NC_010628:1734000 Nostoc punctiforme PCC 73102, complete genome
Host 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.