Query: NC_010628:3409000 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.
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General Information: These cyanobacteria are bluegreen algae that are capable of fixing carbon and nitrogen. They form long filaments and can be found worldwide in various aquatic environments as well as some terrestrial ones. These bacteria can form a variety of differentiated cell types, including spore-like cells (akinetes), small motile filaments (hormongia) and most importantly, heterocysts that are nitrogen-producing cells. The heterocyst produces multiple layers outside of its cell wall, shuts down photosystem II in order to inhibit oxygenic photosynthesis and ramps up metabolism in order to use up the oxygen present. Heterocysts donate fixed nitrogen compounds as amino acids to neighboring cells and in return receive a photosynthetically produced carbon source such as sucrose. These organisms produce toxic blooms in aquatic environments that are harmful or fatal to animals and humans due to the various cyanotoxins they produce. Anabaena variabilis is a filamentous heterocyst-forming cyanobacterium that fixes nitrogen and CO2 using the energy of sunlight via oxygen-evolving plant-type photosynthesis. In addition, this organism has been studied extensively for the production of hydrogen using solar energy.