Chapter 5 : Where Do Microbes Come From?

Abstract:

Animals that were not seen firsthand to be born by natural reproduction were considered by the ancients to come into the world through spontaneous generation, as the result of the combined action of heat, water, air, and putrefaction. Numerous natural philosophers and scientists occupied themselves for centuries with the question of spontaneous generation, and it was still a hot topic when Louis Pasteur came onto the scene in the 1870s. By that time, it was clear that spontaneous generation of mice, maggots, etc., was unprovable and extremely dubious, and the argument then shifted to microbes. Pasteur devised ingenious ways of proving that microbes also do not arise by spontaneous generation, but that they are produced instead from other microbial cells. One of the important procedures used in Pasteur’s studies was preliminary destruction of all living microbes in nutrient fluids by heating, typically by boiling solutions for 15 to 20 minutes. More recent studies conducted by scientists at the United States Geological Survey have demonstrated that large numbers of living microbes are carried over long distances in clouds of dust, for example, across the Atlantic Ocean from African deserts.