Introduction & History of Microbiology


Feb 20, 2013 (4 years and 3 months ago)




Introduction & History of Microbiology

I. Introduction:



is the science that studies organisms which ordinarily are


small to be
seen without a microscope. These organisms are
referred to as
microbes. Among these microorganisms are bacteria,

protozoa, viruses, yeast, molds,
parasitic worms, arthropods, etc.

B. Significance:

Microbiology asks and answers questions such as what are the beneficial and harmf
roles of microorganisms on earth, how humans defend themselves from disease, how
microorganisms could be used to produce food and drugs for our benefit, etc. We come
in contact with thousands of microorganisms in our everyday life, some are beneficial
nd a few pathogenic or able to cause disease.

1. Medicine:

Infectious diseases are diseases cause by microorganisms. About 12 million people
around the world die each year due to Infectious diseases which could be prevented or
cured through the use of
vaccines or medication (World Health Organization).

Approximately half of all deaths caused by infectious diseases each year can be
attributed to just three diseases: tuberculosis, malaria, and AIDS. Together, these
diseases cause over 300 million illness
es and more than 5 million deaths each year.
Even though the numbers seems staggering, of all the millions of microorganisms on
earth only about 2,000 produce human disease. The vast majority are beneficial by
providing us with their by
products of metabol
ism such as antibiotics, etc


2. Research:

Microorganisms have been used to study and clarify:




Cell physiology


3. Ecology:

Recycle nutrients. Some bacteria are able of converting nitrogen into

its usable
compounds to be used by plants, etc.

4. Industrial applications:

• Production of beer, wine, bread

• Genetic recombination and Biotechnology.

• New species to produce all kinds of proteins (
: eat up


• Acetobacter


cellulose fibers (strong fabric)

II. History of Microbiology

Some ancient civilizations recogn
ized that certain diseases were
communicable (passed
along) and they would isolate their sick.

The study of microbes began with actual observation.

A. A
ntonie Van Leeuwenhoek:

A linen merchant, Holland

round the 1600’s

His hobby was grinding lenses to

in his simple microscopes. He attained magnifications of

about 300 X (times) and his
lenses were of amazingly good quality.

All microscopes were
simple (meaning one lens).In 1677. He sent a letter to Scientific
Society of London with the

First description
of microorganisms like protozoa, algae
and even

Simple bacteria.

Meanwhile compound microscopes were being made and refined.


A simple microsco

has one lens

A compound microscope
has at least 2 lenses (one ocular and one

objective lens).

By 1767 Only 6 species were

known, but by 1838, ab
out 600 species were discovere.

Medical Microbiology History

• Now seems simple and obvious that mic
roorganisms cause infectious diseases, but
people had no idea about this at that time in history.

• Religious beliefs were the explanation for

disease as punishment from God
leprosy, outcasts, buried alive). This idea is still present with venereal di
seases (sexually



• Experiments produced evidence for the Germ theory formulated by the French
Louis Pasteur.

Germ Theory of Disease: infectious diseases are caused by microorganisms.

A specific microorganism c
auses a specific infectious disease.

However, idea that diseases were caused by specific microbes was advanced mainly by
two men:

Louis Pasteur (1822

1895) in France and

Robert Koch (1843

1910) in Germany.


Louis Pasteur:

Germ Theory completed so
me of the first studies showing that diseases could arise from
infection. These studies (with the work of other scientists) became known as the “Germ
Theory of Disease”.


Robert Koch (1876)

Showed that sheep Anthrax was caused by a bacterium. A rod shape
d, large, and could
form spores.

Discovered this by developing a method for isolating pure cultures of one specific kind
of bacteria.
Solid media
(before always grown in broth

mixed culture).

On solid media each isolated bacterium grows and divides into g
iving rise to a pure

Koch could then demonstrate that a particular bacterial species was the cause of a
particular disease.


Koch’s postulates:

Koch’s postulates: a series of proofs that verified the Germ Theory. They are the
standard for identify
ing pathogens.

1. Observe
similar looking microorganisms in all patients with similar disease (e.g.
anthrax = rods in blood of all infected sheep).

2. Isolate
the suspected microorganism in artificial media in the laboratory.

3. Inoculate
a healthy experim
ental animal and observe the experimental animal come
down or show signs and symptoms of disease.

4. Re
the organism from the experimental animal.
If all these steps are followed
and it confirms, it has been proven that this microorganism is the ca
use of the disease.

From 1879

1889, Koch


his students isolated the bacteria causing:

• Tuberculosis

• Cholera

• Typhoid

• Diphtheria

• Pneumonia

• Meningitis

• Gonorrhea

• Tetanus.