The Natural History of Model Organisms: The unexhausted potential of E. coli Zachary D Blount Is a corresponding author

In 1884, the German microbiologist and pediatrician Theodor Escherich began a study of infant gut microbes and their role in digestion and disease. During this study, he discovered a fast-growing bacterium that he called Bacterium coli commune, but which is now known as the biological rock star that is Escherichia coli (Escherich, 1988; Shulman et al., 2007; Zimmer, 2008). E. coli's meteoric rise and exalted status in biology stem from how easy it is to find and work with. Hardy, non-pathogenic, and versatile strains that grow quickly on many different nutrients can be isolated from virtually any human. These traits made E. coli a mainstay in microbiology teaching lab collections. Consequently, when early 20^(th) century microbiologists cast about for a model organism, E. coli was one of the most widely available choices.

Those who chose to work with E. coli included Bordet and Ciuca (1921), Werkman (1927), Wollman (1925), Wollman and Wollman (1937) and Bronfenbrenner and Korb (1925), Bronfenbrenner (1932), who between them performed groundbreaking studies on bacterial physiology, viruses, and genetics (Daegelen et al., 2009). By the 1940s, its use in many foundational studies firmly established E. coli as the bacterial model organism of choice, making it the obvious organism to work with at the onset of the molecular biology revolution in the 1950s. As a result*,* it became the organism in which the most basic aspects of life, including the genetic code, transcription, translation, and replication, were first worked out (Crick et al., 1961; Nirenberg et al., 1965; see Judson, 1996 for an excellent history of early molecular biology and E. coli's role in it). The resulting knowledge and molecular methods for investigating and manipulating its biology have since led to E. coli's prominence in academic and commercial genetic engineering, pharmaceutical production, and experimental microbial evolution (see Box 1 for a glossary of specialist terms used in this article ), not to mention the biotechnology industry, which contributed $500 billion to the global economy in 2011 (Cohen et al., 1973, Schaechter and Neidhardt, 1987; Lenski, 2004; Bruschi et al., 2011; Kamionka, 2011; Huang et al., 2012; Kawecki et al., 2013). It is not hyperbole to say that E. coli is now the most important model organism in biology (Zimmer, 2008; see Box 2).