irrors known as the Abbe condenser. In 1883, Koch interrupted his studies on tuberculosis to study cholera in Egypt and India, and isolated a comma shaped bacillus, confirming John SnowÆs contention made 30 years earlier that diseases could be waterborne. He also studied malaria, the plague, and sleeping sickness.
More recently, in the 1900s, Ronald Ross of England showed that mosquitos transmitted malaria; David Bruse showed that the tsetse fly causes sleeping sickness; Daniel E. Salmon gave his name to Salmonella, the cause of typhoid fever; Howard Taylor Ricketts showed the microorganism responsible for Rocky Mountain Spotted fever in the bloodstream, and that it is carried by ticks; and Walter Reed discovered in Cuba that mosquitos transmit yellow fever. As for beneficial bacteria, Sergius Winogradsky showed some bacteria use carbon dioxide to synthesize carbohydrates; and Martinus Beijerinck showed that some bacteria trap nitrogen in the soil for plants to use. These early studies were known as the Golden Age of microbiology.
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