Bacteria form a fundamental branch of life. They are the oldest forms of life and the most prolific of all living organisms, inhabiting every part of the Earth's surface, its ocean depths, and even such inhospitable places as boiling hot springs. In this Very Short Introduction, bacteriologist Sebastian Amyes explores the nature of bacteria, their origin and evolution, bacteria in the environment, and bacteria and disease. Amyes discusses some of the major infections caused by bacteria-bacteria causes pneumonia, diphtheria, cholera, and many other diseases-and shows how these pathogens avoid the defences of the human body. But the book looks at all aspects of bacteria, not just the negative side, stressing the key benefits of bacteria, which have been harnessed to preserve food, dispose of waste and to provide compost for horticulture. Indeed, life for man and for many animals would be impossible without bacteria. Amyes also offers a glance into the future, describing how bacteria might be manipulated to perform tasks that they previous were unable to perform and discussing the recent construction of a completely synthetic bacterial cell.