#Infodump2

The First Observations:

Robert Hooke (1665) – Using a crude microscope observed a thin slice of cork reporting the smallest structural unit ‘cells’ derived from the Latin word ‘cellula’ which means small compartment. His most significant publication was Micrographia, a 1665 volume detailing experiments he had made. Hooke’s microscope’s poor resolution despite being capable of viewing large cells lacked the ability to clearly see microbes. His discovery marked the beginning of cell theory.

Antonie van Leeuwenhoek (Dutch merchant and amateur scientist)– First to actually observe live microorganisms through his simple single-lens microscope. During his lifetime by pursuing his hobby of lens grinding and microscope building he had made nearly 250 microscopes consisting of home-ground lenses mounted in brass and silver, of which the most powerful one could magnify about 200-300 times.

He made detailed diagrams of ‘animalcules’ he found in rainwater, his own faeces and in material scraped from his teeth, producing precise and appropriate descriptions of bacteria, fungi and protozoa. A series of over 200 letters were written by him to the Royal Society of London between 1673 and 1723 describing his ‘animalcules’. He is considered the ‘Father of Microbiology’ because of his remarkable contribution in the field.

The confirmation of microorganisms’ existence spurred interest among the scientist to unearth the mystery behind the origin of living organisms. Many scientists, until the second half of the nineteenth century, believed that such life forms could arise through spontaneous generation.

Many experiments were centred around resolving the controversy of spontaneous generation. The notable ones are listed as follows:

Francesco Redi (1688): Strongly opposed to the theory of spontaneous generation he carried out an experiment to demonstrate that decaying meat cannot spontaneously produce maggots.

• Experiment 1: Two jars filled with decaying meat. First jar: left unsealed; Second jar: sealed

• Observation: In first jar: flies laid eggs on the meat which developed into larvae

• In second jar: No flies could enter hence eggs were laid on the meat therefore no maggots appeared.

• Disapproval: Antagonist of Redi’s experiments opposed by claiming that spontaneous generation required the presence of fresh air.

• Second experiment setup by Redi: The same setup as the first experiment was followed with the exception of the second jar being covered with a fine net instead of being sealed allowing the passage of fresh air.

• Observation: larvae failed to appear in the gauze-covered jar despite the presence of fresh air.

• Conclusion: Maggots appeared only when flies were allowed to leave their eggs on the meat.

However, small organisms such as van Leeuwenhoek’s “animalcules” were still believed by many scientists to be simple enough to be generated from non-living material.

John Needham (1745): Strengthened the case of spontaneous generation (strongest supporter of spontaneous generation)

• Experiment: Poured heated nutrient broths (corn broth and chicken broth) in covered flask.

• Observation: Microorganisms teeming in the cooled broth present in the covered flasks.

• Conclusion: Claimed spontaneous generation of microbes from fluids.

Lazzaro Spallanzani (1729–1799): Italian scientist who tried to refute John Needham’s experiment by suggesting that air containing microorganisms had probably entered Needham’s solution after they were boiled. He performed hundreds of carefully executed experiments using heated broth.

• Experiment: Heated nutrient fluid after the flask was sealed.

• Observation: No microbial growth had developed in the flask allowing his flasks to remain clear unless the flasks were subsequently opened to air.

• Opposing statement by Needham: He responded by claiming that ‘vital force’ was essential for spontaneous generation of microscopic beings which had been destroyed by the heat and excluded by sealing the flasks. Thus, not preventing new life force from entering and allowing spontaneous generation to occur.

Next argument against spontaneous generation was independently delivered by two other investigators:

Franz Schluze (1815-1873) – performed Needham’s experiment except he passed air via strong acid solutions into his boiled broth.

Theodor Schwann (1810-1882) – he passed his air in to the flasks through red hot tubes.

Observation: Microbes did not appear in either case.

Disagreement: Growth cannot be supported by acid and heat altered air, was the argument delivered by the die-hard advocates of spontaneous generation.

H. Schröder and T. von Dusch (1850): Carried out a more convincing experiment by passing air through cotton into the flasks, subsequently filtering the microbes out by the cotton fibres, thus preventing microbial growth. This developed the basic technique of using cotton stoppers for plugging bacterial culture tubes.

The concept of spontaneous generation was revived and strongly supported a last time by Felix Archimede Pouchet (1800-1872) who published an extensive report “proving” the theory in 1859.

Finally exasperated with all the debates and speculations, Louis Pasteur performed a series of experiments bringing an end to this argument for once and for all.