Book excerpt: This book focuses on two key issues confronting humanity, viz., energy and environment. There is a need to devise strategies for protecting the environment, at the same time adequately meeting the ever-growing energy needs of the world. Harnessing the power of microbes is one step towards finding cheap, green and sustainable solutions to the problems of energy and environment. The book is divided into eight major topics. These topics include emerging trends in microbial biotechnology, harnessing sustainable energy sources from microorganisms, mechanistics of bioenergy production, bioenergy from wastes and pollutant removal, microalgae for biofuels, bioremediation technologies for petroleum hydrocarbons, polycyclic aromatic hydrocarbons and xenobiotics, bioremediation of nuclear wastes, and the role of extremophilic microorganisms in environmental cleanup.