Bacteria form a fundamental branch of life. They are the oldest forms of life as we know it, and they are still the most prolific living organisms. They inhabit every part of the Earth's surface, its ocean depths, and even terrains such as boiling hot springs. They are most familiar as agents of disease, but benign bacteria are critical to the recycling of elements and all ecology, as well as to human health.

In this Very Short Introduction, Sebastian G. B. Amyes explores the nature of bacteria, their origin and evolution, bacteria in the environment, and bacteria and disease. In this new edition, he examines the ethical implications of synthetic bacteria, the evolving technologies used to combat antibiotics resistance, and the role bacteria play in the evolutionary development of humans.