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Van Leeuwenhoek's engravings (1.5x), 1695

Microbiology as a science was born in 1674 when Antony van Leeuwenhoek (1632-1723), an inquisitive Dutch drapery merchant, peered at a drop of lake water through a glass lens that he had carefully ground. It was known for several centuries previous that curved glass would magnify objects, but it took the skillful hands of a craftsman coupled with the questioning mind of an amateur scientist to revolutionize the understanding of the world in which we live. What he observed through this simple magnifying glass was undoubtedly one of the most startling and amazing sights that humans have ever beheld—the first glimpse of the world of microbes. As van Leeuwenhoek wrote in a letter to the Royal Society of London, he saw

"Very many little animalcules, whereof some were roundish, while others a bit bigger consisted of an oval. On these last, I saw two little legs near the head, and two little fins at the hind most end of the body. Others were somewhat longer than an oval, and these were very slow a-moving, and few in number. These animalcules had diverse colours, some being whitish and transparent; others with green and very glittering little scales, others again were green in the middle, and before and behind white; others yet were ashed grey. And the motion of most of these animalcules in the water was so swift, and so various, upwards, downwards, and round about, that 'twas wonderful to see."

It is quite surprising that not only was van Leeuwenhoek able to see bacteria, but he even described their numerous shapes (chapter opening figure). His simple microscope increased the size of the object he was viewing only about 300 times. Microscopes commonly used in the laboratory today magnify objects over 1,000 times. Seeing small objects through the lens of a microscope depends not only on magnifying the size of the specimen being viewed, but also on illuminating it. Van Leeuwenhoek must have developed an unusually good method for lighting the specimens to see what he reported.

—A Glimpse of History

MICROORGANISMS ARE THE FOUNDATION FOR ALL life on earth. It has been said that the twentieth century was the age of physics. Now we can say that the twenty-first century will be the age of biology and biotechnology, with microbiology as the most important branch. It is generally believed that microorganisms have existed on earth for several billion years, and over this time, plants and animals have evolved from these microscopic forms (figure 1.1). Microorganisms themselves have also evolved into a very diverse group. They vary in their appearance, in their ability to carry out different biochemical transformations, in their remarkable ability to grow in a wide variety of different environments, and in their interactions with other microorganisms and all other forms of life, in particular humans. One of their most important characteristics is their ability to quickly change their properties and adapt to a changing environment. And yet, for all of these amazing abilities, we cannot really assess their true importance and capabilities because less than one in a hundred species can be grown in the laboratory! As the exploration of the microbial world continues there are certain to be many new surprises.

Chapter 1 Humans and the Microbial World

Chapter 1 Humans and the Microbial World

Figure 1.1 Microfossil Resembling Cyanobacteria The microfossil Palaeolyngbya isolated from shale in eastern Siberia is 950 million years old.

designed to determine whether microbes could arise from nonliving material consisted of boiling organic material in a vessel to kill all forms of life (sterilize) and then sealing the vessel to prevent any air from entering. If the solution became cloudy after standing, then one could conclude that microorganisms must have arisen from the organic material in the vessel, thus supporting the theory of spontaneous generation. Unfortunately, this experiment did not consider several alternative possibilities: that the flask might be improperly sealed, that microorganisms might be present in the air, or that boiling might not kill all forms of life. Therefore, it was not surprising that different investigators obtained different results when they performed this experiment.

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