The text book of Microbiology as taught in different courses in various universities. It has been divided in five sections. Sections I deals with the history of microbiology, taxonomy, morphology and reproduction of microorganisms, wherein, a brief account of eukaryotic microorganism is also discussed. Section II covers physiology wherein, a basic account of biochemistry and details of enzyme and metabolic processes in microorganisms is included. Further, certain techniques namely, ELISA and SDGC are also described. Section III deals with microbial genetics. Chapters 14 of this section starts with the basic terms used in genetics and description of nucleic acid. Besides microbial genetics transposable elements and transposition have been given. It also covers molecular biology. Section IV deals with Applied Microbiology. Human and Plant Diseases have been covered. Detailed account of Immunology, Soil Microbiology, and Industrial Microbiology has been included. Geomicrobiology has been treated specially in a chapter separately devoted to it. Section V covers techniques wherein, various types of microscopy, instrumentation and cultural techniques are given.