Author: Dr. Rachana Choudhary
Volume: 01
First Online: 2026
Pages: 1-64
DOI:

This unit introduces viruses, bacteria, and actinomycetes as important groups of microorganisms with significant biological, medical, and industrial importance. It explains the origin, characteristics, structure, classification, morphology, and
replication of viruses, highlighting their obligate parasitic nature and role in causing infectious diseases. The unit further describes bacterial morphology, ultrastructure, cell wall composition, reproduction, nutrition, classification, and economic
significance, emphasizing their beneficial and harmful roles in agriculture, industry, and human health. It also covers actinomycetes, their morphological characteristics, classification, reproduction, and ecological importance, with special emphasis on their role in the production of antibiotics, enzymes, and other bioactive compounds.
Overall, this unit provides a comprehensive understanding of the diversity, structure, physiology, and applications of microorganisms, forming the foundation for advanced studies in microbiology, biotechnology, medicine, and environmental
sciences.