Shaghayegh Iranshahi - MSc. student Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
Neda Soltani - Department of Petroleum Microbiology, Research Institute of Applied Science, ACECR, Tehran, Iran
Taher Nejad satari - Professor, Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
Shadman Shokravi - Associate prof., Department of Biology, Gorgan Branch, Islamic Azad University, Gorgan, Ira
Mehroz Dezfulian - Department of Biology, Karaj Branch, Islamic Azad University, Karaj, Iran

Cyanobacteria have a high morphological flexibility, so their identification is problematic. In this research, identification and morphological variability of indigenous cyanobacterium Anabaena sp. ISC ۵۵ Bory ex Bornetet Flahault (Nostocaceae) is investigated disciplines-wide. For this purpose, soil samples were cultured in BG۱۱۰ medium and Anabaena sp. ISC ۵۵, after isolation and treatment with different pHs (۵, ۷& ۹) and salinities (۰, ۱, ۲, ۳, ۴& ۵%), which then were followed biometrically and morphologically in solid and liquid medium via light and florescent microscope. Also, wall and cell variation was evaluated by scanning electron microscope (SEM). Morphological and molecular identification was carried out by valuable keys and ۱۶s rDNA partial sequencing respectively. The results indicated that morphological variation of Anabaena sp. ISC ۵۵ is dependent on the effect of pH and salinity. Biometric analysis implied that heterocyst and akinet shape is one of the most stable features and can be considered as a distinguishable character. The effect of pH is more highlighted in comparison to salinity. In salinities less than ۱% and alkaline condition, optimum condition for colonization is prepared and clump shape of colonies can be considered as a stable character. Molecular identification confirmed the morphological one.

Anabaena, SEM, Morphological variation, pH, Salinity, ۱۶s rDNA