Microbiology

Microbiology Study Guide

Chapter 1: Introduction to Microbiology Objectives 1. Know the history and evolution of microorganisms. 2. Understand germ theory of disease and ways to combat infectious diseases. 3. Identify different categories of microorganisms. 4. Explain microbial laboratory techniques. 1.1 Early History of Microbiology

Discovery of Microorganisms A long time ago, invisible living creatures were thought to exist. They were held responsible for disease long before they were observed. In the mid-1600s, Robert Hooke was the first person to observe strands of fungi. After a few decades, Antony van Leeuwenhoek observed microscopic organisms and named them animalcules. He was the first one who discovered and provided accurate descriptions of protozoa, bacteria, and fungi. He constructed over 400 microscopes as well. After he died in 1723, the theory of spontaneous generation was debated by many scientists. Spontaneous Generation Many scientists prior to the second half of the 1800s believed in spontaneous generation, claiming that living organisms could develop from nonliving or decomposing matter. Many people believed that animals were born of the dirt in the ground, and flies were created by the manure from which they fed. There were some scientists that disagreed with this theory for centuries before it was rejected, and in contrast, many scientists who believed in it and attempted to prove the theory. Some prominent scientists include: • Francesco Redi (1626-1697) challenged this concept by showing that maggots on decaying meat came from fly eggs deposited on the meat, and not from the meat itself. • John Needham (1713-1781) showed that mutton broth boiled in flasks and then sealed could still develop microorganisms, which supported the theory of spontaneous generation. • Lazzaro Spallanzani (1729-1799) showed that flasks sealed and then boiled had no growth of microorganisms, and he proposed that air carried germs to the culture medium. He also commented that external air might be needed to support the growth of animals already in the medium; the latter concept was appealing to supporters of spontaneous generation. Germ Theory of Disease Several events led to the development and proof that microbes cause disease, otherwise known as germ theory. Some of the theories propounded by early scientists include: • Hieronymus Fracastorius (Girolamo Fracastoro) wrote "On Contagion" in 1546, which is the first known discussion of the phenomenon of contagious infection.

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