#Infodump3

The theory of spontaneous generation remained unresolved until 1858, when it was contested by the German scientist Rudolf Virchow with his theory of Biogenesis. Unable to furnish a scientific proof the debate about spontaneous generation continued till 1861, when the French scientist Louis Pasteur stepped up to resolve the issue.

Louis Pasteur (1861): He demonstrated that sterile solutions can be contaminated by the microorganisms present in the air but the air itself is does not create microbes.

Experiment 1: Boiled beef broth in several short-neck flasks, left some open and allowed them to cool and the other flasks were sealed after boiling.

Observation: The open flasks were contaminated after a few days while the sealed flasks remained free of microorganism.

Conclusion: He reasoned that non-living matter were contaminated due to the presence of microbes in the air.

Experiment 2: He prepared open-ended, long-necked flasks with their necks shaped in the form of the letter S. Broth was placed in these flasks, boiled and cooled. The air entering through the neck was untreated and unfiltered.

Observation: Broth in the flasks didn’t decay not did they harbour any microbes, even after months. The curved neck of the flasks allowed the passage of air but trapped any air-borne microorganisms which could contaminate the broth.

Conclusion: Discredited the claim of spontaneous generation. Demonstrated that microbes can be destroyed by heat and revealed that methods can be devised to bar the entry of airborne microbes to nutrient environments.

The basis of aseptic techniques was borne out these discoveries making them a fundamental practice in laboratory and numerous medical procedures.

Louis Pasteur is known as the “Father of Modern Microbiology/ Father of Bacteriology”.

John Tyndall (1877) (English physicist): He dealt the final blow to spontaneous generation in the year 1877. He performed experiments in an aseptically designed box to prove that dust carried germs, demonstrating that in the absence of dust sterile broth remained free of microbial growth for an indefinite period of time.

Pasteur’s work opened a new door to the world of microbiology which was followed by an explosion of new discoveries. The period between 1857 and 1914 has been aptly titled as the “Golden Age of Microbiology” due to the rapid advancements made, with Pasteur and Robert Koch’s contribution at the forefront in establishing Microbiology as a significant part of bioscience. These years include discoveries about the relationship between microbes and disease, the role of immunity in preventing and curing diseases, chemical activities of microorganisms, evolution of microscopy, and the development of vaccines and surgical techniques.

Some of the major events in this era are recounted bellow.

The involvement of microbes in causing diseases is a relatively new discovery.

Girolamo Fracastoro of Verona (1478–1553) (physician) had proposed that disease was caused by invisible organisms transmitted from one person to another going as far as suggesting these invisible living creatures to be self-replicating which act on the humors of the body to cause diseases. His ideas were way ahead of his time as these propositions were made nearly 200 years before the invention of microscope.

Von Plenciz (1762) stated that diseases were caused by living agents and different germs were responsible for different diseases.

Oliver Wendell Holmes (1809-1894), physician claimed that puerperal fever, a disease associated with childbirth was contagious caused by germs passed on from one mother to other by midwives and physicians and had written about his views in ‘The Contagiousness of Puerperal Fever’ in the year 1842.

It was later in 1865, after Pasteur’s work on fermentation and pasteurisation, he was called upon to investigate pebrine, a silkworm disease which was ruining the silk industry throughout Europe. Agostino Bassi an amateur microscopist, in the year 1835, had proven another silkworm disease which was caused by fungus. Based on this data, Pasteur had found the recent silkworm disease to be due to protozoan infection and had helped in developing a method for identifying afflicted silkworm moths.

In 1860s, Joseph Lister, an English surgeon, inspired by Ignaz Semmelweis (1840s), a Hungarian physician’s demonstration that infections were routinely transmitted from one patient to another when physicians did not disinfect their hands before treatment as well as Pasteur’s work connecting animal disease to microbes, applied germ theory to medical procedures.

Disinfectant were not in use at that time though Lister was aware property of phenol (carbolic acid) to kill bacteria and hence began treating surgical wounds with a phenolic solution. This practise was quickly adopted by other surgeons as it proved highly effective in reducing the incidence of infections and deaths. Lister findings verified that surgical wound infections were caused by microorganisms and his technique was one of the earliest medical attempts to combat such situations.

Robert Koch (1876): a German physician, was Pasteur’s young rival in the race to discover the cause of anthrax, a disease that was destroying cattle and sheep in Europe.

Experiment: He discovered rod-shaped bacteria now known as Bacillus anthracis in the blood of cattle that had died of anthrax. He cultured the bacteria on nutrients and then injected samples of the culture into healthy animals. When these animals became sick and died, Koch isolated the bacteria in their blood and compared them with the originally isolated bacteria.

Observation: He found that the two sets of blood cultures contained the same bacteria.

This lead him to establish a set of 4 postulates as listed below:

Koch's postulates:

1. The microorganism or other pathogen must be present in all cases of the disease.

2. The pathogen can be isolated from the diseased host and grown in pure culture.

3. The pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal.

4. The pathogen must be reisolated from the new host and shown to be the same as the originally inoculated pathogen.