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<p>Louis Pasteur (1822-1895) and Robert Koch (1843-1910) were contemporaries of Cohn&rsquo;s and are often considered to be the founders of <strong>medical microbiology</strong>. Pasteur is most famous for his <a href="http://www.realtorrentz.com/cat.php?id=2">series</a> of experiments designed to disprove the then widely held theory of spontaneous generation, thereby solidifying microbiology&rsquo;s identity as a biological science. Pasteur also designed methods for food preservation (pasteurization) and vaccines against several diseases such as anthrax, fowl cholera and rabies. Robert Koch is best known for his contributions to the germ theory of disease, proving that specific diseases were caused by specific pathogenic microorganisms. He developed a series of criteria that have become known as the Koch's postulates. Koch was one of the first scientists to focus on the isolation of bacteria in pure culture resulting in his description of several novel bacteria including <em>Mycobacterium tuberculosis</em>, the causative agent of tuberculosis. </p>

<p>While Louis Pasteur and Robert Koch are often considered the founders of microbiology, their work did not accurately reflect the true diversity of the microbial world because of their exclusive focus on microorganisms having medical relevance. It was not until the work of Martinus Beijerinck (1851-1931) and Sergei Winogradsky (1856-1953), the founders of <strong>general microbiology</strong> (an older term encompassing aspects of microbial physiology, diversity and ecology), that the true breadth of microbiology was revealed. Martinus Beijerinck made two major contributions to microbiology: the discovery of viruses and the development of enrichment culture techniques. While his work on the Tobacco Mosaic Virus established the basic principles of virology, it was his development of enrichment culturing that had the most immediate impact on microbiology by allowing for the cultivation of a wide range of microbes with wildly different physiologies. Sergei Winogradsky was the first to develop the concept of chemolithotrophy and to thereby reveal the essential role played by microorganisms in geochemical processes. He was responsible for the first isolation and description of both nitrifying and nitrogen-fixing bacteria.</p>

<h2><span class="mw-headline">Types of microbiology</span></h2>