Contribution of Louis Pasteur in Microbiology

Prepared By: Purvi SoniClass: B.Pharm/Sem-V

A.R.College of Pharmacy, V.V.Nagar

December 27, 1822 – September 28, 1895)

"Imagination should give wings to our thoughts, but we always need decisive

experimental proof.”

These are the famous words of Louis Pasteur who was one of the greatest scientists of the

nineteenth century.

Louis Pasteur• 1847 to 1862 (Pasteur As a Physicist and a Chemist)• Crystallography• Alcoholic Fermentation• 1862 to 1877 (Pasteur As a Biologist)• Spontaneous Generation• Pasteurization: (Wine & Beer Diseases)• Silk Worm Diseases• 1877 to 1887 (Pasteur As a Microbiologist)• Germ Theory of Disease• Rabies

Contribution in Microbiology

Disproved Spontaneous Theory Fermentation & Pasteurization Germ theory of DiseaseI. AnthranxII. Silkworm Disease VaccinationI. RabiesII. Chicken Cholera

Spontaneous Generation

• Until the second half of the nineteenth century, Many scientists and philosophers believed that some form of life could arise spontaneously from nonliving matter; they called this hypothetical process Spontaneous Generation

• With a series of ingenious experiment persuasive experiments;

• Pasteur demonstrated that microorganism are present in the air and can contaminate sterile solutions, but air itself does not create microbes.

Experiment Procedure

1. Pasteur first poured beef broth into a long necked flask.

2. Next he heated the neck of the flask and bent it into an S-shaped curve; then he boiled the broth for several minutes.

3. Microorganism did not appear in the cooles solution, even after long periods.

Pasteur’s experiments with “swan-necked” flasks

Steam escapesfrom open endof flask.

Infusionis heated.

Infusion sits;no microbes appear.

Months

Air moves inand out of flask.

Infusion remainssterile indefinitely.

Dust fromair settlesin bend.

Fermentation and Pasteurization

• Pasteur demonstrated that fermentation is caused by the growth of micro-organisms, and the emergent growth of bacteria in nutrient broths is due not to spontaneous generation, but rather to biogenesis

• (Omne vivum ex vivo "all life from life").

Pasteur's application of the scientific method

Observation:

Hypothesis Experiment Observation Conclusion

Fermentinggrape juice

Microscopic analysisshows juice containsyeasts and bacteria.

Day 1: Flasks of grapejuice are heated sufficientlyto kill all microbes.

Day 2

I. Spontaneousfermentationoccurs.

II. Air fermentsgrape juice.

III. Bacteria fermentgrape juiceinto alcohol.

IV. Yeasts fermentgrape juiceinto alcohol. Juice in flask is

inoculated withyeast and sealed.

Juice in flask is inoculated withbacteria and sealed.

Flask remainsopen to airvia curved neck.

Flask is sealed.

No fermentation;juice remainsfree of microbes

No fermentation;juice remainsfree of microbes

Bacteria reproduce;acids are produced.

Yeasts reproduce;alcohol is produced.

Reject hypothesis I.

Reject hypothesis II.

Modify hypothesis III; bacteria fermentgrape juice intoacids.

Accept hypothesis IV; yeasts fermentgrape juice intoalcohol.

Pasteur effect• The realization that specific organisms were involved in fermentation was

further supported by Pasteur’s studies of butyric acid fermentation.

• These studies led Pasteur to the unexpected discovery that the fermentation process could be arrested by passing air (that is, oxygen) through the fermenting fluid, a process known today as the Pasteur effect.

• He concluded that this was due to the presence of a life-form that could function only in the absence of oxygen.

• This led to his introduction of the terms aerobic and anaerobic to designate organisms that live in the presence or absence of oxygen, respectively.

• He further proposed that the phenomena occurring during putrefaction were due to specific germs that function under anaerobic conditions.

Pasteurization• Pasteur readily applied his knowledge of microbes and

fermentation to the wine and beer.• In 1863, at the request of the emperor of France, Napoleon

III, Pasteur studied wine contamination and showed it to be caused by microbes.

• To prevent contamination, Pasteur used a simple procedure: he heated the wine to 50–60 °C (120–140 °F), a process now known universally as pasteurization.

• It is applied to many foods and beverages, particularly milk.

The Germ Theory of Disease

• Before the time of Pasture , effective treatments for many disease were discovered by trial and error, but the causes of disease were unknown.

• The realization that Yeast plays a crucial role in fermentation was the first link between the activity of a microorganism and physical-chemical changes in organic materials.

• The discovery alerted scientists to the possibility that microorganisms might have similar relationships with plants and animals- specifically that microorganisms might cause disease.

• This idea was known as the Germ theory of Disease.• In that connection, he carefully studied and discovered

various infectious diseases such as staphylococcus, streptococcus and pneumococcus.

• He prescribed methods of attenuating microbe virulence (chicken cholera and sheep anthrax).

• He followed his discovery of germ theory with the utilization of vaccines to prevent diseased like cholera, anthrax and swine erysipelas.

Work with silkworms• In the middle of the 19th century, a mysterious disease had attacked

French silkworm nurseries. • Silkworm eggs could no longer be produced in France. • Pasteur knew virtually nothing about silkworms, but upon the

request Pasteur took charge of the problem, accepting the challenge and seizing the opportunity to learn more about infectious diseases.

• He soon became an expert silkworm breeder and identified the organisms that caused the silkworm disease.

• After five years of research, he succeeded in saving the silk industry through a method that enabled the preservation of healthy silkworm eggs and prevented their contamination by the disease-causing organisms.

ANTHRAX

• In 1879• Pasteur had a particular

interest in the disease anthrax.

• Anthrax is an infectious disease that affects cattle, sheep, and other livestock that can be transmitted to man.

During this time, anthrax was

responsible for killing large

populations of sheep in France, and this was detrimental to

the economy.

• Pasteur carefully studied anthrax and noticed that some cattle developed the disease more severely than others. So he decided to inject two cattles with a strong dose of the anthrax bacteria, fully expecting them to die.

• Did they die?

• To Pasteur's amazement neither of the cows developed the disease. Later, he found that both animals had already suffered from anthrax.

• Pasteur supposed that if it were possible to give an animal a mild attack, this might be sufficient to prevent the animal from getting the disease later on.

• Pasteur’s hypothesis was correct. He eventually succeeded in producing a mild, weakened, harmless culture of anthrax bacteria. He then took this culture and vaccinated hundreds of livestock, and they were then immune to the disease.

Rabies

• Pasteur is predominantly well-known for his work with rabies also known as hydrophobia. Rabies is a highly contagious, infectious disease that attacks the central nervous system.

RABIES VACCINE• Louis first studied the saliva of animals and humans who had died of rabies and

confirmed the presence of a specific microbe, too small to be seen through a microscope, which we call a virus now.

• He then examined tissue from the brain and spinal cords of some of the victims and found the virus there too. Louis became certain it would be possible to make a vaccine using weakened strains of the disease-causing organism (attenuated vaccine) from a weakened strain of the virus.

• At last, Louis was satisfied that he could prevent the dreaded disease in dogs, but he did not dare test the drug on a human volunteer. If Louis's rabies vaccine was found to be too strong for use in humans, trials using healthy people could result in their catching the dreaded disease.

• On 6 July, 1885• A nine-year-old boy, Joseph Meister, was brought to him by his distraught

mother. • Joseph had been bitten many times by a rabid dog in his village, alsace

two days before, and she begged Louis to try to save her son. • If the vaccine failed, Louis knew he would not be blamed for Joseph's

death, but if Louis did nothing, Joseph was likely to die anyway. • Louis injected the vaccine into Joseph twelve times over the course of ten

days. • Joseph's bites healed, and he went home several days after the treatment

without having contracted rabies.

This milestone transformed Pasteur into a legend.

Bibliography• Textbook : An Introduction to Microbiology; Tortora; Eighth

Edition.• http://www.britannica.com/EBchecked/topic/445964/Louis-

Pasteur/281418/Implications-of-Pasteurs-work• https://explorable.com/discovery-of-pasteurization• http://www.britannica.com/EBchecked/topic/445964/Louis-

Pasteur/281418/Implications-of-Pasteurs-work• http://www.angelfire.com/al/aloysius/rabies.html• http://en.wikipedia.org/wiki/Loiuspasteur