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Abstract: Nostoc, widely distributed in cultivated soils, is one of the Cyanobacterial groups with filamental, hererocytous and autotrophic structures. This paper presents the results of isolating some Nostoc Cyanobacteria strains from selected cultivated soils in Nghe An province and evaluates their growth and nitrogen fixation for biomass production of bio-fertilizers. Five Nostoc strains were isolated, 3 of which looked blue-green (Nostoc calcicola HN9-1a, Nostoc linckia Cam-C1, Nostoc paludosum DT3-02) and the rest 2 looked brown (Nostoc ellipsosporum NH2X7, Nostoc gelatinosum TT3-05) in the white light. In BG-11 medium and neon light, the dried biomass productivity of the 3 blue-green strains (387 – 431 mg/L after 21 days of cultivation) was higher than that of the 2 brown strains’ (310 – 370 mg/L after 21 days of cultivation). These Nostoc strains are nitrogen fixing Cyanobacteria, which has been confirmed through detecting and sequencing their NifD gene and heterocyst formation. The results also show that the non-heterocyst Cyanobacterial strain, Pseudanabaena dictyothalla QV3-11, also isolated from the cultivated soil in Nghe An province, did not have the ability to fix nitrogen. The isolated nitrogen fixing Nostoc strains can be the subject of further research on bio-fertilizer production.
Keywords: Cyanobacteria, Nostoc, cultivated soil, growth, nitrogen fixation, NifD.
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