigert. Ehrlich's interest in
biology and chemistry led him to study medicine. He attended universities in
Breslau, Strasbourg, Frieberg-im-Briesgau, and Leipzig, earning his medical
degree in 1878. Ehrlich was fascinated by the reactions of cells and tissues to
dyes. Using aniline dyes, for example, Ehrlich investigated white blood cells. In
the process, he developed new ways of staining cells for research, including
the methylene blue stain for bacteria. Heinrich Koch used this stain whenhe
discovered the bacillus that causes tuberculosis.
In 1890, Ehrlich became a professor at the University of Berlin, where he
worked with Emil von Behring and Shibasaburo Kitasato on the study of immunity or
the body's own defense against disease. The group searched for a substance that
would give immunity against diphtheria using antitoxins. Antitoxins are antibodies
produced by the body's immune system to fight poisons invading the body.
Ehrlich worked on the chemical aspects of the study and, in 1892, the group
announced the development of a diphtheria antitoxin for medical use. Ehrlich
also pioneered the production of large quantities of the antitoxin using
horses. He shared the 1908 Nobel Prize in Physiology or Medicine with Soviet
biologist Elie Metchnikoff (1845-1916) for his work on immunity and serum therapy.
In 1894, Ehrlich was made director of a new institute for serum research in
Frankfurt, where he studied the concepts of active and passive
immunity and developed his "side-chain" theory of immunity to explain
how antitoxins work at the cellular level in response to toxins. Ehrlich also
continued his study of blood using staining techniques. Realizing that stains
colored bacteria but not surrounding cells, he looked for a way to combine the
stain with a substance that could kill the bacteria. This, he reasoned, could
be a "magic bullet" in the fight against bacterial diseases. He also
identified dyes, such as trypan red that had the ability to destroy
microorganisms on their own.
Ehrlich began working with organic compounds containing arsenic because he
felt its properties were similar to those of the nitrogen atoms that gave
trypan red its effectiveness. He studied literally hundreds of arsenic
compounds and by 1907 he had reached number 606, which he put aside because it
was not effective against trypanosomes. However, two years later Ehrlich's
assistant, Sahachiro Hata (1872-1938), discovered that the compound number 606
was effective against the dread disease syphilis. Caused by a microorganism
called a spirochete, syphilis meant a slow and painful death for
thousands of people. In 1910, Ehrlich announced that chemical 606, which he
called Salvarsan, could cure syphilis.
For several years, Ehrlich suffered personal and professional attacks
because of his work with syphilis. Some felt the disease was a just punishment
for sinful sexual behavior and attacked Ehrlich for searching for a cure. The
administration of the drug was also complicated, even risky at first, and when
a few patients died because doctors administering the drug failed to follow
Ehrlich's instructions, Ehrlich was accused of fraud. The attacks finally
ceased in 1914, when the German parliament at last endorsed his cure as
authentic.
Ehrlich was married in 1883 to Hedwig Pinkus. The couple had two daughters.
Unfortunately, the strain surrounding Ehrlich's controversial efforts to cure syphilis
took its toll on his health and he suffered a series of strokes during his last
year, which led to his death in Bad Homburg, Germany, in 1915.
7. Alexander Fleming (1881 – 1955)
Alexander Fleming was born in Ayrshire on 6 August 1881, the son of a
farmer. He moved to London at the age of 13 and later trained as a doctor. He
qualified with distinction in 1906 and began research at St Mary's Hospital
Medical School at the University of London under Sir Almroth Wright, a pioneer
in vaccine therapy. In World War One Fleming served in the Army Medical Corps
and was mentioned in dispatches. After the war, he returned to St Mary's.
In 1928, while studying influenza, Fleming noticed that mould had
developed accidentally on a set of culture dishes being used to grow the
staphylococci germ. The mould had created a bacteria-free circle around itself.
Fleming experimented further and named the active substance penicillin. It was
two other scientists however, Australian Howard Florey and Ernst Chain, a
refugee from Nazi Germany, who developed penicillin further so that it could be
produced as a drug. At first supplies of penicillin were very limited but by
the 1940s it was being mass-produced by the American drugs industry.
Fleming
wrote numerous papers on bacteriology, immunology and chemotherapy. He was
elected professor of the medical school in 1928 and emeritus professor of
bacteriology at the University of London in 1948. He was elected fellow of the
Royal Society in 1943 and knighted in 1944. In 1945 Fleming, Florey and Chain
shared the Nobel Prize in Medicine. Fleming died on 11 March 1955.
No comments:
Post a Comment