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micro_outline - 1 Microbiology An Introduction 1...

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1. Microbiology - An Introduction 1. Microbiology is the study of organisms too small to be clearly seen by the unaided eye (i.e., microorganisms); these include viruses, bacteria, archaea, protozoa, algae, and fungi 2. Some microbes (e.g., algae and fungi) are large enough to be visible, but are still included in the field of microbiology; it has been suggested that microbiology be defined not only by the size of the organisms studied but by techniques employed to study them (isolation, sterilization, culture in artificial media) 2. The Discovery of Microorganisms 1. Invisible living creatures were thought to exist and were thought to be responsible for disease long before they were observed 2. Antony van Leeuwenhoek (1632-1723) constructed microscopes and was the first person to observe and describe microorganisms accurately 3. The Conflict over Spontaneous Generation 1. The proponents of the concept of spontaneous generation claimed that living organisms could develop from nonliving or decomposing matter 2. 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 3. 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 4. 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 5. Louis Pasteur (1822-1895) trapped airborne organisms in cotton; he also heated the necks of flasks, drawing them out into long curves, sterilized the media, and left the flasks open to the air; no growth was observed because dust particles carrying organisms did not reach the medium, instead they were trapped in the neck of the flask; if the necks were broken, dust would
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