How did John Tyndall's experiments support Louis Pasteur's findings about microbes in air?

In 1876, the physicist John Tyndall provided critical experimental support for Louis Pasteur’s germ theory by demonstrating that air carries particulate matter capable of supporting microbial growth.1

While Pasteur had previously used "swan-neck" flasks to show that sterile broth remained uncontaminated unless exposed to airborne particles, Tyndall developed an apparatus to verify the purity of air. By illuminating air under specific conditions, he utilized the Tyndall effect to detect the presence of dust and particles. Tyndall’s experiments proved that when air was confirmed to be free of these particles, it could not induce the growth of microorganisms in nutrient media.213

These findings reinforced Pasteur’s conclusion that microbes do not arise through spontaneous generation but are instead introduced by preexisting forms present in the atmosphere. Together, their work effectively dismantled the doctrine of spontaneous generation and established the foundation for modern microbiology.1