#5 Theory of Spontaneous Generation | The BioChemistry Guide | 2014

Theories of Spontaneous Generation

Early Investigations into Microorganisms

• Before microorganisms were observed, there were suspicions about their existence and role in diseases. Various scientists believed in the theory of spontaneous generation.

Anthony van Leeuwenhoek's Discoveries

• The first accurate observation of microorganisms was made by Anthony van Leeuwenhoek, who constructed simple microscopes that could magnify objects 50 to 300 times.

• Van Leeuwenhoek sent detailed letters to the Royal Society of London describing his discoveries, which included bacteria and protozoa.

The Challenge to Spontaneous Generation

• The theory of spontaneous generation posited that living organisms could arise from non-living matter; even Aristotle supported this idea for simpler invertebrates.

• Italian physician Francesco Redi challenged this theory through experiments with decaying meat, demonstrating that maggots did not spontaneously generate but came from fly eggs.

Further Experiments on Spontaneous Generation

• Despite Redi's findings, some argued that microorganisms might still arise spontaneously. John Needham conducted experiments with mutton broth and concluded organic matter contained a "vital force."

• Lazaro Spallanzani improved upon Needham’s work by sealing flasks containing broth and boiling them; he found no growth unless air was introduced.

Louis Pasteur's Definitive Experiment

• Louis Pasteur further investigated the role of air in microbial growth. He filtered air through cotton and discovered trapped particles resembling plant spores.

• Pasteur designed an experiment using swan-necked flasks to test if nutrient broth could spontaneously generate life. His results showed that dust particles caused contamination when exposed to air.