neck flasks, Fig. 2.2a) and unheated so as “not to disturb the
air,” he brought to a boil organic fluids where he could show,
through microscopic observations and methods of bacterial
cultures, that sterilized liquids were not recontaminated.
These sealed and still sterile vials can still be seen in the
Pasteur Museum at the Pasteur Institute in Paris. In parallel,
the British physicist John Tyndall showed that air free of
“particles” and optically clear did not cause degradation of
organic substances, and resolved the problem of heat resistance of bacterial endospores by discontinuous heat
treatments (Tyndall 1877). He was able to eliminate
endospores that are resistant to boiling by successive heating
cycles. The time between two heating cycles (24 h) allowed
the germination of spores that had resisted the first heat
treatment; such germinated bacteria were then killed by a
second heating to a boil. This sterilization technique has
been called tyndallization*. His works were complementary to those of the German botanist Ferdinand Julius Cohn
(1876) who described the endospores of Bacillus subtilis and
their heat resistance properties. The studies of Pasteur,
Tyndall, and Cohn have shown among other things that
bacteria could survive in hostile environments by producing
endospores and that these spores were airborne and carried
by currents and could be scattered from one ecosystem to
another.
A pioneer of the theory of microbial diseases was Ignaz
Philipp Semmelweis (1818–1865) of Hungarian origin, a
doctor at the obstetrics ward of the Vienna hospital. He
had noticed that the death rate from puerperal fever in
recently delivered women varied in different wards, ranging
from 1 to 2 % in a service run by midwives to 30 % in
another service staffed by physicians practicing dissections
that were then not followed by hand washings. In 1847, he
proposed to make hand washing mandatory when moving
between services, which permitted to reduce quickly the
death rate (Semmelweis 1861) but also caused deep resentment from upset department heads who greatly doubted the
existence of germs as shown from the following quotation
from the department head involved: “Herr Semmelweis
claims that we carry on our hands little things that would
be the cause of puerperal fever. What are these little things,
those particles that no eye can see? This is ridiculous! The
little things exist only in the imagination of Herr
Semmelweis!”
2.3
The Beginnings of Microbiology
The major developments of microbiology from 1860 until
the mid-twentieth century were largely influenced by the
work of Louis Pasteur (Fig. 2.2b) and Robert Koch
(Fig. 2.3).
Louis Pasteur was born in Dole (France) in 1822, made
parts of his studies at the “Ecole Normale Supe ´rieure” (ENS)
in Paris. He was appointed professor of physics and chemistry, successively in Dijon, at the Faculty of Sciences of
Strasbourg, at the Faculty of Sciences of Lille, and finally
to the ENS in Paris. Strongly interested in the socioeconomic
problems of his time, Pasteur, who had been trained as an
organic chemist, has very quickly begun work on fermentation because of the problems encountered by producers of
wine and beer and distillers and manufacturers of vinegar.
His studies on fermentation between 1857 and 1876 have
Fig. 2.1 (a) Antoni van Leeuwenhoek (1632–1723) (Copyright: courtesy of the Archives of the School of Microbiology of Delft, Technological
University of Delft). (b) Microscope of A. van Leeuwenhoek (magnification  200) (Modified from Wikipedia)
2 Some Historical Elements of Microbial Ecology
11
air,” he brought to a boil organic fluids where he could show,
through microscopic observations and methods of bacterial
cultures, that sterilized liquids were not recontaminated.
These sealed and still sterile vials can still be seen in the
Pasteur Museum at the Pasteur Institute in Paris. In parallel,
the British physicist John Tyndall showed that air free of
“particles” and optically clear did not cause degradation of
organic substances, and resolved the problem of heat resistance of bacterial endospores by discontinuous heat
treatments (Tyndall 1877). He was able to eliminate
endospores that are resistant to boiling by successive heating
cycles. The time between two heating cycles (24 h) allowed
the germination of spores that had resisted the first heat
treatment; such germinated bacteria were then killed by a
second heating to a boil. This sterilization technique has
been called tyndallization*. His works were complementary to those of the German botanist Ferdinand Julius Cohn
(1876) who described the endospores of Bacillus subtilis and
their heat resistance properties. The studies of Pasteur,
Tyndall, and Cohn have shown among other things that
bacteria could survive in hostile environments by producing
endospores and that these spores were airborne and carried
by currents and could be scattered from one ecosystem to
another.
A pioneer of the theory of microbial diseases was Ignaz
Philipp Semmelweis (1818–1865) of Hungarian origin, a
doctor at the obstetrics ward of the Vienna hospital. He
had noticed that the death rate from puerperal fever in
recently delivered women varied in different wards, ranging
from 1 to 2 % in a service run by midwives to 30 % in
another service staffed by physicians practicing dissections
that were then not followed by hand washings. In 1847, he
proposed to make hand washing mandatory when moving
between services, which permitted to reduce quickly the
death rate (Semmelweis 1861) but also caused deep resentment from upset department heads who greatly doubted the
existence of germs as shown from the following quotation
from the department head involved: “Herr Semmelweis
claims that we carry on our hands little things that would
be the cause of puerperal fever. What are these little things,
those particles that no eye can see? This is ridiculous! The
little things exist only in the imagination of Herr
Semmelweis!”
2.3
The Beginnings of Microbiology
The major developments of microbiology from 1860 until
the mid-twentieth century were largely influenced by the
work of Louis Pasteur (Fig. 2.2b) and Robert Koch
(Fig. 2.3).
Louis Pasteur was born in Dole (France) in 1822, made
parts of his studies at the “Ecole Normale Supe ´rieure” (ENS)
in Paris. He was appointed professor of physics and chemistry, successively in Dijon, at the Faculty of Sciences of
Strasbourg, at the Faculty of Sciences of Lille, and finally
to the ENS in Paris. Strongly interested in the socioeconomic
problems of his time, Pasteur, who had been trained as an
organic chemist, has very quickly begun work on fermentation because of the problems encountered by producers of
wine and beer and distillers and manufacturers of vinegar.
His studies on fermentation between 1857 and 1876 have
Fig. 2.1 (a) Antoni van Leeuwenhoek (1632–1723) (Copyright: courtesy of the Archives of the School of Microbiology of Delft, Technological
University of Delft). (b) Microscope of A. van Leeuwenhoek (magnification  200) (Modified from Wikipedia)
2 Some Historical Elements of Microbial Ecology
11