Query: NC_017512:2087098 Neisseria meningitidis WUE 2594, complete genome
Lineage: Neisseria meningitidis; Neisseria; Neisseriaceae; Neisseriales; Proteobacteria; Bacteria
General Information: The second of two pathogenic Neisseria, this organism causes septicemia and is the leading cause of life-threatening meningitis (inflammation of the meninges, the membrane surrounding the brain and spinal cord) in children. This organism typically residies in the nasopharynx cavity but can invade the respiratory epthelial barrier, cross into the bloodstream and the blood brain barrier, and cause inflammation of the meninges. Pathogenicity factors include the surface proteins (porins and opacity proteins), and the type IV pilus (which is also found in Neisseria gonorrhoeae). This organism, like Neisseria gonorrhoeae, is naturally competent, and protein complexes at the cell surface recognize the uptake signal sequence in extracellular DNA, an 8mer that is found at high frequency in Neisseria chromosomal DNA.
Subject: NC_004061:540354 Buchnera aphidicola str. Sg (Schizaphis graminum), complete genome
Lineage: Buchnera aphidicola; Buchnera; Enterobacteriaceae; Enterobacteriales; Proteobacteria; Bacteria
General Information: This strain is the symbiont of the aphid Schizaphis graminum and contains a large circular chromosome. Aphid endosymbiont. Almost all aphids contain maternally transmitted bacteriocyte cells, which themselves contain bacteria called Buchnera. The aphids live on a restricted diet (plant sap), rich in carbohydrates, but poor in nitrogenous or other essential compounds. It is believed that the Buchnera provide the essential nutrients the host lacks. Besides a nutritional co-dependence, due to a co-existence of millions of years, Buchnera have lost the ability to produce cell surface components such as lipopolysaccharides. This makes for an obligate endosymbiont relationship between host and Buchnera. Buchnera are prokaryotic cells which belong to the gamma-Proteobacteria, closely related to the Enterobacteriaceae family. Phylogenetic studies using 16S rRNA indicate that the symbiotic relationship was established around 200-250 million years ago. Since Buchnera are closely related to Escherichia coli and Haemophilus influenzae, comparative genomic studies can shed light on the evolutionary mechanisms of intracellular endosymbiosis as well as the different underlying molecular basis between organisms with parasitic behavior and symbionts.