Chapter 1: Evolution of Microorganisms & Microbiology

Evolution of Microorganisms & Microbiology life forms, which are generally defined as being 1 millimeter or less in diameter and too small to be seen clearly by the unaided eye, perform ecological functions critical for planetary survival. Key evolutionary concepts include the historical role of cyanobacteria in initiating the great oxidation event approximately 2.4 billion years ago, fundamentally changing Earth’s atmosphere and setting the stage for oxygen-consuming organisms to evolve. Furthermore, only bacteria possess the unique metabolic capability for nitrogen fixation, making essential organic nitrogen available to plants, animals, and other microbes. Microorganisms are also responsible for the necessary degradation of dead organic material and the production of diverse common foods like wine and yogurt. Although only a fraction—less than one percent—of all microbial species cause infectious disease, resulting in millions of preventable deaths annually, most vaccines and antibiotics used to combat these pathogens are ironically derived from microbial products themselves. The chapter sets the stage for the discipline of microbiology by outlining the importance of understanding the variety of microbial species (including bacteria, viruses, fungi, and protists), defining the field, and appreciating foundational contributions, such as Carl Woese's work in establishing the three-domain system for classifying cellular life.