Book excerpt: Applied Microbiology and Molecular Biology in Oil Field Systems addresses the major problems microbes cause in oil fields, (e.g. biocorrosion and souring) and how beneficial microbial activities may be exploited (e.g. MEOR and biofuels). The book describes theoretical and practical approaches to specific Molecular Microbiological Methods (MMM), and is written by leading authorities in the field from both academia and industry. The book describes how MMM can be applied to faciliate better management of oil reservoirs and downstream processes. The book is innovative in that it utilises real industrial case studies which gives useful technical and scientific information to researchers, engineers and microbiologists working with oil, gas and petroleum systems.