The present book is a joint effort made by contributors for their understanding on the microbes. We have presented the latest information lesson, well defined topics in a concise form. We have put in much hard work to make the matter, neither too elaborate so that we do not lose the interest of students nor too concise so as to leave vital topics uncovered. All lessons are written in simple language and is easy to understand even for beginners. The students, researchers and young microbiologist would be encouraged by this book and therein lies our happiness. As editors, we seek suggestions for further improvement; readers are welcome to contact us through mail, letter, and personal meet for any discussion, criticisms and suggestion in the way of further development in the subject.