Query: NC_000921:1007519 Helicobacter pylori J99, complete genome
Lineage: Helicobacter pylori; Helicobacter; Helicobacteraceae; Campylobacterales; Proteobacteria; Bacteria
General Information: This strain was isolated in 1994 in the USA from a patient with duodenal ulcer. This genus consists of organisms that colonize the mucosal layer of the gastrointestinal tract or are found enterohepatically (in the liver). It was only recently discovered (1983) by two Australians (Warren and Marshall) that this organism was associated with peptic ulcers. It is one of the most common chronic infectious organisms, and is found in half the world's population. This organism attacks the gastric epithilial surface, resulting in chronic gastritis, and can cause more severe diseases including those that lead to gastric carcinomas and lymphomas, peptic ulcers, and severe diarrhea. It is an extracellular pathogen that persists in the gastric environment, which has a very low pH, by production of the urease enzyme, which converts urea to ammonia and carbon dioxide, a process which can counteract the acidic environment by production of a base. The toxins include cytolethal distending toxin, vacuolating cytotoxin (VacA) that induces host epithelial cell apopoptosis (cell death), and the cytotoxin associated antigen (CagA) which results in alteration to the host cell signalling pathways. The CagA protein is translocated into host cells by a type IV secretion system encoded by the cag pathogenicity island.
Subject: NC_003888:4523500 Streptomyces coelicolor A3(2), complete genome
Lineage: Streptomyces coelicolor; Streptomyces; Streptomycetaceae; Actinomycetales; Actinobacteria; Bacteria
General Information: Well-studied antiobiotic-producing bacterium. These bacteria are widely distributed in nature, especially in the soil. 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 bacterium is a soil-dwelling filamentous organism responsible for producing more than half of the known natural antibiotics. It is a well-studied species of Streptomyces and genetically is the best known representative.