Forty-two cyanoprokaryota strains were isolated from 10 diverse sites along Sharkia Governorate, Egypt (7 sites representing the fertile soils and 3 sites representing the new reclaimed soils). Eight genera and 11 species of N2-fixing cyanoprokaryota were identified based on available morphological distinction and physiological characterization. On the basis of the obtained results, we classified these isolates to 3 genera and 5 species isolated from fertile soils and 7 genera and 8 species isolated from new reclaimed soils. Nostoc spp strains were the most common filamentous heterocyst-forming cyanoprokaryota (22 strains) and two species of Nostoc including 11 strains of N. muscorum and 11 strains of N. calicicola. Anabaena includes 10 strains in three species (A. oryzae (6 strains), A. circinalis (2 strains) and A. oscillarioides (2 strains). Nodularia spumigena were represented in this work by two strains from fertile soils. In addition Calothrix clavata (2 strains), Synechococcus sp. (3 strains) and one strain of each Oscillatoria homogenea, Dermocarpa olivacea and Xenococcus kerneri were inhabited in the reclaimed soils. This indicates that Nostoc spp. and Anabaena spp. were highly distributed in fertile soils more than new reclaimed soils. The latter species were the most important cyanoprokaryota genera to fix atmospheric nitrogen in rice field.
Identification, Indigenous Cyanoprokaryota, Morphology, Nitrogenase Activity, Pigment Contents, Physiology.