The discovery and development of antibiotics has been one of the most significant advances in medicine. In a golden era lasting from the 1940s to the late 1960s, antibiotic research provided mankind with a wide range of structurally diverse and effective agents for the treatment of microbial infections. Since then, actinomycetes, most notably members of the genus Streptomyces , have uninterruptedly proved to be a particularly rich source of antibiotics and other therapeutic and biotechnologically important compounds. This book brings together expert actinomycetologists to communicate the importance of finding novel antibiotic producing actinomycetes in extreme and marine environments in the light of molecular advances.