This comprehensive book explores both the fundamental and practical aspects of microbial genetics, shedding light on viroids, viruses, phytoplasma, bacteria, fungi, and protozoa. Unveiling a fresh perspective, the book tackles traditional taxonomical debates by embracing DNA-based taxonomy, offering a novel approach to understanding phylogeny within this microbe realm. Furthermore, it delves into the exciting realm of metagenomics, revolutionizing the identification and classification of unculturable microorganisms. Written by leading experts, this essential reading material caters to students and researchers in Microbiology, Genetics, and Biotechnology.