Escherichia coli is a versatile organism and very diverse. Members of this species vary from very pathogenic agents causing different types of diseases including meningitis, gastroenteritis, and septicemia, just to cite a few, to harmless organisms living in the intestines of both humans and animals. E. coli has also been used as a model organism for most bacteria except a few. For this reason, its study provides a huge advantage and can help understand the mechanisms involved in different processes such as pathogenesis, environmental disinfection, nutrient utilization, antibiotic resistance, and diagnostic/detection methods, and these are indeed the topics discussed in this book. The book has been divided into four main sections representing the different facets of E. coli applications, which include disease, biotechnology, environmental engineering and innovative approaches to detection, and lastly its physiology and cell biology. Such processes can be applied to the study of other organisms as well considering the development of diversity; for example, many organisms are capable of horizontal gene transfer, which is capable of increasing the fitness of the bacterial organisms involved and has a great impact on the control of such bacterial organism.