General Information: Soil bacterium producing an antituberculosis agent. The characteristic earthy smell of freshly plowed soil is actually attributed to the aromatic terpenoid geosmin produced by species of Streptomyces. There are currently 364 known species of this genus, many of which are the most important industrial producers of antibiotics and other secondary metabolites of antibacterial, antifungal, antiviral, and antitumor nature, as well as immunosuppressants, antihypercholesterolemics, etc. Streptomycetes are crucial in the soil environment because their diverse metabolism allows them to degrade the insoluble remains of other organisms, including recalcitrant compounds such as lignocelluloses and chitin. Streptomycetes produce both substrate and aerial mycelium. The latter shows characteristic modes of branching, and in the course of the streptomycete complex life cycle, these hyphae are partly transformed into chains of spores, which are often called conidia or arthrospores. An important feature in Streptomyces is the presence of type-I peptidoglycan in the cell walls that contains characteristic interpeptide glycine bridges. Another remarkable trait of streptomycetes is that they contain very large (~8 million base pairs which is about twice the size of most bacterial genomes) linear chromosomes with distinct telomeres. These rearrangements consist of the deletion of several hundred kilobases, often associated with the amplification of an adjacent sequence, and lead to metabolic diversity within the Streptomyces group. Sequencing of several strains of Streptomyces is aimed partly on understanding the mechanisms involved in these diversification processes.