Biodesulfurization (BDS) of fossil fuels has emerged as a promising alternative to the conventional hydrodesulfurization process for containment of sulfur oxide emissions during fuel combustion. The 4S pathway is a sulfur specific pathway that removes the sulfur atom from the recalcitrant organosulfur compounds present in fossil fuel fractions like diesel by oxidation. The end product is a sulfurless molecule, 2-hydroxybiphenyl. Though the process is very specific, however, speculations as to the bacterium’s organic solvent tolerance for effective BDS process are justified. This book focuses on the construction of genomic library of a biodesulfurizing bacterium in an organic solvent bacterium in an effort to enhance biodesulfurization of a model compound dibenzothiophene, by the recombinant bacterium.