The application of microbiological methods to the extraction of metals from minerals has definitely gained a prominent role and is supported by the several bioleaching and biooxidation processes operating in different sites over the world. In recent years new techniques and new results about proteomic and bioinformatics are bringing a new perspective on the microbial processes. This book focuses on the basic aspects of the process with special emphasis on recent contributions regarding the chemical and microbial aspects of the bioleaching process and the use of microorganisms in the treatment of complex ores and concentrates. It has been written by recognized researchers in order to introduce the main subjects of microbial processing to undergraduate and postgraduate students, scientists working in this field as well as interested industrialists.