The first edition of this book has served its purpose satisfactorily. As its revision was overdue it has been revised adding topics like bacterial protein metabolism including its biosynthesis nucleic acids and their role in the genetic information and recombinant DNA technology. A number of figures tables and other useful informations have been added for the benefit.of the readers engaged in microbiology teaching and research. The book will continue to serve useful purpose for the students preparing for veterinary bacteriology and mycology and scientists serving at low ever levels.