The aim of this research was preliminary ecophysiological survey of the cyanobacterium Lyngbya sp. FS33 Agardh which seems common strain in the paddy-fields and agricultural soils of Golestan Province and has not been characterized previously. The axenic culture has been enriched in to BG11 culture medium. Salinity, temperature, irradiance and pH treatments have been treated separately. Light treatments include 2, 30.60 micromolquanta.m-2.s-1 intensities and 2, 4, 6 and 8hours dark- light daily photoperiods. Salt treatments include culture medium without added salt to 1% NaCl, Temperature include 15oC to 45oC, alkalinity and acidity include pHs from 5 to 9, and carbon dioxide treatments include aeration, non aeration, and 1% carbon dioxide enrichment Survival, growth, specific growth rate, chlorophyll, phycoerythrin, phycocyanin, allophycocyanin, ammonium liberation, and phycobilisome potentiality, have been analyzed. Results showed that in the opposite of stigonematalean and nostocalean cyanobacteria, this strain show higher growth at 60 micromol quanta.m-2.s-1 intensity. Continuous 24 h illumination cause significant increase at the growth rate. Chlorophyll content show significant increase when salinity reach to 0.5%. Ammonium liberation seems higher amounts near to the optimum conditions and no significant differences moving slightly from the optimum. This srain be able to survive at low (100C) and high (450C) temperatures. At the optimum pH, significant increase in phycoerythrin content, reveal adaptation of photosynthesis apparatus with treated conditions. The phycobilisome structure seems complete at the optimum and incomplete at the extreme alkaline condition. Carotenoide production increase significantly at the first day of inoculation at the optimum acidity condition. As a whole, results introduce this strain, as the potent one for future biofertilizers beside heterocystous cyanobacteria.
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