ENVIRONMENTAL MICROORGANISMS: ECOLOGY AND APPLICATIONS highlights the significance of studying environmental microorganisms, which allows us to delve into the fascinating role these tiny organisms play in the functioning of Earth’s ecosystems, their responses to environmental changes, their taxonomic and functional diversity, and their numerous applications in biotechnology. Several chapters in this pedagogical and scientific book revolve around various educational tools. These tools include microbiological monitoring, microorganism cultivation, diversity and function study, and interactions with different ecosystems on Earth. A significant part of the content focuses on the analysis techniques used to study microbial biodiversity, including cultural, biochemical, and particularly molecular methods. The content highlights application tools like bioreactors, biofilm, wastewater purification, bioremediation, and composting. Students specializing in environmental microbiology, microbial ecology, and applied microbiology will benefit from reading this manuscript to enhance their understanding of the subject. The book is concise and succinct, serving as a valuable resource for not just students but also teachth an interest in microbiology.