This revised, up-dated and expanded edition of Professor Schlegel's well-established textbook provides an excellent introduction to microbiology for a wide range of undergraduate students. In addition to being a first-rate general introduction to the subject for all students of microbiology, it is also suitable for life-science students whose courses include microbiology as a component. These include students of biochemistry, botany, zoology, medicine, pharmacy and agriculture, as well as food science, biotechnology, ecology and environmental science. The text concentrates on the essential aspects of microbiology and thus provides the student with a broadly based overview of the subject. This new edition includes new species, new phylogenetic relationships and a greater emphasis on environmental and ecological matters, whilst retaining the traditional strengths of the previous edition.