Query: NC_011896:3252925 Mycobacterium leprae Br4923, complete genome
Lineage: Mycobacterium leprae; Mycobacterium; Mycobacteriaceae; Actinomycetales; Actinobacteria; Bacteria
General Information: This strain was isolated from a human skin biopsy in Brazil, and passaged in nude mice and armadillos. The bacterium is a close relative of M. tuberculosis. However, compared to the latter, the genome of M. leprae is smaller due to reductive genome evolution, with many important metabolic activities including siderophore production, part of the oxidative chain, most of the microaerophilic and anaerobic respiratory chains, and numerous catabolic systems and their regulatory circuits eliminated due to extensive recombination events between dispersed repetitive sequences. It is evident that this species has undergone massive genome reduction over time as a result of its parasitic nature, discarding more than half its genes and rendering it the most striking example of genome reduction in a microbial pathogen.
Subject: NC_003155:5302280 Streptomyces avermitilis MA-4680, complete genome
Lineage: Streptomyces avermitilis; Streptomyces; Streptomycetaceae; Actinomycetales; Actinobacteria; Bacteria
General Information: This strain (ATCC 31267) was isolated and characterized in 1978 by R. Burg and colleagues from a soil sample collected in Shizuoka Prefecture, Japan. Antibiotic-producing bacterium. 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. This organism is a well known producer of the anti-parasitic agent avermectin which is widely used to rid livestock of worm and insect infestations and to protect large numbers of people from river blindness in sub-Saharan Africa.