Query: NC_016930:228000 Rickettsia philipii str. 364D chromosome, complete genome
Lineage: Rickettsia philipii; Rickettsia; Rickettsiaceae; Rickettsiales; Proteobacteria; Bacteria
General Information: Rickettsiae are obligate intracellular Gram-negative bacteria mostly found in arthropods, some of which cause mild to severe diseases in humans. Spotted fever group rickettsiae (SFGR) cause disease in humans. R .philippi strain 364D, an SFGR, was isolated in 1966 from Dermacentor occidentalis ticks collected in Ventura county, California, and since then 364D has been detected in up to 11% of D. occidentalis from 8 California counties. It has now been recognized as causing eschar-associated illness.
Subject: NC_010628:675445 Nostoc punctiforme PCC 73102, complete genome
Lineage: Nostoc punctiforme; Nostoc; Nostocaceae; Nostocales; Cyanobacteria; Bacteria
General Information: The strain was isolated from a symbiotic association with the gymnosperm cycad Macrozamia sp. It typically grows in freshwater habitats. This genera of cyanobacteria are typically terrestrially-associated and are especially found in limestone or nutrient-poor soils. They are very similar to Anabaena spp. and historically they have been distinguished on the basis of morphological and life cycle characteristics. Nostoc spp. can grow heterotrophically or photoheterotrophically, and form heterocysts for nitrogen fixation. This organism can form nitrogen-fixing symbiotic relationships with plants and fungi such as the bryophyte Anthoceros punctatus. The relationship is relatively simple as compared to the Rhizobial symbiotic relationship. In the presence of the plant, hormogonia (short motile filaments) infect the plant, and then form long heterocyst-containing (nitrogen-fixing differentiated bacterial cells) filaments. The bacterial cell receives carbon sources in exchange for fixed nitrogen.