Nostoc punctiforme PCC 73102

Nostoc punctiforme is a nitrogen-fixing cyanobacterium, growing autotrophically with CO2 as the carbon source, utilizing an oxygen-producing photosynthetic mechanism for the generation of ATP and reductant. The order Nostocales grow as unbranched filaments and produce up to three kinds of differentiated cells. Heterocysts differentiate in response to the lack of nitrogen in the environment and are the sites of nitrogen fixation (3-10% of total cells). Nostoc species also produce relatively short, motile filaments called hormogonia and spore-like structures termed akinetes in response to nutrient limitation other than nitrogen. Nostoc species are widely distributed in illuminated portions of the biosphere, including fresh waters and tropical, temperate and polar terrestrial systems; they are rarely found in marine habitats. Growth is often as a colony of filaments within a gelatinous matrix. Many Nostoc species occur in symbiotic associations with fungi to form lichens and with representatives of each of the major phylogenetic groups of plants. They are major contributors to the sequestration of CO2 in organic compounds, especially in nutrient poor and extreme environments.N. punctiforme strain ATCC 29133 (also known as PCC 73102) has a complex life cycle with differentiation of heterocysts, hormogonia and akinetes. The strain was isolated from symbiotic association with the gymnosperm cycad Macrozamia sp. N.punctiforme grows rapidly under completely dark heterotrophic conditions, with sucrose, glucose or fructose as the carbon source. In addition to its symbiotic and heterotrophic competence, it is amenable to genetic manipulation. It contains an insertion element which pops out under certain growth conditions. When it pops out gene Npun_R0414, the nitrogenase molybdenum-iron protein alpha chain NifD, is put together in one piece (adapted from http://genome.jgi-psf.org/finished_microbes/nospu/nospu.home.html). (HAMAP: NOSP7)